Effects of Adding BreatheMAX-Assisted Deep Breathing to Home-Based Spot Marching on Maximal Voluntary Ventilation and Peak Expiratory Flow in Young Adults with Overweight or Obesity: A Randomized Controlled Trial

Highlights

Public Health Relevance—How does this work relate to a public health issue?

• Overweight and obesity represent critical global public health concerns that adversely affect respiratory mechanics and ventilatory function. This study addresses these issues by demonstrating that an accessible, home-based exercise and breathing regimen effectively enhances pulmonary outcomes in young adults (aged 18–25 years) with overweight or class I–II obesity. While our findings specifically emphasize the utility of early intervention in this young adult demographic, this low-barrier protocol offers a promising framework for future public health strategies targeting obesity-related respiratory impairment across broader age groups.

Public Health Significance—Why is this work of significance to public health?

• This work is significant because it evaluates a low-impact, home-based strategy designed to support ventilatory capacity without requiring specialized gym equipment or facilities.
• The Combined Spot Marching Exercise (SME) and BreatheMAX-assisted deep breathing (CSMEB) protocol demonstrated greater improvements in maximal voluntary ventilation (MVV) and peak expiratory flow rate (PEFR) compared to SME alone. Furthermore, the intervention was practical and well-tolerated with no reported adverse events during the 8-week trial, making it a feasible approach for young adults seeking targeted respiratory enhancements.

Public health implications—What are the key implications or messages for practitioners, policy makers and/or researchers in public health?

• The CSMEB program represents a practical, home-based strategy that could be integrated into community health initiatives to promote targeted respiratory endurance in young, relatively healthy adults with overweight or mild-to-moderate obesity.
• While body composition parameters remained unchanged over the 8 weeks, this study provides a foundation for future research into combined aerobic and resistive breathing modalities. Future long-term studies with larger cohorts, direct physiological measurements, strict nutritional controls, and diverse clinical populations are recommended to evaluate broader therapeutic utility and safety.

Abstract

Background: Overweight and obesity adversely affect respiratory mechanics and ventilatory capacity. This study evaluated the incremental effects of combined Spot Marching Exercise and BreatheMAX-assisted deep breathing (CSMEB) versus Spot Marching Exercise alone (SME) on pulmonary function in young adults with overweight/obesity. Methods: Thirty-eight participants (aged 18–25 years, BMI 25.0–39.9 kg/m²) were randomized into SME (n = 19) or CSMEB (n = 19) groups, with 36 completing the study (18 per group) after two withdrew before treatment. Both performed 30 min of SME 5 days/week for 8 weeks; CSMEB additionally performed daily device-assisted deep breathing (10 sets of 10 breaths). The primary outcome was maximal voluntary ventilation (MVV). Secondary outcomes included spirometry and body composition parameters. Results: At Week 8, CSMEB achieved significantly greater improvements in MVV compared to SME (adjusted mean difference = 6.31 L/min; 95% CI: 0.08–12.55; p = 0.047). Peak expiratory flow rate (PEFR) also significantly favored CSMEB (adjusted mean difference = 0.71 L/s; 95% CI: 0.02–1.39; p = 0.044). No significant between-group differences were found for FVC, FEV₁, FEV₁/FVC, muscle mass, or body fat percentage (p > 0.05). No adverse events occurred. Conclusions: Adding BreatheMAX-assisted deep breathing to a home-based SME program yields targeted enhancements in MVV and PEFR in young adults with overweight or obesity.

1. Introduction

Overweight and obesity increase respiratory resistance, impair diaphragmatic efficiency, induce muscle fatigue, and diminish endurance [1]. Structurally, overweight and obesity severely compromise respiratory mechanics and function; elevated intra-abdominal pressure restricts chest wall and lung compliance, leading to significant declines in expiratory reserve volume (ERV) and functional residual capacity (FRC). These alterations substantially elevate the risk of multiple comorbidities, including cardiovascular diseases, type 2 diabetes, and osteoarthritis [2,3,4]. This combination escalates the work of breathing, precipitating dyspnea and limiting cardiorespiratory fitness and overall quality of life [5]. Currently, moderate-intensity continuous training (MICT) and high-intensity interval training (HIIT) have gained substantial popularity. Both exercise modalities have been shown to reduce visceral adiposity and waist circumference, which are outcomes directly linked to enhanced respiratory function [6] and superior cardiorespiratory fitness [7]. Furthermore, integrating HIIT with MICT can synergistically improve maximal oxygen uptake (VO₂ max), respiratory capacity, and overall pulmonary function [6,8,9]. However, individuals with overweight and obesity frequently experience substantial joint load distress, particularly concerning the knee and hip joints, which increases the risk of musculoskeletal injury during high-impact exercises [10,11]. Moreover, standard aerobic modalities and HIIT protocols often depend on specialized equipment (e.g., treadmills or stationary bicycles), posing notable financial and logistical barriers to long-term exercise adherence, especially in home-based settings [12]. However, equipment-free HIIT options (e.g., bodyweight exercises) offer accessible alternatives. To promote long-term adherence and overcome space and equipment constraints, Spot Marching Exercise (SME) offers an accessible, low-impact variant of light to moderate-intensity continuous exercise (depending on the speed). Biomechanically, SME replicates daily ambulation through synchronized, continuous steps featuring hip flexion > 70 and shoulder elevation > 90. Physiologically, this concurrent multi-limb recruitment and thoracic stretching elevate the mechanical workload on inspiratory muscles, frequently eliciting moderate-to-severe dyspnea similarly to standard continuous aerobic modalities while minimizing joint stress [13,14,15]. While not intended to replace high-intensity or resistance training, SME provides a feasible, equipment-free alternative ideal for home-based exercise in individuals with overweight and obesity.

Inspiratory muscle training with resistance, such as Threshold IMT, achieved statistically significant improvements in maximal inspiratory pressure (MIP) and maximal expiratory pressure (MEP) compared to controls [16], while also enhancing 6 min walk distance [17]. Therefore, BreatheMAX, an inspiratory threshold loading device with volume-expansion feedback, may elicit greater respiratory muscle recruitment through sustained maximal inspiration (SMI) maneuvers in individuals with obesity. Commonly used in clinical rehabilitation for lung expansion and airway clearance, it enhances patient engagement through real-time audio-visual feedback, such as bubble sounds, which act as key motivators during training [18,19,20]. Although aerobic exercise and inspiratory training independently enhance pulmonary outcomes, whether combining home-based Spot Marching with an inspiratory threshold load with volume-expansion feedback device (BreatheMAX) yields synergistic gains in MVV and PEFR among young adults with overweight or obesity remains unexamined. Therefore, this study aims to compare the effects of combined SME and deep breathing training with the BreatheMAX device versus SME alone on maximum voluntary ventilation (MVV) and pulmonary function, in individuals with overweight and obesity. We hypothesized that adding a BreatheMAX device regimen to a home-based Spot Marching Exercise (SME) program would provide incremental improvements in MVV and pulmonary function compared with SME alone in young adults with overweight and obesity.

2. Materials and Methods

2.1. Study Design and Setting

This single-blind, randomized controlled trial investigated the comparative effects of combined Spot Marching Exercise and deep-breathing training (CSMEB group) versus Spot Marching Exercise alone (SME group) in adults with overweight and obesity. The trial took place at the Department of Physical Therapy, School of Integrative Medicine, Mae Fah Luang University (Chiang Rai, Thailand) from 1 December 2025 to 28 February 2026. Following written informed consent, participants were randomly allocated (1:1) to either the SME group or the CSMEB group using block randomization (block sizes of 2, 4, and 6) utilizing STATA version 10 (StataCorp LP, College Station, TX, USA). To ensure transparency and minimize potential bias, research team roles were clearly assigned: the random allocation sequence was generated by an independent researcher who was not involved in participant recruitment or assessment. To maintain allocation concealment, a clinical research coordinator handled sequentially numbered, opaque, sealed envelopes while also screening and enrolling eligible participants. Interventions were assigned and administered by an unblinded physical therapist, whereas outcome assessors and data analysts remained fully blinded to group assignments throughout the study. Primary and secondary outcomes comprising maximal voluntary ventilation (MVV), pulmonary function tests (PFT), and body composition were evaluated at two time points: baseline and week 8 post-intervention. The study protocol received ethical approval from the Mae Fah Luang University Ethics Committee on Human Research on 15 August 2025 (EC 25140-25). It was prospectively registered with the Thai Clinical Trials Registry on 18 November 2025 (TCTR20251118005).

2.2. Participants

Participants with overweight and obesity were recruited from Chiang Rai Province, Thailand, via social media campaigns and advertisement posters. Inclusion criteria were: male or female aged 18 to 25 years; a body mass index (BMI) ranging from 25.0 to 39.90 (kg/m²), classified as overweight to class II obesity; good postural balance control; absence of visual or auditory impairments; and the ability to effectively communicate and adhere to experimental instructions. Exclusion criteria included (1) a documented history or diagnosis of neurological disorders (e.g., epilepsy, stroke); (2) musculoskeletal conditions interfering with mobility (e.g., osteoarthritis, muscular dystrophy); (3) cardiovascular diseases (e.g., hypertension, myocardial infarction, or ischemic heart disease); (4) chronic respiratory diseases (e.g., asthma, chronic obstructive pulmonary disease (COPD)); (5) metabolic or endocrine disorders (e.g., type 2 diabetes mellitus); (6) current cigarette smoking status; (7) a recent respiratory tract infection within the preceding 4 weeks; (8) contraindications to pulmonary function testing; (9) orthopedic issues involving the knee, ankle, or other structural abnormalities that would impede Spot Marching Exercise; (10) abnormal resting vital signs, specifically a heart rate > 100 beats/min, blood pressure < 90/60 (mm Hg) or >140/90 (mm Hg), or a resting peripheral oxygen saturation (SpO₂) < 95%; (11) engagement in vigorous physical training within the past 6 months (defined as high-intensity running, cycling, or swimming for >30 min per session, 3 days per week, at an intensity of 70–85% of maximum heart rate (or eliciting dyspnea to the extent of speech limitation, or a Rating of Perceived Exertion (RPE) greater than or equal 15/20 on the Borg scale); (12) concurrent use of diuretics or anti-obesity/weight-loss medications; (13) During lactation/breastfeeding; or Participants with a self-reported history or clinical diagnosis of depression, anxiety, or severe psychological stress were excluded from the study.

2.3. Sample Size Calculation

The required sample size for this study was determined using an a priori power analysis in G*Power software (Version 3.1.9.6) (Heinrich Heine University Dusseldorf, Dusseldorf, Germany), utilizing the Means: Difference between two independent means statistical test. Based on an internal pilot study (n = 8 per group) comparing the SME and CSMEB group, the primary outcome (Maximal voluntary ventilation, MVV) data showed a mean of 6.74 (SD = 7.22) for the SME group and 17.25 (SD = 10.44) for the CSMEB group. These values resulted in an estimated Effect Size (Cohen’s d) of 1.17. With a two-tailed significance level of 0.05 and a statistical power of 0.90, the analysis required a minimum of 17 participants per group. To account for an anticipated 10% dropout rate, 19 participants were ultimately recruited for each group.

2.4. Outcome Measures

Blinded investigators assessed all participants at two time points: (1) before the intervention (baseline), and (2) after completion of the 8-week program (Week 8). The assessors were blinded to group allocation throughout the study to minimize assessment bias. For MVV and PFT assessment, all participants completed a dedicated familiarization session before formal baseline testing. During this session, participants practiced the MVV, PEFR, and spirometry maneuvers under the supervision of a researcher until correct technique and acceptable performance were achieved.

2.4.1. Primary Outcome

Maximal Voluntary Ventilation (MVV)

The study’s primary outcome was Maximal Voluntary Ventilation (MVV), assessed before and at week 8 post-intervention. Before testing each day, accuracy was verified using a 3 L calibration syringe according to the manufacturer’s instructions. MVV was assessed using a spirometer (Model Vyntus Pneumo, Jaeger Medical, Höchberg, Germany). MVV was evaluated in accordance with standardized guidelines [21]. Before testing, a trained researcher provided clear oral instructions and demonstrated the correct breathing technique to each participant. All measurements were conducted with participants in an upright seated position wearing a nose clip. Participants were instructed to form a tight seal around the mouthpiece, ensuring that the tongue and teeth did not obstruct the airflow. Following at least three baseline tidal breaths, participants performed rapid and deep breathing at maximal effort. Continuous enthusiastic verbal encouragement was provided throughout the maneuver to maintain optimal performance, with real-time feedback given to help participants sustain a targeted breathing rate of 90–100 breaths per minute. A test was deemed acceptable if performed with maximal effort, without air leakage, hesitation, or technical artifacts, and if the tidal volume (VT) during the maneuver exceeded the baseline resting VT. Each participant completed a minimum of two acceptable trials. If the variability between acceptable maneuvers exceeded 20%, additional trials were conducted. The highest value obtained among the acceptable efforts was recorded as the final MVV outcome (L/min). The MVV demonstrates good reliability for respiratory muscle endurance assessment, with reported Intraclass Correlation Coefficient (ICC) values ranging from 0.82 to 0.94 [22].

2.4.2. Secondary Outcomes

The secondary outcomes were forced vital capacity (FVC), forced expiratory volume in 1 s (FEV₁), the FEV₁/FVC ratio, peak expiratory flow rate (PEFR), muscle mass, and body fat percentage, assessed at baseline and week 8 post-intervention.

Pulmonary Function Testing (PFT)

Spirometry parameters were evaluated in strict accordance with the joint recommendations of the American Thoracic Society and European Respiratory Society (ATS/ERS) [23]. Before testing, a trained researcher provided clear oral instructions and demonstrated the correct breathing technique to each participant. All measurements were conducted with participants maintaining a standardized upright posture. Following the attachment of a nose clip and securing an airtight seal around the mouthpiece, participants performed initial quiet tidal breathing. All participants were instructed to inspire rapidly and completely to total lung capacity (TLC), holding their breath for no longer than two seconds. Subsequently, participants executed a forced expiration with maximal effort. During this phase, vigor, real-time verbal prompts (e.g., encouraging a forceful “blast” rather than a passive blow), and continuous body language cues were provided to facilitate maximal exhalation until complete emptiness was achieved. The operator closely monitored both participant effort and live graphical displays during testing. Immediately after full expiration, participants performed a maximal forced inhalation back to full capacity. The procedure was repeated for a minimum of three acceptable maneuvers (generally capped at eight attempts for adult subjects). FEV₁ and FVC were evaluated for repeatability after each attempt, with additional trials conducted as needed to satisfy standard ATS/ERS repeatability criteria. Each participant completed a minimum of three acceptable maneuvers separated by 1–3 min of rest between efforts. Acceptability and repeatability were established when the difference between the two largest FVC values must be ≤0.15 L, and the difference between the two largest FEV₁ values must be ≤0.15 L [23]. The highest (best) value for each variable among acceptable trials was selected for data analysis. Values were reported as absolute figures as well as percentages of predicted values (% predicted) based on standard reference equations. Spirometry demonstrates high reliability, with reported ICC values ranging from 0.97 to 0.99 [24]. Standard spirometry (FVC, FEV₁, FEV₁/FVC and PEFR) was always performed after MVV testing (at least 10 min of rest).

Body Composition

Muscle mass and body fat percentage were assessed using a multi-frequency bioelectrical impedance analysis (BIA) device (InBody 270, Biospace, Cerritos, CA, USA). To minimize measurement variability, participants strictly followed standardized pre-test instructions: fasting for at least 8 h, avoiding strenuous physical activity and alcohol consumption for 24 h, and refraining from excessive caffeine or fluid intake before testing. All measurements were conducted in the morning (between 8:00 AM and 10:00 AM) in a temperature-controlled room, and participants were instructed to void their bladder immediately before assessment. During measurement, participants stood barefoot on the four footplate electrodes while firmly gripping the handgrip electrodes, maintaining an upright posture with arms extended at a 30–45° angle from the torso. Following the automated scan, total weight, BMI, muscle mass, and body fat percentage were recorded [25].

2.5. Interventions: The Study Included Two Intervention Groups: The SME Group and the CSMEB Group

2.5.1. SME Group

The SME was implemented as a regulated light- to moderate-intensity continuous exercise (depending on the speed). Participants engaged in continuous stationary marching characterized by alternating steps and synchronized arm swings. Proper biomechanics required maintaining at least 90° shoulder flexion and at least 70° hip flexion (Figure 1), using visual marker lines marked on the wall as height references. Movement cadence was controlled using a pre-recorded metronome audio clip provided to each participant. Intensity was progressed by adjusting movement cadence: set at 70 individual steps/min in the first week and increased to 80 individual steps/min from weeks 2 through 8. Exercise intensity was maintained at or below 80% of the maximum heart rate (%HRmax) or a rating of perceived exertion (RPE) not exceeding 6 on a 10-point scale. The intervention spanned 8 weeks, with 30 min sessions performed 5 days a week. Following each session, perceived exertion was assessed using the modified Borg 0–10 scale. Before initiating the home-based program, all participants completed a structured supervised familiarization session. Under the direct supervision of a physical therapist, participants received detailed verbal explanations and physical demonstrations regarding proper posture, movement range, and synchronization with the metronome. Participants practiced under direct observation until correct execution was demonstrated. Movement cadence and joint amplitude were standardized for all participants, and all completed the prescribed protocol without requiring individual modifications or experiencing adverse events.

2.5.2. CSMEB Group

In addition to the SME protocol, participants in the CSMEB group underwent deep-breathing training using the BreatheMAX device (Figure 2), which was set at a constant water-regulated load of 5 cm H₂O throughout the entire 8-week intervention period. The BreatheMAX device functions as an inspiratory threshold loader with volume-expansion feedback. It features a 5 cm H₂O threshold load (determined by a 5 cm water column) combined with auditory bubbling feedback to promote maximal inflation. The breathing technique required participants to: (1) Sit upright with the chin slightly elevated and form a tight seal with their lips around the plastic mouthpiece. (2) Perform a slow, maximal inspiration through the device to generate volume-expansion airflow (evidenced by continuous water bubbling sounds) until reaching total lung capacity, followed by a 3 s breath-hold at peak inspiration. (3) Remove the mouthpiece and exhale normally. This maneuver was repeated for 10 repetitions per set, with a minimum rest period of 1 min between sets to prevent hyperventilation or dizziness. Participants performed 10 sets daily (totaling 100 breathing maneuvers per day), requiring approximately 20 min daily, 5 days a week for 8 weeks. A dedicated familiarization session was conducted to ensure proper device handling and breathing mechanics. For device hygiene, participants were briefed to replace the water after every session, wash the device thoroughly with mild dishwashing liquid, and air dry it. To further ensure sanitation and safety, the research team supplied a new, sterile device to each participant weekly. To enhance home-based adherence and autonomy, participants were permitted to choose the order of the two exercise modalities. A mandatory rest period until full physiological recovery (RPE 0/10 on the Modified Borg Scale) was required between activities to ensure participant safety and minimize fatigue. Additionally, both modalities had to be completed within a 2 h window to maintain the clinical relevance of a combined intervention, 5 days weekly over 8 weeks. Scheduled laboratory assessment follow-ups were conducted at the end of week 8.

2.5.3. Intervention Monitoring, Compliance, and Fidelity Verification

Participants in both study groups performed a standardized home-based training protocol. Intervention adherence, exercise compliance, and training fidelity were systematically monitored using three complementary methods: (1) Daily participant logbooks; (2) Weekly video clip submissions via a secure private messaging application (LINE); (3) Weekly follow-up telephone consultations conducted by the research team.

Participants submitted short video recordings (1–3 min per session) to enable direct verification of movement execution in the home environment. The Clinical research coordinator evaluated all video submissions against a standardized assessment checklist covering three key parameters (postural alignment, movement cadence, breathing mechanics), and real-time corrective guidance was provided via telephone or direct messaging whenever technical inaccuracies or improper execution were identified. All video audits and safety records were exclusively managed by an independent clinical research coordinator who was not involved in outcome assessments. Additionally, to protect participant privacy, all submitted media files were securely stored during the study and permanently deleted upon completion of the trial.

Safety monitoring was continuously performed throughout the 8-week trial period. Following each exercise session, participants were systematically screened for physical discomfort, atypical symptoms (e.g., RPE, dizziness or hyperventilation), and adverse reactions.

2.6. Statistical Analysis

Data were analyzed using the Statistical Package for the Social Sciences (SPSS) version 20.0 (IBM Corp., Armonk, NY, USA). Descriptive statistics, including mean, standard deviation, and percentage, were used to summarize participant characteristics, and the Shapiro–Wilk test was applied to assess the normality of data distribution. Within-group differences from baseline to post-intervention (Week 8) were evaluated using the paired-samples t-test for normally distributed data. To control for baseline differences, Analysis of Covariance (ANCOVA) was used to assess between-group differences at post-intervention, using baseline values as covariates. The ANCOVA assumption of homogeneous regression slopes was assessed. MVV was predefined as the single primary outcome of this study. All other outcomes (including PEFR, FVC, FEV₁, FEV₁/FVC, muscle mass, and body-fat percentage) were designated as secondary outcomes. No formal multiplicity adjustments were applied to the secondary analyses. The primary analysis was performed on a per-protocol basis. Statistical significance was established at an alpha level of p < 0.05.

3. Results

A diagram illustrating the flow of participants throughout the trial is presented in Figure 3. A total of 41 individuals were screened for eligibility, of whom 38 met the inclusion criteria and provided informed consent to participate. Participants were randomly allocated to either the SME group (n = 19) or the CSMEB group (n = 19). Before receiving the first treatment session, one participant from the SME group withdrew due to schedule conflicts (n = 1), while one participant from the CSMEB group withdrew because of personal reasons. These reasons were unrelated to the intervention. Therefore, the 36 completed the 8-week study protocol (n = 18 in the CSMEB group and n = 18 in the SME group) were included in the final per-protocol analysis set (

Table 1. Baseline Participant Characteristics.

Characteristic	Randomized (n = 36)
	SME (n = 18)	CSMEB (n = 18)
Age (years)	22.55 ± 1.04	22.66 ± 1.41
Gender (%)
Male	10 (55.6%)	9 (50%)
Female	8 (44.4%)	9 (50%)
BMI (kg/m2)	30.19 ± 4.47	29.78 ± 3.74
Heart rate (beat/min)	74.17 ± 9.84	69.5 ± 10.78
Systolic blood pressure (mm Hg)	126.17 ± 11.84	127.50 ± 13.97
Diastolic blood pressure (mm Hg)	82.11 ± 7.11	79.28 ± 7.74
Weight (kg)	87.01 ± 15.53	86.12 ± 20.61
Height (m)	170.11 ± 8.20	167.77 ± 10.66
MVV (L/min)	128.28 ± 24.22	123.88 ± 28.03
FVC (L)	4.17 ± 0.91	3.83 ± 0.89
FEV1 (L)	3.53 ± 0.77	3.35 ± 0.78
FEV1/FVC (%)	84.81 ± 6.14	86.71 ± 6.00
PEFR (L/s)	5.58 ± 1.84	6.12 ± 1.76
Muscle mass (kg)	30.63 ± 6.49	30.47 ± 8.24
Body fat (%)	36.79 ± 8.02	36.67 ± 5.85

Note: The data are expressed as mean ± standard deviation (SD); SME = Spot Marching Exercise; CSMEB = combination of SME and deep-breathing training; BMI = body mass index; MVV = maximal voluntary ventilation; FVC = forced vital capacity; FEV₁ = forced expiratory volume in 1 s, FEV₁/FVC = forced expiratory volume in 1 s to forced vital capacity ratio; PEFR = Peak Expiratory Flow Rate; mm Hg = millimeter of mercury; kg = kilogram; L/min = Liter per minute; L/s = liter per second; L = Liters.

). Two participants withdrew before intervention onset, and their data were excluded from all outcome analyses (a 95% completion rate among enrolled participants). The remaining participants in both groups completed all scheduled intervention sessions (40 of 40 sessions), corresponding to a 100% adherence rate among those who completed the study.

All outcome measures are summarized in

Table 2. Within-Group Comparisons of Pre-Post Test Using the Paired t-test.

Outcome	Groups	Baseline	Post-Test	Difference (95% CI)
MVV (L/min)	SME	128.28 ± 24.22	138.03 ± 23.22	9.75 * (5.86–13.81)
	CSMEB	123.88 ± 28.03	140.12 ± 29.68	16.25 * (11.32–21.18)
FVC (L)	SME	4.17 ± 0.91	4.26 ± 0.88	0.09 * (0.03–0.14)
	CSMEB	3.83 ± 0.89	3.98 ± 0.96	0.15 * (0.05–0.23)
FVC (% pred)	SME	93.83 ± 11.74	96.06 ± 10.42	2.22 * (1.01–3.44)
	CSMEB	87.67 ± 8.74	90.72 ± 8.88	3.06 * (1.68–4.44)
FEV1 (L)	SME	3.53 ± 0.77	3.60 ± 0.79	0.06 (−0.03–0.16)
	CSMEB	3.35 ± 0.78	3.42 ± 0.79	0.08 * (0.02–0.13)
FEV1 (% pred)	SME	92.78 ± 12.01	94.50 ± 12.78	1.72 (−0.79–4.24)
	CSMEB	88.71 ± 7.20	90.83 ± 8.02	2.11 * (0.80–3.42)
FEV1/FVC (%)	SME	84.81 ± 6.14	85.05 ± 6.37	0.24 (−3.41–3.89)
	CSMEB	86.71 ± 6.00	87.14 ± 6.19	0.42 (−1.15–1.99)
PEFR (L/s)	SME	5.58 ± 1.84	6.19 ± 1.82	0.59 * (0.04–1.15)
	CSMEB	6.12 ± 1.76	7.34 ± 1.81	1.22 * (0.76–1.68)
Muscle mass (kg)	SME	30.63 ± 6.49	31.12 ± 6.76	0.48 (−0.00–0.97)
	CSMEB	30.47 ± 8.24	30.54 ± 8.67	0.08 (−0.38–0.54)
Body fat (%)	SME	36.79 ± 8.02	36.21 ± 8.45	−0.58 (−1.45–0.28)
	CSMEB	36.67 ± 5.85	36.93 ± 6.14	0.27 (−0.53–1.06)

Note: Analyses were performed on the per-protocol population (n = 36; CSMEB group n = 18, SME group n = 18). The data are expressed as mean ± standard deviation (SD). SME = Spot Marching Exercise; CSMEB = combination of SME and deep-breathing training; MVV = maximal voluntary ventilation; FVC = forced vital capacity; FEV₁ = forced expiratory volume in 1 s; FEV₁/FVC = forced expiratory volume in 1 s to forced vital capacity ratio; PEFR = Peak Expiratory Flow Rate. L/s = Liter per second; L = Liter; kg = kilogram; CI = Confidence interval; * Significant improvement from baseline levels (p < 0.05).

and

Table 3. Adjusted Between-Group Comparisons of Post-Test Means Using ANCOVA.

Outcome	Week 8 (Post-Test)
	SME Means (95% CI)	CSMEB Means (95% CI)	Difference (95% CI; ηp2)
MVV (L/min)	135.92 (131.53–140.32)	142.24 (137.84–146.63)	6.31 * (0.08–12.55; 0.114)
FVC (L)	4.09 (4.02–4.17)	4.15 (4.07–4.22)	0.06 (−0.05–0.17; 0.036)
FEV1 (L)	3.50 (3.43–3.58)	3.51 (3.44–3.59)	0.01 (−0.10–0.12; 0.001)
FEV1/FVC (%)	85.62 (83.12–88.12)	86.56 (84.06–89.06)	0.94 (−2.62–4.49; 0.009)
PEFR (L/s)	6.41 (5.93–6.90)	7.12 (6.63–7.60)	0.71 * (0.02–1.39; 0.117)
Muscle mass (kg)	31.03 (30.59–31.47)	30.63 (30.19–31.07)	−0.40 (−1.02–0.22; 0.049)
Body fat (%)	36.15 (35.34–36.96)	37.00 (36.19–37.81)	0.85 (−0.29–2.00; 0.065)

Note: Analyses were performed on the per-protocol population (n = 36; CSMEB group n = 18, SME group n = 18). The data are expressed as mean (95% CI). SME = Spot Marching Exercise; CSMEB = combination of SME and deep-breathing training; ηp² Partial eta-squared values. MVV = maximal voluntary ventilation; FVC = forced vital capacity; FEV₁ = forced expiratory volume in 1 s; FEV₁/FVC = forced expiratory volume in 1 s to forced vital capacity ratio; PEFR = Peak Expiratory Flow Rate. L/s = Liter per second; L = Liter; kg = kilogram; CI = Confidence interval; * Significant improvement between groups (p < 0.05).

The primary outcome analysis using ANCOVA (adjusted for baseline values) revealed a statistically significant between-group difference in MVV, favoring the CSMEB group compared to the SME group (p = 0.047, adjusted mean difference = 6.31 L/min, 95% CI: 0.08–12.55). For secondary outcomes, Pulmonary Function Tests (PFT): Among secondary pulmonary function parameters, PEFR showed a statistically significant baseline-adjusted between-group difference favoring the CSMEB group (p = 0.044, adjusted mean difference = 0.71 L/s, 95% CI: 0.02–1.39). In contrast, no statistically significant between-group differences were observed for FVC, FEV₁, or FEV₁/FVC (p > 0.05 for all). Body Composition: There were no statistically significant baseline-adjusted between-group differences in body composition outcomes, including muscle mass and body fat percentage (p > 0.05).

Table 2 presents the within-group analysis, indicating that respiratory muscle endurance, measured via MVV, significantly increased in both the CSMEB group (from 123.88 ± 28.03 to 140.12 ± 29.68 L/min, p < 0.001) and the SME group (from 128.28 ± 24.22 to 138.03 ± 23.22 L/min, p < 0.001). For the pulmonary function tests (PFT), the CSMEB group demonstrated significant improvements in all parameters: FVC (p = 0.004), FEV₁ (p = 0.008), and PEFR (p < 0.001). In contrast, the SME group only showed significant increases in FVC (p = 0.002) and PEFR (p = 0.037). Body composition showed no statistically significant within-group differences for either muscle mass or body fat percentage. All participants completed the prescribed protocol as planned, without requiring individual program modifications. No adverse events or safety concerns were reported during the intervention.

4. Discussion

This study is the first to evaluate the incremental clinical effectiveness of combining BreatheMAX-assisted deep breathing with Spot Marching Exercise (CSMEB) compared to Spot Marching Exercise (SME) alone in individuals with overweight and obesity. Based on baseline-adjusted between-group comparisons at Week 8, the main finding is that the CSMEB regimen produced significantly greater improvements in MVV (p = 0.047) and PEFR (p = 0.044) than SME alone. In contrast, no statistically significant baseline-adjusted between-group differences were observed for other spirometry parameters (FVC, FEV₁, and FEV₁/FVC) or body composition outcomes, including muscle mass and body fat percentage. These findings suggest that the primary benefit of adding an inspiratory threshold loader with volume-expansion feedback breathing to a home-based Spot Marching program may lie specifically in enhancing respiratory endurance and peak expiratory airflow, rather than altering static lung volumes or overall body composition. Descriptively, both intervention groups exhibited post-intervention increases from baseline in MVV, FVC, and PEFR, with the CSMEB group additionally showing within-group changes in FEV₁. However, these within-group changes likely reflect general training adaptations, whereas only the baseline-adjusted between-group differences in MVV and PEFR demonstrate the added efficacy of the CSMEB regimen. Collectively, these results indicate that CSMEB represents a practical and feasible home-based strategy for targeted improvements in ventilatory capacity among young adults with overweight or obesity.

4.1. Effects of SME with Deep Breathing Exercise on MVV and PFT

Within-group analysis revealed that MVV improved significantly in both the CSMEB and SME groups, with relative increases of 13.1% and 7.6%, respectively. Intergroup comparisons further demonstrated that the CSMEB group experienced a significantly greater increase in MVV than the SME group, yielding a net difference of 5.5%. While a validated minimal clinically important difference (MCID) for MVV in healthy or overweight young adults has not been established, guidelines from Graham et al. (2019) indicate that typical measurement variability for this parameter ranges from 8% to 10% [23]. Accordingly, the 13.1% increase observed in the CSMEB group exceeds this expected technical variability, supporting a plausible physiological enhancement in ventilatory endurance beyond measurement error.

Regarding pulmonary function tests, FVC increased significantly within both groups (2% in SME and 3.9% in CSMEB). FEV₁ showed a statistically significant within-group elevation exclusively in the CSMEB group (2%), though the between-group difference was non-significant. PEFR increased significantly in both groups (10% in SME and 19% in CSMEB), and the between-group difference (Table 3). However, because established clinical thresholds for spirometry parameters are primarily derived from clinical populations with chronic respiratory disease or pharmacological trials [26,27], these observed changes in young adults without underlying respiratory illness should be interpreted strictly as physiological adaptations rather than definitive patient-important clinical benefits.

The findings of this study demonstrated that SME combined with breathing training led to significantly greater increases in MVV and PEFR in the CSMEB group compared to SME alone. These observed improvements may be partially attributed to the nature of the SME program, which serves as an aerobic exercise incorporating coordinated movements of both upper and lower extremities mimicking activities of daily living. Several interrelated physiological mechanisms have been hypothesized to potentially drive these respiratory adaptations: (1) Biomechanical effects of upper extremity movement: Performing unsupported arm elevation at a high angle during exercise increases the workload on the thoracic musculature, which might stimulate accessory respiratory muscles to facilitate rib cage elevation. (2) Intrathoracic pressure and volume dynamics: Continuous arm movement could enhance chest wall mobility, potentially expanding intrathoracic volume and airflow. (3) Respiratory muscle endurance adaptations: Prolonged and repetitive engagement of the chest muscles may induce functional adaptations that delay muscle fatigue during exertion [28,29]. (4) Thoracoabdominal interaction: High-angle leg movements synchronized with core activation might favorably alter pressure dynamics, potentially optimizing diaphragmatic excursion [30,31]. (5) Cardiorespiratory stimulus: Sustained limb movements elevate systemic oxygen demand, which may encourage a deeper, more regulated breathing pattern [32]. However, as these specific physiological indices were not directly measured in the present study, these underlying mechanisms remain speculative hypotheses. These trends align with findings reported by Azad and colleagues (2011) and Chaitra and Vijay (2011), who demonstrated that aerobic exercise training significantly improves pulmonary function and peak expiratory flow rate (PEFR) in overweight and obese students, as well as in healthy volunteers [33,34].

In addition, breathing training with the BreatheMax device, which provides a resistive load of 5 cm H₂O, might act as a repetitive breathing exercise. It is hypothesized that this could improve the overall efficiency of the respiratory system and facilitate deeper ventilation. Additionally, resistive breathing training may increase respiratory muscle strength—although muscle strength was not directly measured in the present study. These trends align with findings reported by Rekha et al. (2013) and El-Kosery et al. (2011), who observed enhanced respiratory performance, including inspiratory muscle strength, FEV₁, FVC [16] and maximal voluntary ventilation in postmenopausal asthmatic women [35] with chronic obstructive pulmonary disease [36] and in healthy subjects [37] after resistive muscle training. Conversely, our findings contrast with those of Womack and colleagues (2000), who investigated the effects of a 9-month aerobic exercise intervention combined with dietary restriction, reporting no significant differences in pulmonary function improvements compared to weight loss achieved through dietary restriction alone [38]. However, direct comparisons with these contrasting studies should be interpreted cautiously, as their non-significant findings may be attributable to age-related respiratory decline inherent to older cohorts, factors distinct from the physiological profile and intervention design of our younger adult population with overweight and obesity.

Importantly, the CSMEB group exhibited greater post-intervention improvements in MVV and PEFR compared to SME alone, suggesting a potential incremental benefit of incorporating inspiratory threshold load with volume-expansion feedback via the BreatheMAX device. However, participants in the CSMEB group received a higher overall intervention dose due to an additional daily deep breathing program (~20 min/session). Although both groups were equally monitored via daily logbooks and video submissions to minimize attention bias, between-group differences may partly reflect increased training volume, engagement, or expectancy effects rather than the isolated impact of the BreatheMAX device. Future studies should employ dose- or attention-matched control designs (e.g., sham breathing or time-matched relaxation) to confirm these findings.

4.2. Effects of SME with Deep Breathing Exercise on Body Composition

Following the 8-week training period, no statistically significant within- and between-group changes in body composition (muscle mass and %body fat) were observed in either the CSMEB or SME group (Table 2). The present results align with those reported by Ho et al. (2012), who evaluated a short-term (12-week), high-frequency aerobic exercise regimen in overweight or obese young adults and similarly observed non-significant changes in body composition, indicating that short-term exercise protocols may not suffice to elicit pronounced structural adaptations [39]. Furthermore, longer-term evidence from Willis et al. (2012) demonstrated that even a 32-week aerobic protocol failed to significantly augment muscle mass in the absence of concurrent resistance training [40]. The absence of statistically significant body composition modifications following this 8-week intervention can be attributed to several methodological factors: (1) Intervention duration and volume: An 8-week period primarily captures early neural and metabolic adaptations rather than substantial structural changes, and an exercise volume of ~150 min/week falls below the threshold recommended by the American College of Sports Medicine (ACSM) for significant fat loss (>250 min/week). (2) Exercise modality: Aerobic exercise alone offers limited hypertrophic stimulus compared to dedicated progressive resistance training. (3) Lack of strict dietary control: Participant nutrition was not experimentally manipulated or strictly monitored to guarantee a sustained energy deficit. (4) Study design limitations: Because both study arms engaged in active exercise without an inactive control group, a non-significant change in these parameters reflects true short-term stability or an absence of an effect rather than a proven physiological benefit. Consequently, whether a home-based Spot Marching program exerts any meaningful long-term influence on body composition in this population remains to be determined in longer-term trials with comprehensive dietary monitoring and appropriate control conditions.

4.3. Limitations of This Study

This study has several limitations. First, secondary outcomes were not adjusted for multiple comparisons. Although parameters like PEFR showed significant between-group differences, their p-values remain nominal. Future confirmatory trials specifically powered for these endpoints are recommended. Second, the sample size was based on an effect size from a small pilot study (n = 8/group). Thus, these preliminary findings warrant larger multicenter trials for confirmation. Third, uncontrollable lifestyle confounders (diet and physical activity) may have increased intersubject variability. Additionally, lacking a non-exercise control group limits separating intervention gains from learning effects. Future long-term trials should include dietary control, objective activity monitoring, and a sedentary control group. Fourth, this study did not evaluate subjective outcomes, such as dyspnea perception, daily physical functioning, or health-related quality of life. Future research incorporating these functional endpoints is recommended to evaluate the clinical relevance of the combined intervention fully. Fifth, potential physiological mechanisms (e.g., respiratory muscle strength, diaphragmatic excursion, or chest-wall mechanics) were not directly measured. Because MVV and PEFR are effort-dependent global metrics, improvements cannot definitively confirm specific neuromuscular or structural adaptations. Future studies incorporating direct assessments (e.g., MIP/MEP or electromyography) are needed to validate these mechanisms. Sixth, participant blinding was not possible due to the nature of the exercise intervention, which may have introduced performance bias. However, outcome assessors were strictly blinded to minimize assessment bias. Seventh, the study focused on young adults, restricting the age range to 18–25 years, which limits the generalizability of our findings to middle-aged and older adults with overweight or obesity. Eighth, body composition was assessed using bioelectrical impedance analysis (BIA), which presents methodological limitations compared with standard reference methods. Finally, despite no reported adverse events, the small sample size, short 8-week duration, and exclusion of severe comorbidities limit broad safety conclusions. Larger RCTs with longer follow-up are needed to verify safety and feasibility in higher-risk populations. However, this study has several notable strengths, including prospective trial registration, allocation concealment, rigorous assessor blinding to minimize assessment bias, a 95% completion rate among enrolled participants, and participants in both groups completed all scheduled intervention sessions (40 of 40 sessions), corresponding to a 100% adherence rate among those who completed the study.

5. Conclusions

This study demonstrates that an 8-week home-based intervention combining Spot Marching Exercise with BreatheMAX-assisted deep breathing (CSMEB) yielded greater improvements in MVV and PEFR compared to Spot Marching Exercise alone in young, relatively healthy adults with overweight or class I–II obesity. No adverse events were reported during the trial, and protocol adherence was high. Future studies involving larger sample sizes, longer intervention periods, and participants with clinical comorbidities are needed to establish broader safety and therapeutic utility. Given the small sample size, evaluation of multiple outcomes, absence of a sham-breathing comparator, and lack of patient-centered respiratory measures, these findings should be considered preliminary and require confirmation in larger, well-powered trials.