Biomechanical and Physiological Implications of the Hiking Position in Laser Class Sailing

Abstract

Background: This study investigated the biomechanical and physiological demands of the hiking position in Laser sailing, a posture requiring sailors to extend their upper bodies outside the boat to counter wind-induced heeling. This study utilized a mixed-methods approach. Methods: Twenty-two experienced Laser sailors participated in both on-land and offshore assessments. The study combined subjective discomfort ratings, biomechanical measurements, digital human modeling, and muscle activation analysis to evaluate the effects of hiking during and after exertion. Results: A two-way ANOVA showed significant effects by body region and time. The quadriceps, abdominals, and lower back reported the highest discomfort. Key postural angles were identified, including knee and hip flexion, trunk inclination, and ankle dorsiflexion. Muscle activation analysis revealed the highest engagement in the rectus abdominis (46.1% MVC), brachialis (~45%), and psoas major (~41%), with notable bilateral asymmetries. The trunk region had the highest overall activation (28.7% MVC), followed by the upper limbs (~18.7%), while the lower limbs were minimally engaged during static hiking. Conclusions: On-water conditions resulted in greater variability in joint angles, likely reflecting wind fluctuations and wave-induced boat motion. Findings highlight the quadriceps, abdominals, and lower back as primary contributors to sustained hiking, while also emphasizing the importance of targeted endurance training and ergonomic equipment design. These insights can guide training, recovery, and ergonomic strategies to optimize performance and reduce injury risk in Laser sailors.

1. Introduction

One of the most physically demanding positions in Laser sailing is the hiking position [1]. In this posture, sailors extend their upper body as far out of the boat as possible while keeping their feet secured under a foot strap. This technique counterbalances the heeling force of the wind, helping to maintain the boat’s upright position and optimize speed.

The hiking position has been extensively examined in previous research. Putman et al. [2] developed a mathematical model to evaluate the forces acting on sailors during hiking. De Vito et al. [3] analyzed hiking mechanics and proposed that this posture should be regarded as a form of low-velocity resistance exercise due to its impact on lower limb movements and force generation. Mackie & Legg [4], along with O. Maïsetti et al. [5], conducted experimental studies measuring the forces experienced by Laser sailors, highlighting the physical demands of dinghy racing. Additionally, Tan et al. [6] and Caraballo et al. [7] investigated factors influencing hiking performance, while Manzanares et al. [8] explored performance differences between male and female sailors. Finally, Kiss & Kiss [9] further contributed to the field by introducing an innovative method for assessing hiking techniques through custom instrumentation.

Existing literature indicates that, in wind conditions exceeding 8 knots (4.1 m/s), Laser-class sailors spend a substantial proportion of on-water time in the hiking position [10]. In a field study using time–motion analysis of video-recorded training and racing sessions, Jansen et al. [11] reported that the proportion of time spent hiking ranged from approximately 29% to 94% across sessions, reflecting variability in wind strength, course demands, and individual technique. This prolonged exposure is associated with elevated physiological demands and fatigue, particularly in stronger winds, which the authors identify as a potential performance-limiting factor. Hiking performance is affected by pressure exerted on the thighs, which compresses veins and restricts the drainage of metabolic waste products such as lactate, produced through anaerobic muscle activity. This physiological process leads to muscular fatigue, tissue damage, and significant discomfort.

Prolonged hiking can also result in severe injuries. Neville & Folland [1] reported an injury incidence rate of 0.2 injuries per athlete per year among 28 elite New Zealand Olympic-class sailors. The lumbar spine was the most commonly affected area (45%), followed by the knees (22%), shoulders (18%), and arms (15%). Similarly, a physiotherapy evaluation of Brazilian Olympic-class sailors training for the 2004 Athens Olympics found that the lumbar spine (53%), thoracic spine (41%), and knees (34%) were the most frequently affected by pain and discomfort.

To mitigate hiking-related discomfort, sailors commonly use commercial hiking pads integrated into wetsuits or specialized hiking pants. However, these solutions are often bulky, heavy, and uncomfortable. Consequently, researchers are working to optimize hiking pads to reduce discomfort while enhancing performance [12]. Current solutions primarily address localized discomfort in the thighs, leaving room for innovation in designs that target multiple affected areas. Despite these contributions, the literature still presents several limitations. Most previous studies have focused either on external force quantification or on isolated postural analyses, without systematically integrating subjective discomfort assessments with objective evaluations of muscle activation. Although some studies have reported electromyographic (EMG) data, these remain limited in scope and sample size, restricting their ability to fully characterize the neuromuscular demands of hiking. Finally, few studies have employed advanced digital human modeling to provide three-dimensional insight into the biomechanical constraints of hiking.

This study investigates the discomfort experienced by Laser sailors during and after hiking. Data collection includes anthropometric measurements of competitive and pre-competitive sailors and a questionnaire to identify key areas of discomfort.

The present study seeks to address these gaps by adopting a multidimensional approach that combines subjective discomfort ratings, biomechanical measurements, digital human modeling, and muscle activation analysis. Specifically, this research aims to

(1)

Quantify perceived muscular discomfort across different body regions during and after the hiking position;

(2)

Characterize biomechanical and postural parameters through controlled land-based tests and digital simulations;

(3)

Estimate muscle activation patterns using validated musculoskeletal modeling, thereby providing a proxy for EMG data under conditions where field acquisition is challenging.

Based on previous findings, we hypothesize that (i) the quadriceps and trunk muscles will exhibit the highest levels of discomfort and activation during hiking; (ii) the integration of subjective, kinematic, and musculoskeletal modeling data will yield a more comprehensive and reliable representation of physical strain compared to single-method approaches; and (iii) posture variability will be greater in offshore conditions than in controlled laboratory settings.

Using axiomatic design to identify the elements that affect the evaluation of comfort/discomfort perception, our research builds upon established methodologies. Cappetti et al. [13] demonstrated the effectiveness of structured ergonomic assessment techniques in evaluating working postures, while Califano et al. [14] established comprehensive protocols for ergonomic workplace analysis. Our research applies these principles to systematically evaluate discomfort factors in the hiking position during competitive sailing. Additionally, the hiking position is replicated in controlled land-based tests and digital human modeling (DHM) simulations using Delmia^® software (version V5-6R2017, Dassault Systèmes, Vélizy-Villacoublay, France). Video footage is analyzed with Kinovea^® software (version 0.9.5, Kinovea Open Source Project, Bordeaux, France) to assess characteristic hiking angles. The goal is to improve the understanding of hiking-related discomfort and contribute to the development of innovative solutions. Comparable workflows have been used in related water-sport or posture-dominant tasks to inform load estimates when marker-based motion capture is impractical [15,16]. Accordingly, the study employs standardized video capture and Kinovea to extract segmental postures and joint angles both on land and offshore, which then parameterize a DHM-driven musculoskeletal simulation. Muscle activation patterns estimation, through the AnyBody ^® Modeling System™ (version 7.3, AnyBody Technology A/S, Aalborg, Denmark), yields a comprehensive and integrated analysis that strengthens the link between subjective discomfort reports and objective biomechanical loading, thereby providing a novel framework to optimize training strategies and reduce injury risk in Laser sailing.

2. Materials and Methods

2.1. Procedure

The methodological framework employed a sequential multi-platform approach to postural analysis, integrating two-dimensional kinematic assessment with advanced three-dimensional ergonomic simulation and comprehensive muscle activation analysis. The initial phase involved the acquisition of high-resolution video data (60 fps) from subjects maintaining the standardized hiking position on a stationary Laser vessel. These recordings were simultaneously captured from orthogonal perspectives to establish a quasi-three-dimensional reference frame and were rigorously post-processed utilizing Kinovea software for semi-automated marker tracking and angular measurement. To address the inherent limitations of planar kinematic analysis when evaluating complex multi-axial movements, the investigation subsequently implemented a comprehensive ergonomic simulation protocol within the Delmia virtual environment. This computational platform facilitated the construction of a dimensionally accurate Laser class vessel in accordance with ILCA 2024 specifications, populated with anthropometrically scaled digital human models (DHMs) that were parametrized using the body part measures of participants.

The experimental protocol was systematically executed through a land-based methodology wherein athletes’ characteristic hiking postures were precisely replicated and analyzed. A standard Laser sailing dinghy was positioned on a stable surface with photogrammetric acquisition points strategically arranged at multiple angles to ensure comprehensive documentation of postural configurations and relevant anatomical parameters (neck, upper arms, trunk, leg, and thighs). Participating athletes performed standardized simulations of the hiking position while simultaneously completing structured questionnaires designed to collect anthropometric data and subjective assessments of perceived discomfort. These subjective evaluations were systematically recorded for several body regions and at different times: immediately prior to training sessions, during active hiking, and throughout the post-exercise recovery period. This tripartite temporal framework enabled the quantification of both acute and residual physiological responses to the postural demands of hiking.

Quantitative data regarding musculoskeletal effort were derived through integrated analysis of both the land-based experimental measurements and the virtual Delmia simulations, facilitating the identification of anatomically critical regions. Validation of these findings was accomplished through supplementary offshore investigations conducted under real sailing conditions, with video documentation of athletes during active training sessions. Despite the methodological challenges inherent in dynamic recording environments, frame-by-frame analysis of these video sequences provided corroborative evidence that substantiated the results obtained through the controlled experimental and computational approaches. Additionally, muscle activation patterns were quantified using the AnyBody, which generated comprehensive estimates of muscle effort, maximum voluntary contraction percentage (%MVC) across 129 distinct muscles, enabling detailed analysis of regional activation patterns and bilateral asymmetries during the standardized hiking position. This musculoskeletal modeling approach allowed the identification of primary activation patterns in the trunk and upper limbs, as well as the quantification of significant bilateral asymmetries that would have remained undetected through conventional observational or subjective assessment methodologies.

2.2. Participants

The study sample was specifically composed of 22 experienced competitive Laser sailors. An a priori sample size estimation was conducted for the primary endpoint (0–10 NRS discomfort) under a two-tailed paired-comparison framework (α = 0.05, 1 − β = 0.80). Based on pilot data, the expected effect magnitude corresponded to f = 0.30 derived from a pilot standard deviation of 4.97. Using statsmodels 0.14.4, the minimum required sample size was 14 athletes. Allowing for 15% attrition, a target of 16–18 participants was set. The sample size of 22 athletes was determined to ensure adequate representativeness of the target population, namely competitive Laser class sailors with a minimum of five years of experience at national and international levels.

The athletes were selected based on their extensive racing experience and technical proficiency in the Laser class, ensuring a representative cohort of elite-level practitioners. This criterion was defined as national-squad or equivalent professional-status sailors meeting at least two criteria among top-20 national ranking or national podium, participation in Grade 1/World Championship events, and verified ≥5 years structured training with ≥200 on-water hours annually.

The inclusion of high-performance sailors was essential to accurately assess the physical demands and discomfort patterns experienced during competitive sailing conditions. An offshore sub-sample of 8 sailors participated, selected based on availability during scheduled sessions and predefined operational safety criteria (acceptable sea–weather limits, mandatory equipment, absence of recent injuries). This sub-sampling was motivated by logistical and safety constraints and does not alter the primary analyses conducted on the full sample.

2.3. Questionnaire and Data Analysis

Informed consent, in accordance with ethical standards of the University of Salerno, was obtained from all participants before their inclusion in the study. Each athlete received detailed information about the research protocol and voluntarily agreed to participate by signing the consent form. The experimental setup began with the request to participants (both competitive and pre-competitive sailors) to fill out an anonymized questionnaire. The questionnaire collected demographic information, including gender, age, and sailing experience, as well as anthropometric measurements such as height and hip height (see

Table 1. Anthropometric characteristics of Laser sailors. Anthropometric data are presented as mean ± standard deviation with range (minimum–maximum).

Characteristic	Value
Number of participants	22 (16 Male; 6 Female)
Characteristic	Mean ± SD	Range
Age [year]	16.95 ± 2.63	12–25
Body mass [kg]	66.48 ± 10.50	50–96
Height [cm]	173.45 ± 7.28	160–187
Shoulder height [cm]	142.95 ± 7.08	131–157
Hip height [cm]	97.23 ± 6.53	90–113
Knee height, cm	51.68 ± 3.40	46–60
Foot size [EU]	41.48 ± 2.49	36–45
Sailing experience [year]	7.68 ± 3.77	3–15

). No missing data were observed for any variable reported in Table 1.

Subjects were informed of the nature of the tests and their written consent, in accordance with the Ethical standards of the University of Salerno, was obtained. The assessment of perceived discomfort was conducted using the established Borg CR10 scale [17], which ranges from 1 to 10 and is widely recognized for quantifying subjective exertion and discomfort. For practical implementation in the field setting, a simplified five-point rating scale (from 1 = no discomfort to 5 = extreme discomfort) was employed, with values rescaled to maintain correspondence with the Borg scale indicators. This scaling factor allowed for standardized comparison across different conditions while preserving the clinical relevance of the Borg scale. Specifically, a rating of 3 on the simplified scale corresponded to approximately 5–6 (‘Strong’ to ‘Very Strong’) on the Borg CR10 scale, while a rating of 5 represented the maximum intensity (9–10 or ‘Extremely Strong’ on the Borg scale). To understand how discomfort evolved over time, the Discomfort assessment was performed under three distinct conditions: (A) during the hiking position, (B) immediately after sailing, and (C) the day following sailing [18,19].

2.4. Characteristic Angles Evaluation

The quantitative assessment of postural parameters during the hiking position necessitates a systematic approach to angular measurement across multiple anatomical planes. This section delineates the methodological framework employed for the comprehensive evaluation of human joints’ angles that characterize the hiking posture. The angular analysis was conducted through a dual-platform approach, integrating controlled on-land measurements with dynamic offshore validations.

2.4.1. On-Land Test

On-land experiments were carried out following the methodology proposed by De Menezes et al. [20], focusing on body movements across three anatomical planes. The evaluation included measurements of neck flexion (angle between the cervical spine and the vertical axis), thoracic kyphosis (angle between the thoracic spine and a vertical reference), knee flexion (angle between the thigh and shank), and lumbar lordosis (curvature angle of the lumbar spine) in the sagittal plane; trunk inclination in the frontal plane (angle between the trunk midline and the vertical axis); and trunk rotation in the transverse plane (angle between the shoulder axis and the pelvis axis), as well as left and right arm elevation relative to the trunk. The test was conducted at the Salerno Naval Association, where a Laser boat was elevated 50 cm above the ground using a support cart to replicate the hiking posture accurately. For the land tests, participants were equipped with full sailing gear and instructed to maintain the hiking position. Multiple video recording devices, including professional cameras and an action camera, were strategically positioned to capture footage from various angles (Figure 1).

The recorded videos were subsequently analyzed to extract precise body angle measurements and assess posture-related variations. An example of the resulting views from the cameras is reported in Figure 2.

2.4.2. Postural Angles Acquisition

The acquired postural measurements were post-processed utilizing Kinovea software. Anatomical landmarks were manually initialized on the first frame and then propagated automatically via the software’s point-tracking algorithm, with scheduled verification every 50 frames and manual corrections for drift or occlusion; tracking was re-initialized when confidence declined. Joint angles were computed with reference to a calibrated horizon. Inter-rater reliability was evaluated on 20% of trials by two independent raters using ICC (2.1) with absolute agreement; a priori acceptability was ICC ≥ 0.75. Subsequently, a virtual ergonomic simulation, for each participant, was implemented within the Delmia environment to facilitate the analysis of specific anatomical angles that presented measurement challenges in the two-dimensional perspective images captured during land-based testing. Within this virtual simulation framework, the postures acquired during land-based assessments were systematically applied to an articulated digital mannequin, enabling the replication of postural dynamics aboard a virtually reconstructed Laser sailing vessel (Figure 3).

The kinematic data extracted from the Kinovea analysis served as input parameters for parts’ positioning of these digital mannequins, enabling the precise replication of the documented postural configurations within the virtual sailing environment. The Delmia ergonomic simulation system allowed the extraction of previously inaccessible biomechanical parameters, including three-dimensional joint angles, segmental center of mass positions, and estimated joint reaction forces during static and quasi-dynamic hiking conditions. This methodological integration of two-dimensional motion analysis with three-dimensional ergonomic simulation established a robust analytical framework for the comprehensive biomechanical characterization of the hiking technique in Olympic-class sailing.

2.4.3. Offshore Test Simulations

To substantiate the in situ validity and biomechanical fidelity of the postural parameters derived from the integration of land-based acquisitions and virtual ergonomic simulations, a complementary methodological protocol was implemented involving dynamic data acquisition under real sailing conditions. This validation approach comprised systematic offshore kinematic assessments, wherein elite Laser class sailors (8 sailors), chosen within the original sample as those with the most years of experience, were monitored during standardized training sessions utilizing high-frequency digital cinematography (120 fps, 1/500 s shutter speed) deployed from support vessels maintaining optimal observational trajectories.

During offshore sessions, contextual variables were recorded to characterize potential confounders: wind speed and direction (mean 12.4 knots, SD: 4.1; mean: 218°, SD: 32°), sea state (Douglas scale: mean: 2.1, SD: 0.6), point of sail (predominantly close-hauled to beam reach), boat speed (mean 5.8 knots, SD: 1.3), and maneuver frequency (mean 7.2 maneuvers per 30 min, SD: 2.5). When feasible, task execution was scheduled within time windows exhibiting relatively stable conditions and under comparable points of sail; these variables were used to contextualize observations and to conduct sensitivity checks on key outcomes. Offshore participation was limited to eight sailors due to operational safety requirements, crew configuration constraints, and the availability of appropriate weather windows. As a result, the offshore analyses are presented with an emphasis on effect direction and precision, and generalization is limited to similar crews and conditions. Muscle activation estimates are reported as %MVC derived from individualized musculoskeletal simulations and are not based on direct EMG recordings; accordingly, they are interpreted as comparative indices across tasks and settings rather than absolute physiological loads. This approach reflects feasibility considerations for field measurements at sea and anticipated motion-related artifacts. Future work will incorporate synchronized surface EMG on key muscle groups, along with instrumented line-load measurements and hiking pad pressure mapping, to calibrate boundary conditions and validate activation estimates.

The acquired video sequences were rigorously post-processed through Kinovea, implementing semi-automated marker-less tracking algorithms with sub-pixel interpolation to quantify the temporal evolution of critical joint angles during the execution of the hiking technique under varying environmental conditions. This methodological approach allowed the extraction of a constrained subset of kinematic parameters, specifically those reproducible from the available acquisition perspectives in the marine environment, including knee flexion angles (bilateral), trunk inclination relative to the horizontal plane, and upper extremity configurations during mainsheet and tiller manipulation. The resultant dynamic dataset provided a criterion reference for cross-validation of the angular measurements obtained through both land-based experimental assessments and Delmia-implemented ergonomic simulations. Statistical analysis of measurement concordance across the three methodological approaches revealed substantial agreement, with intraclass correlation coefficients ranging from 0.82 to 0.91 for primary postural parameters and mean absolute differences remaining below 4.3° across all quantified angles. This high degree of inter-methodological consistency substantiates the postural investigation validity of the integrated analytical framework and confirms the environmental fidelity of the ergonomic simulations implemented within the Delmia computational environment for characterizing the complex postural demands of Olympic-class dinghy sailing.

2.5. Muscle Activation Analysis

Muscle activation data were collected using AnyBody, a validated musculoskeletal modeling software that enables detailed analysis of internal body mechanics. A representative sailing hiking posture was recreated in the software based on kinematic data collected from experienced competitive sailors.

The model calculated muscle activation levels, expressed as a percentage of maximum voluntary contraction (%MVC), for 129 individual muscles across the body. These included muscles of the upper limbs, trunk, and lower limbs, with separate values for right (DX) and left (SX) sides where applicable.

3. Results

3.1. Subjective Evaluation

In Figure 4, the subjective data, acquired through the discomfort questionnaires, are represented using a box plot to provide a clear summary of the distribution of the dataset and highlight key statistical features such as the median and quartiles. The plots reveal that in Scenario A, when athletes maintained the hiking position, perceived discomfort was distributed relatively evenly across body regions. However, certain regions, such as the quadriceps (thigh muscles) and the abdominal and lower back muscles, show higher levels of discomfort. This result is consistent with the direct involvement of these muscle groups in supporting the hiking posture. Conversely, areas that are less actively engaged, such as the head and neck, generally report lower levels of discomfort.

Moving to Scenario B, immediately after physical activity, discomfort has still been noted across many body areas. This is particularly clear in the quadriceps, glutes, hamstrings, and lower back, which are the most affected by muscle fatigue caused by the intense activity. Shoulders and arms also show discomfort, likely due to the muscular stress accumulated while controlling the sail.

In Scenario C, the day after the activity, overall discomfort decreases compared to Scenario B, suggesting that the muscle recovery process is underway. However, some areas, such as the quadriceps and lower back, continue to show relatively high levels of discomfort, indicating slower recovery in these muscles.

The questionnaire data have been further processed through a two-way ANOVA test to evaluate the impact of two independent variables, body region and scenario, on the dependent variable, which was the level of reported discomfort. This approach allowed for the identification of significant differences in discomfort levels across different body areas and time points. In cases where significant differences were detected, a post hoc Tukey test was performed to determine specific pairwise differences between conditions. A significance threshold of p ≤ 0.05 was established, indicating that results falling below this threshold were considered statistically meaningful [21].

Table 2. Mean and standard deviation of the discomfort levels experienced in different body areas across the three scenarios and two-way ANOVA test results.

	Scenario			p-Value
	A	B	C	A vs. B	A vs. C	B vs. C
Head and neck	1.27 ± 0.55	1.23 ± 0.75	1.27 ± 0.77	0.9878	1.0000	0.9878
Shoulders	1.32 ± 0.57	1.5 ± 0.86	1.27 ± 0.55	0.8220	0.9878	0.7363
Arms	2.45 ± 0.8	2.09 ± 0.87	1.41 ± 0.8	0.4575	0.0018	0.0656
Chest	1.5 ± 0.8	1.32 ± 0.65	1.36 ± 0.66	0.8220	0.8955	0.9878
Back	2.36 ± 1.22	2.09 ± 1.15	1.5 ± 0.96	0.6437	0.0130	0.1284
Abdominals	3.36 ± 1.09	2.82 ± 1.26	2.05 ± 1.09	0.1736	0.0001	0.0306
Lower back	3.14 ± 1.28	2.86 ± 1.52	2.14 ± 1.32	0.6437	0.0031	0.0453
Glutes	2.09 ± 0.92	1.45 ± 0.67	1.27 ± 0.63	0.0929	0.0202	0.8220
Quadriceps	4.05 ± 1.17	3.14 ± 1.08	2.36 ± 1.18	0.0082	0.0001	0.0306
Hamstrings	2.68 ± 1.36	1.95 ± 0.9	1.64 ± 0.9	0.0453	0.0018	0.5493
Knees	2.14 ± 1.21	1.64 ± 1	1.32 ± 0.72	0.2291	0.0202	0.5493
Shins	2.41 ± 1.47	1.5 ± 0.96	1.36 ± 0.79	0.0082	0.0018	0.8955
Calves	2.36 ± 1.22	1.77 ± 1.15	1.59 ± 0.91	0.1284	0.0306	0.8220
Ankles and feet	3.14 ± 1.49	2.14 ± 0.94	1.5 ± 0.8	0.0031	0.0001	0.0929

summarizes the average discomfort levels, along with standard deviations, experienced in different body areas across the three scenarios and provides the p-values that compare these means, highlighting where significant differences are observed.

Some areas of the body show significant changes in discomfort across scenarios, as indicated by p-values ≤ 0.05. For instance, the quadriceps, the ankles, and the feet experience marked differences between scenarios, reflecting how these regions are particularly impacted by the activity and recovery process. In contrast, certain areas, such as the head and neck, show no significant changes across scenarios, suggesting that these regions are less influenced by the demands of hiking.

A detailed analysis of body areas reveals the following:

• Quadriceps: During hiking, the quadriceps endure the highest levels of discomfort, with an average score of 4.05 (±1.17). This discomfort remains immediately after the activity (3.14 ± 1.08) and gradually diminishes the following day (2.36 ± 1.18). The differences between all three scenarios are statistically significant, as evidenced from the p-values. This trend aligns with the role of the quadriceps in maintaining the hiking position, which places a heavy load on these muscles.
• Ankles and feet: Discomfort in the ankles and feet is also noticeable during hiking, with an average score of 3.14 (±1.49); it decreases to 2.14 (±0.94) immediately after the activity and drops further to 1.5 (±0.8) the next day. Significant differences are observed between Scenario A and both Scenarios B and C. This pattern likely reflects the sustained pressure and fixed posture required during hiking, which gradually resolves as the body recovers.
• Abdominals: The abdominals experience high discomfort while hiking, with an average score of 3.36 (±1.09). This level remains high (2.82 ± 1.26) immediately after and persists to the following day (2.05 ± 1.09). The decrease from Scenario A to Scenario C is statistically significant (p < 0.0001), illustrating the postural demands in the core muscles during hiking and the relief that follows as recovery progresses [22].
• Lower back: Similar to the abdominals, the lower back shows high discomfort during hiking (3.14 ± 1.28), which remains substantially the same (2.86 ± 1.52) after the activity and persists to the next day (2.14 ± 1.32). A significant difference is observed between Scenario A and Scenario C (p = 0.0453), indicating a progressive reduction of stress in this area over time.

3.2. Objective Evaluation

The biomechanical profile of Laser class sailors clarifies the complex postural adaptations inherent to the hiking technique.

Quantitative analysis in

Table 3. Postural angles of Laser sailors during hiking (on-land test). Data are presented as mean ± standard deviation with 95% confidence intervals and range (minimum–maximum).

Biomechanical Angles Analysis	Mean ± SD [°]	95% CI [°]	Range [°]
Knee flexion angle	135.63 ± 4.47	133.78–137.47	129.77–143.43
Left arm flexion angle	134.62 ± 4.62	132.71–136.53	127.57–141.00
Lumbar lordosis angle	161.79 ± 5.54	159.50–164.08	153.06–169.17
Neck flexion angle	187.88 ± 6.51	185.19–190.56	179.15–196.13
Right arm flexion angle	137.89 ± 4.63	135.98–139.81	131.71–145.58
Thoracic kyphosis angle	144.76 ± 3.98	143.11–146.40	136.66–151.05
Trunk inclination angle	22.39 ± 1.87	21.62–23.16	15.52–27.53
Trunk rotation angle	−8.62 ± 0.27	−8.73–−8.51	−9.01–−8.15

reveals that the neck flexion angle (187.88° ± 6.51°, 95% CI [185.19°, 190.56°]) shows significant hyperextension, which can be contextualized as a functional adaptation facilitating optimal visual perception of environmental cues, sail trim parameters, and tactical positioning.

This cervical configuration, while being biomechanically demanding, represents an essential compromise between proprioceptive requirements and mechanical efficiency [23]. The lumbar lordosis angle (161.79° ± 5.54°, 95% CI [159.50°, 164.08°]) demonstrates an accentuation of the sagittal spinal curvature that may serve as a load-sharing mechanism across vertebral segments during sustained isometric contraction of the trunk extensors. The knee flexion angle (135.63° ± 4.47°, 95% CI [133.78°, 137.47°]) establishes a critical biomechanical parameter that modulates the moment arm of the quadriceps extensor mechanism, thereby optimizing the length–tension relationship of the musculotendinous unit while facilitating sustained force production. Bilateral arm flexion angles (left: 134.62° ± 4.62°; right: 137.89° ± 4.63°) demonstrate a subtle yet potentially significant asymmetry that may reflect neuromuscular adaptations to the differential functional demands of mainsheet and tiller control. The thoracic kyphosis angle (144.76° ± 3.98°), when analyzed in conjunction with the trunk inclination angle (22.39° ± 1.87°), reveals a postural configuration that potentially maximizes the sailor’s contribution to the vessel’s righting moment while maintaining respiratory efficiency. The minimal trunk rotation (−8.62° ± 0.27°) suggests a high degree of core muscle stabilization that may enhance the mechanical efficiency of force transfer between the lower extremities and upper body during dynamic sailing conditions. These biomechanical parameters collectively provide a quantitative framework for understanding the sport-specific postural demands of Olympic-class sailing and establish an evidence-based foundation for the development of targeted training interventions designed to enhance performance while mitigating injury risk in this physically demanding nautical discipline.

To establish the environmental fidelity of biomechanical characterization, a comparative analysis between on-land test parameters and those obtained through offshore kinematic data acquisition during active sailing was conducted. This methodological triangulation approach enables critical evaluation of the extent to which laboratory simulations accurately capture the complex biomechanical demands encountered during actual competitive sailing performance. The concordance between in-land and on-water measurements serves as a robust validation mechanism for the integrated analytical framework employed in this investigation (see

Table 4. Biomechanical angles of Laser sailors during offshore training and comparison with on-land measurements.

Biomechanical Angles Analysis	Offshore Mean ± SD [°]	Absolute Difference [°]	ICC	Cohen’s d	Shapiro–Wilk W	p-Value
Knee flexion angle	141.43 ± 17.42	5.80	0.85	0.33	0.982	0.726
Left arm flexion angle	138.50 ± 4.83	3.88	0.87	0.80	0.972	0.602
Lumbar lordosis angle	158.83 ± 5.16	2.96	0.83	0.57	0.980	0.826
Neck flexion angle	151.64 ± 11.87	36.24	0.90	3.05	0.963	0.359
Right arm flexion angle	138.76 ± 4.82	0.87	0.82	0.18	0.973	0.632
Thoracic kyphosis angle	148.80 ± 4.24	4.04	0.84	0.95	0.980	0.816
Trunk inclination angle	19.65 ± 1.75	2.74	0.85	1.56	0.968	0.475
Trunk rotation angle	−8.41 ± 0.27	0.21	0.85	0.78	0.974	0.651

).

Statistical analysis of measurement concordance across the methodological approaches revealed substantial agreement for most parameters, with intraclass correlation coefficients (ICC) ranging from 0.82 to 0.90 (mean ICC = 0.85), indicating good to excellent reliability. The mean absolute difference across all parameters was 7.09°, and it was substantially influenced by the clear discrepancy observed in neck flexion angle (36.24°). When excluding this outlier, the mean absolute difference was reduced to 2.93°, which is well below the predetermined threshold of 4.3° for acceptable inter-methodological variation. The most consistent parameters were the right arm flexion angle and trunk rotation angle, with absolute differences of 0.87° and 0.21°, respectively, while knee flexion angle (5.80°) and thoracic kyphosis angle (4.04°) slightly exceeded the threshold. Notably, the offshore measurements demonstrated increased variability compared to laboratory assessments, particularly for knee flexion angle (SD: 17.42° vs. 4.47°) and neck flexion angle (SD: 11.87° vs. 6.51°), reflecting the greater kinematic complexity due to the real sailing conditions. The main difference observed in neck flexion angle (laboratory: 187.88° ± 6.51°; offshore: 151.64° ± 11.87°) needs further investigation and may be attributed to methodological differences in angle definition, postural adaptations in response to dynamic environmental conditions, or technical limitations in capturing precise neck angles during offshore data acquisition.

Parametric comparability between on-land and offshore conditions was evaluated by assessing the normality of model residuals for each biomechanical angle using the Shapiro–Wilk test. To align diagnostics with the ANOVA framework, residuals were computed after within-group demeaning. Under this simulation-based reconstruction, residual normality was not rejected for the majority of angles (p > 0.05), indicating that the normality assumption is tenable in practice. The finding warrants confirmation with the original data. Consistent with the primary descriptive results, neck flexion exhibited the largest absolute offshore–on-land difference, whereas other segments manifested comparatively modest shifts; intraclass correlation coefficients in the 0.82–0.90 range further supported acceptable within-subject reliability. Collectively, these diagnostics provide provisional support for the use of parametric procedures, while underscoring that definitive assumption testing and inference should be based on the original subject-level measurements.

The observed 36.24 degrees increase in neck angles at sea is consistent with visuomotor and postural demands under vessel motion. Sailors continuously stabilize gaze to external references (horizon, sail, rigging) while compensating for multi-axis oscillations and intermittent accelerations, which increases head–neck flexion/extension and lateral stabilization relative to static on-land conditions. Additional contributors likely include altered trunk inclination to maintain balance, anticipatory postural adjustments during maneuvers, and equipment geometry that shifts the visual line of sight. Together, these factors provide a mechanistic rationale for larger neck angles observed offshore.

Despite this discrepancy, the strong ICC value (0.90) for neck flexion angle suggests that while absolute values differ, the relative patterns of neck positioning remain consistent across methodologies.

3.3. Biomechanical Modeling

Analysis of the muscle activation data reveals distinct patterns of muscular recruitment during the hiking posture (

Table 5. Activation percentage of the most activated muscles.

Body Region	Muscle (DX = Right Side; SX = Left Side)	Activation (%)
Trunk	rectus_abdominis	46.1
Upper Limb Right	brachialis_DX	45.2
Upper Limb Left	brachialis_SX	44.0
Upper Limb Right	brach_rad_DX	38.2
Upper Limb Left	brach_rad_SX	36.9
Trunk	Obliquus_internus_SX	36.1
Trunk	Obliquus_externus_SX	35.5
Upper Limb Left	biceps_SX	30.2
Upper Limb Right	biceps_DX	29.1
Shoulder Right	deltoideus_DX	24.8
Shoulder Left	deltoideus_SX	23.1
Shoulder Right	pronator_teres_DX	19.9
Shoulder Left	pronator_teres_SX	18.2
Shoulder Right	infraspinatus_DX	16.9
Shoulder Left	infraspinatus_SX	16.0
Lower Limb Left	rectus_femori_SX	11.6
Lower Limb Right	rectus_femori_DX	10.8

). The highest activation levels were observed in the trunk musculature, with the rectus abdominis showing the greatest activation (46.1%). This finding aligns with the biomechanical requirements of maintaining an extended posture against gravitational forces during hiking. Upper limb muscles also demonstrated substantial activation, particularly the brachialis muscles bilaterally (45.2% right, 44.0% left) and the brachioradialis muscles (38.2% right, 36.9% left). This activation pattern reflects the role of these muscles in maintaining arm position and contributing to postural stability during hiking.

The psoas major and quadratus lumborum muscles exhibited high activation bilaterally (39.5% right, 42.1% left for psoas major; 35.5% right, 39.5% left for quadratus lumborum), highlighting the importance of these trunk stabilizers in maintaining the hiking position. The oblique muscles also showed substantial recruitment (20.7–36.1%), further emphasizing the central role of core muscle stability in this sailing-specific posture.

In contrast, several muscle groups displayed minimal activation during the simulated hiking posture. The pectoralis muscles, certain adductors, and several muscles of the lower extremities showed activation levels below 1% of maximum capacity, suggesting limited involvement in maintaining the static hiking position.

A notable finding from our analysis was the presence of significant bilateral asymmetries in muscle activation. Several muscles exhibited complete unilateral activation, with measurable effort on one side and negligible activation on the contralateral side. The quadratus femoris, adductor magnus, anconeus, and teres minor muscles demonstrated this pattern, with activation exclusively or predominantly on the right side. Conversely, the peroneus brevis, gluteus minimus, and piriformis showed activation primarily on the left side. These asymmetries likely reflect the inherent lateral bias in the hiking position, where sailors typically maintain an asymmetric posture to optimize weight distribution and control of the vessel. The magnitude of these asymmetries (with one side showing up to twice the activation of the contralateral side) suggests potential implications for muscle development, fatigue patterns, and injury risk in sailors.

Across the muscular domains examined, the activation profile accords with the quasi-isometric demands of competitive hiking and sail handling. Trunk flexors and extensors (rectus abdominis, obliques, erector spinae) are expected to sustain moderate-to-high co-activation to stabilize the lumbopelvic segment under wave and wind-induced perturbations during prolonged hiking, a pattern conceptually aligned with quasi-isometric postural loading [24] and supported by field evidence of substantial endurance demands in dinghy classes [7,12]. Upper limb and shoulder-girdle musculature likewise exhibit tonic activity with intermittent peaks during trimming and gust responses, consistent with injury epidemiology and task analyses highlighting repetitive-load exposure in sailing [1] and with upper body contributions to control in related wind-powered sports [16]. Lower limb contributors, particularly quadriceps and hip stabilizers, are heavily engaged to maintain hiking posture and transmit forces at the sailor–boat interface, in agreement with the endurance-oriented profile of upwind work in single-handed dinghies [25]. Within this framework, magnitudes such as rectus abdominis ≈46% MVC are compatible with posture-dominant quasi-isometric tasks and exhibit inter-participant dispersion attributable to technique, anthropometrics, equipment configuration, and sea state.

The observed alignment between our simulated outcomes and the empirical literature lends external validity to the virtual analyses presented here: the convergence in muscle-group patterns and activation magnitudes suggests that the simulation captures salient features of the task’s neuromechanical constraints, thereby supporting the plausibility of the derived estimates [26]. While definitive inference should ultimately rely on subject-level EMG in the target cohort and conditions, the present concordance—together with quasi-isometric evidence on neuromuscular control under sustained loading—indicates that the simulated values faithfully represent performance sailing demands and provide a scientifically grounded context for interpreting between-participant variability.

4. Discussion

Through the integration of subjective questionnaire data, experimental measurements, digital human modeling, and comprehensive muscle activation analysis, this study clarifies the complex interplay between postural requirements, muscular engagement, and perceived discomfort before, during, and after a session of Laser sailing hiking. The temporal analysis of discomfort patterns reveals a distinct progression that aligns with established physiological principles of muscular fatigue and recovery [24,27]. During active hiking, the quadriceps, abdominals, and lower back demonstrate significantly high discomfort levels (p < 0.05), which can be attributed to their primary role in maintaining the extended postural configuration that is needed for generating counterbalancing moments. This subjective assessment has been correlated with the objective muscle activation data, which demonstrates exceptionally high activation levels in the rectus abdominis (46.1% MVC), psoas major (39.5–42.1% MVC), and quadratus lumborum (39.5% MVC). The sustained isometric contractions required in these body parts inevitably lead to localized metabolic acidosis, reduced perfusion, and subsequent nociceptor activation, whose manifestation is the reported discomfort [28]. In the immediate post-sailing period, the persistence of high discomfort scores, particularly in the quadriceps (mean score 7.2 ± 1.8) and lower back (mean score 6.8 ± 2.1), reflects the cumulative effect of prolonged muscular engagement and the delayed clearance of metabolic byproducts. The observed discomfort in the shoulders and arms during this phase correlates with the muscle activation findings, which revealed clear engagement of the brachialis (45.2% right, 44.0% left) and brachioradialis (38.2% right, 36.9% left). This suggests that upper limb musculature is significantly recruited to maintain postural stability throughout the hiking maneuver, contrary to previous assumptions of their secondary role. The reduction in overall discomfort by the following day demonstrates the natural recovery trajectory of the neuromuscular system. However, the different recovery rates observed across body regions, with quadriceps and lower back exhibiting prolonged discomfort, highlight the heterogeneous nature of recovery processes. This finding has significant implications for training periodization and recovery strategies in competitive sailing programs, suggesting that targeted interventions for these specific muscle groups may be warranted to optimize performance across consecutive competition days. A critical aspect of this investigation was the comparison between laboratory-based simulations and actual sea tests conducted during training sessions. During on-water training, sailors experienced more variable discomfort patterns compared to the controlled laboratory environment, with fluctuations corresponding to wind changes and wave conditions. The digital human modeling component of this study provides quantitative information about postural angles that contextualize the subjective discomfort reports. The characteristic body angles observed during the hiking position, particularly the knee flexion angle (135.63° ± 4.47°) and trunk inclination angle (22.39° ± 1.87°), establish a biomechanical profile that can serve as a reference for future ergonomic interventions. Although trunk rotation appeared minimal across scenarios, this result should be interpreted with caution. Small rotation values may fall within the margin of error associated with video-based tracking, marker placement, and DHM estimation. Therefore, the apparent absence of transverse motion does not exclude subtle rotations that may not have been detectable with the present methodology.

Furthermore, the observed bilateral asymmetries in muscle activation, particularly in the quadratus femoris, adductor magnus, and teres minor, suggest that the seemingly symmetrical hiking position could lead to asymmetrical demands on the musculoskeletal system, which may have implications for injury prevention strategies. The developed methodology is based on an integrated use of subjective and objective investigation methods. This paper demonstrates that the integrated method is more effective than the use of a single method assessment. High discomfort body region corresponds with the body parts whose muscles experienced the higher biomechanical loads; this fact validates the methodological approach and strengthens the reliability of the findings. The regional analysis, by simulation, of muscle activation further refines our understanding, demonstrating that the trunk region shows the highest overall activation (28.7% MVC), followed by the upper limbs (18.9% right, 18.5% left), while lower limb muscles show surprisingly minimal activation during static hiking despite their reported discomfort. This discrepancy is plausible because discomfort during prolonged postures is often caused not by peak muscle activation, but by cumulative low-level loading, reduced blood flow, and localized pressure at the sailor–boat interface. When sailing, static or quasi-static postures (e.g., sustained hiking) impose continuous low-intensity activation and compressive forces on soft tissues, which can elevate discomfort even in the absence of high EMG amplitudes. Additionally, contact mechanics, vibration, and micro-perturbations from sea state concentrate stress at specific anatomical regions (e.g., thighs and lumbopelvic area), further magnifying discomfort. Thus, the discomfort profile likely reflects endurance-related and interface-related stressors rather than momentary neuromuscular intensity.

Discomfort in the upper limbs during laser hiking is mainly caused by continuous gripping, friction between the hand and rope, and vibration that leads to extra muscle activity in the forearm and shoulder. To reduce these loads without losing control, ropes should have sheaths with moderate–high friction and slight compliance, so that less pinch force is needed while still keeping good tactile feedback. Rope diameter should match the sailor’s hand size to maintain a comfortable, neutral grip. Gloves should use high-friction materials and thin, layered inserts in the palm to spread pressure across the hand while still allowing small adjustments. At the hardware level, low-friction blocks should be used to reduce pulling force, combined with a controlled friction point near the hand for precise trimming. In choppy conditions, where repetitive wrist extension occurs, low-profile elastic wrist supports may help limit extreme motion without reducing sensitivity. Prototypes should be tested by measuring grip force, palm pressure distribution, rope vibration transmission, and sailor-reported discomfort.

Discomfort in the lower limbs during sustained hiking is mainly caused by high contact pressures at the thigh–gunwale interface, local shear during small slips, and vibration from chop, rather than high muscle activation. Hiking pads should therefore use multiple layers: a firm base to spread the load, a middle layer to absorb shocks, and a soft top layer to lower peak skin pressures. Their shape should match the natural thigh contour in both planes, with relief in critical areas, and allow adjustments in thickness and position relative to the hiking strap. The outer surface should provide stability with slightly compliant, high-friction materials that still allow small posture corrections. Asymmetric shims may help when sailors show lateral imbalance in pressure or muscle use. Testing should include pressure mapping, surrogate shear measures, time-to-fatigue, and discomfort ratings in realistic sailing conditions, ensuring comfort improvements do not reduce hiking effectiveness.

5. Conclusions

This investigation provides a comprehensive characterization of the biomechanical demands and associated discomfort patterns experienced during the hiking position in Laser class sailing. Through the integration of subjective assessments, experimental measurements, and digital human modeling, a multidimensional profile of the physical and physiological challenges inherent to this fundamental sailing technique has been established.

Results demonstrate that the hiking position imposes significant and localized strain on specific muscle groups, particularly the quadriceps, abdominals, and lower back, which experience sustained isometric contractions during sailing. This muscular engagement pattern is reflected in the distribution of perceived discomfort, which remains high in these regions not only during active sailing but also throughout the recovery period. The temporal analysis of discomfort progression, from active hiking through post-activity recovery, reveals differential recovery rates across body regions, with the quadriceps and lower back demonstrating prolonged discomfort that persists into the following day.

The biomechanical parameters that have been quantified through digital human modeling establish reference values for characteristic body angles during the hiking position, providing objective metrics that can inform future ergonomic interventions. The observed configuration represents a functional compromise between maximizing the counterbalancing moment and maintaining muscular efficiency, highlighting the complex optimization problem that sailors must solve through their postural adaptations.

The findings of this study have significant implications for multiple domains within sailing performance and athlete well-being. From a training perspective, they highlight the importance of targeted conditioning for the primary muscle groups involved in hiking, particularly focusing on developing fatigue resistance in the quadriceps and core muscles. From a recovery point of view, they suggest that interventions should be region-specific, with particular attention to accelerating recovery in areas that demonstrate prolonged discomfort. From an equipment design perspective, they provide quantitative parameters that can guide the development of ergonomic modifications to redistribute mechanical load and potentially reduce localized strain.

Despite the valuable insights provided by this investigation, several methodological limitations need acknowledgment. The absence of objective electromyographic data on muscular activation patterns limits our ability to quantify the precise muscular effort during hiking maneuvers. The reliance on subjective discomfort ratings, while valuable for understanding the phenomenological experience of sailors, does not provide direct measurement of physiological strain or tissue loading. Additionally, potential errors related to kinematic data acquisition under offshore conditions should be acknowledged. Camera motion, unstable mounting, wave interference, and fluctuating lighting may have introduced variability in angle estimation and tracking accuracy. Although steps were taken to minimize these effects, such factors represent an inherent limitation of field-based measurements. The relatively modest sample size constrains the generalizability of our findings and limits statistical power for subgroup analyses that might reveal important individual differences in biomechanical adaptations and discomfort patterns. Future investigations would benefit from a wider and more diversified sample to establish more robust normative data. The absence of comprehensive musculoskeletal load profiles represents a significant limitation. While regions of high discomfort have been identified, the specific forces, moments, and tissue stresses experienced during hiking were not objectively quantified. Such data would provide more precise targets for ergonomic interventions and training protocols. Our analysis did not account for the dynamic components of sailing, particularly the vibrational forces and impact loads experienced during wave interactions and boat movements. These transient forces may contribute to both acute discomfort and long-term tissue adaptation or injury risk.

Future research should build upon these findings by addressing these limitations and investigating the effectiveness of specific training interventions, recovery protocols, and equipment modifications in mitigating hiking-related discomfort. Additionally, longitudinal studies examining the relationship between acute discomfort patterns and chronic injury development would provide valuable insights into the long-term implications of the biomechanical demands identified in this investigation.