Search Results (324)

Background: Targeted training interventions, including neuromuscular warm-up protocols, eccentric resistance training, and dynamic stretching exercises, with limited and heterogeneous evidence on recovery strategies, have shown potential benefits for muscle performance and reductions in injury risk. Objective: To synthesize and structure contemporary evidence on exercise-based interventions spanning the pre-activity warm-up through post-activity recovery, emphasizing performance outcomes, injury-related effects, reported dose–response patterns, and implementation characteristics. Methods: This systematic review with structured qualitative synthesis was based on a systematic database search and eligibility screening process (n = 40 studies). Studies evaluating exercise-based interventions targeting injury prevention and/or performance in athletes were included. Data extraction included study design, population characteristics, intervention components, outcomes, and risk-of-bias assessments, which were summarized using comparative tables and descriptive analyses. Due to heterogeneity, results were synthesized qualitatively without meta-analysis. Results: Neuromuscular warm-ups (e.g., FIFA 11+) were frequently linked to reduced reported lower-extremity injury risk, alongside improvements in sprint, jump, and balance performance. Eccentric hamstring training was linked in several studies to lower reported hamstring injury rates and increased eccentric strength and fascicle length, while dynamic warm-ups may acutely improve sprint and jump performance. Evidence regarding recovery modalities was heterogeneous, supporting a cautious and individualized emphasis on sleep, nutrition, and hydration. However, heterogeneity in study designs, outcome measures, and populations limits the comparability and generalizability of the findings. Conclusions: Exercise-based interventions, including neuromuscular warm-ups, eccentric strengthening, dynamic stretching, and progressive load and recovery strategies, may support performance enhancement and injury-risk reduction in youth and adult athletes when appropriately implemented, although interpretation is limited by study heterogeneity. Full article

Background: Conditioning activity (CA) is used to elicit post-activation performance enhancement (PAPE), but it is unclear whether load response principles from back squat models generalize to unilateral split squat conditioning when external load and surface instability are manipulated together. Thus, the current study examined acute effects of stable vs. unstable split squat CA with or without external load on jump performance and phase-specific electromyography (EMG). Methods: Twenty men completed a randomized crossover of three CAs (2 × 3 reps): unloaded stable split squat (SS), unloaded BOSU SS, and BOSU loaded at 50% split squat one-repetition maximum. Single leg jump (SLJ) and countermovement jump (CMJ) were assessed pre-CA and at 3 min (SLJ) and 4 min (CMJ) post-CA. EMG was recorded from the biceps femoris (BF), semitendinosus (ST), vastus lateralis (VL), vastus medialis (VM) gluteus medius (Gmed), peroneus longus (PL), gastrocnemius lateralis (GL) and gastrocnemius medialis (GM). Signals were time-normalized across the split squat cycle and quantified using phase-specific area under the curve (AUC) (descending/ascending). Results: SLJ and CMJ increased after all conditions compared with the pre-test (p < 0.05). SS and unloaded BOSU SS produced comparable jump outcomes, whereas BOSU loaded yielded the greatest CMJ increase (p < 0.04). Unloaded BOSU SS selectively increased hamstring activation (BF, ST) without changes in Gmed or PL. BOSU loaded increased EMG amplitude across all measured muscles. Conclusions: External load primarily drives acute CMJ potentiation, whereas instability mainly redistributes recruitment toward the hamstrings without improving jump performance beyond the stable condition. These findings indicated that when the goal is acute jump enhancement, external load should be prioritized, whereas unstable surfaces may be used to selectively target posterior chain activation. Full article

Background: We assessed the effects of a 6-week, low-volume Nordic hamstring exercise (NHE) intervention on hamstring flexibility, muscle mechanical properties and eccentric and isometric isokinetic knee flexion strength in recreationally active adults. Methods: Eighteen recreationally active adults were randomized into an NHE intervention group (IG; n = 9; females/males: 3/6; mean ± SD, age: 24.1 ± 1.3 years) and control group (CG; n = 9; females/males: 5/4; mean ± SD, age: 23.5 ± 1.8 years). The NHE intervention involved a progressive, supplementary training program performed initially one (weeks 1 and 2) and then two times per week over a 6-week period. The number of repetitions per session increased from 15 to 36 repetitions/week. The CG maintained their usual exercise routine over the same period. Standard goniometry, myotonometry, and isokinetic dynamometry (60°/s) were used to measure hamstring flexibility, muscle properties and isometric and eccentric isokinetic strength prior to and five days following the intervention. Results: The Linear Mixed Methods analysis identified a significant group × time interactions for isometric torque (IG: +5% vs. CG: −12%, p = 0.022) and flexibility (IG: +1% vs. CG: +7%, p = 0.023). Peak eccentric torque (IG: +7% vs. CG: −7%, p = 0.053) and muscle mechanical properties remained unchanged over the intervention period. Conclusions: Six weeks of low-volume NHE training marginally improved isometric and eccentric hamstring strength in recreationally active adults without changing hamstring flexibility or mechanical properties. The findings may have important implications for performance enhancement and hamstring injury risk reduction during high-intensity recreational sports. Full article

Research has yet to investigate the effects of unilateral Nordic hamstring training with a sloped platform (UNHT) on the fascicle length of the biceps femoris long head (BFlh FL) in previously injured legs. This study aimed to address this gap. A longitudinal pre–post design without a control group was used to examine the effects of 6 weeks of UNHT in eight young male athletes with a history of hamstring strain injury (HSI). Pre- and post-training measurements of middle and distal BFlh FL in the injured and uninjured legs were obtained using ultrasonography. At baseline, middle BFlh FL was significantly shorter in the injured leg than in the uninjured leg (86.0 ± 9.0 mm vs. 99.9 ± 7.6 mm, p < 0.001). Following UNHT, middle BFlh FL significantly increased in both the injured (105.8 ± 9.4 mm, p = 0.001) and uninjured legs (108.0 ± 10.3 mm, p = 0.596). Distal BFlh FL significantly increased in the injured leg (72.4 ± 7.1 mm to 85.7 ± 8.0 mm, p = 0.012), whereas the uninjured leg showed a smaller, non-significant change (72.8 ± 5.5 mm to 79.1 ± 7.5 mm, p = 0.069). These findings demonstrate that UNHT increased BFlh FL in previously injured legs. Because shorter BFlh FL and reduced eccentric strength are established risk factors for HSI, these adaptations may have implications for risk reduction; however, recurrence prevention was not assessed in this study. Full article

The aim of this study was to examine temporal changes in eccentric hamstring strength, impulse-based mechanical outputs, and interlimb asymmetry in professional football players performing a football-specific eccentric hamstring training program. Forty male football players (18–25 years) from two teams competing in the Turkish Second Professional Football League participated in this longitudinal cohort study. Eccentric hamstring performance was assessed at three time points (pre-, mid-, and post-season) using the NordBord Hamstring Testing System. Mixed-design repeated-measures ANOVA revealed significant main effects of time and significant time × Team interactions for left and right maximal impulse values (p < 0.05). In contrast, maximal eccentric force variables showed no significant time effects, although significant time × Team interactions were observed for both limbs (p < 0.05). Interlimb maximal force asymmetry and mean asymmetry demonstrated significant time effects, while Team effects and interaction terms were not significant. Overall, these findings indicate that temporal changes in eccentric hamstring performance in professional football players may be more clearly reflected in force–time–dependent metrics, particularly impulse, rather than peak force outputs. Accordingly, impulse-based measures may provide additional insight into eccentric hamstring performance changes in professional football players. Full article

This study investigated how varying body positions (seated, prone, supine) and knee joint angles (90°, 120°, 150°) influence the bilateral deficit (BD) in isometric hamstring strength. Thirty physically active participants (15 males, 15 females) performed unilateral and bilateral maximal voluntary isometric contractions (MVICs) across the tested position × angle conditions. Peak force (Fmax) and rate of force development (RFD) measures (RFDmax, RFD50 ms, and RFD200 ms) were recorded. Results indicated that the seated position elicited a greater bilateral deficit (i.e., lower BD ratios) than the prone and supine positions, with differences that were more pronounced at more extended knee angles. These findings underscore the importance of considering position- and angle-specific influences when assessing BD in hamstring strength. Clinicians and researchers should standardize testing protocols to ensure accurate evaluation and data interpretation. From an applied standpoint, the results support the development of resistance-training strategies aimed at enhancing hamstring function at long muscle lengths—an approach relevant to both performance optimization and injury prevention. Full article

Background: Hypertension is a multifactorial condition influenced by physiological, behavioral, and psychosocial factors. Muscle strength, physical activity, sleep quality, and perceived stress may contribute to blood pressure variability, although their relative influence remains unclear. This study examined associations between systolic blood pressure (SBP) and demographic, anthropometric, neuromuscular, behavioral, and psychosocial variables in adults with primary hypertension, with secondary analyses for diastolic blood pressure (DBP) and sex differences. Methods: A cross-sectional study was conducted in 391 adults with hypertension (165 men, 226 women). Predictors included age, body mass index, lower-limb muscle strength, physical activity (GPAQ), sleep quality (PSQI), and perceived stress. Associations were analyzed using correlation analyses and sex-stratified multivariable regression models. Results: In men, SBP correlated positively with age and negatively with lower-limb strength. In women, SBP showed associations with physical activity and perceived stress. Regression analyses indicated that sleep quality and perceived stress were independently associated with SBP in women (adjusted R² = 0.13), whereas hamstring strength was associated with DBP in men with low explanatory capacity (R² = 0.05). Moderate-to-high collinearity was observed among strength variables. Conclusions: Blood pressure variability was associated with neuromuscular and psychosocial factors with sex-specific patterns; however, the modest explained variance suggests these factors act as complementary rather than primary determinants. Longitudinal studies are needed to clarify causal relationships. Full article

Background: Chronic Achilles tendon ruptures present a major surgical challenge due to tendon retraction, degeneration, and large defects. Autologous hamstring tendon grafts have emerged as a reliable reconstructive option, yet their biomechanical consequences remain poorly understood. This study investigated whether Achilles tendon reconstruction with semitendinosus and gracilis autografts alters the plantar flexor moment arm and whether such changes affect muscle strength. Methods: A cohort of 25 patients (mean age: 44.5 years) underwent minimally invasive endoscopic reconstruction using hamstring autografts. This secondary salvage procedure was performed in patients with neglected ruptures or failed primary treatment. Five patients were excluded from the original intervention group due to inadequate radiographic quality. Radiographic measurements of the Achilles tendon moment arm and isometric plantar flexor strength assessments were performed at 12 and 24 months postoperatively. Statistical analyses included paired t-tests, Wilcoxon signed-rank tests, and correlation analyses. Results: Results showed a significant shortening of the Achilles tendon moment arm after reconstruction compared with the preoperative imaging length (mean reduction: 6.6 mm; p < 0.0001). Despite this, plantar flexor strength in the operated limb improved significantly over time at 12 and 24 months (+388.6 N at 24 months; p = 0.0067) and did not correlate with the degree of moment arm shortening (p > 0.3). By 24 months, the operated limb demonstrated comparable or greater strength than the contralateral side, with nearly half of the patients achieving substantial clinically meaningful improvements. Conclusions: In conclusion, Achilles tendon reconstruction with hamstring autografts leads to consistent moment arm shortening, yet this does not impair long-term restoration of plantar flexor strength. A progressive rehabilitation program extending up to two years appears essential to optimize recovery and compensate for biomechanical alterations. Full article

Background: Physical functional capacity plays a critical role in sports performance and changes markedly from adolescence to adulthood. This study aimed to compare the physical functional characteristics between adolescent and collegiate soccer athletes. Methods: Fifty elite male soccer athletes (30 adolescents, 20 college students) were assessed for joint range of motion, muscle flexibility, dynamic balance, and trunk functional capacity. Results: Adolescent athletes achieved significantly greater general joint laxity score than collegiate athletes (p = 0.01), with significantly greater hip range of motion across all planes (abduction, internal rotation, and external rotation; all p < 0.01). College athletes had significantly lower SLR degree (left: p < 0.01, right: p < 0.05) but significantly greater degrees on passive Ely’s test (p < 0.01) than adolescent athletes. Collegiate athletes delivered significantly superior dynamic balance performance in the Y-balance test, particularly in the posterolateral and posteromedial directions (all p < 0.05). Unexpectedly, trunk functional capacity was significantly lower in collegiate athletes compared with adolescents (p < 0.01). Limb asymmetry was observed in both groups: collegiate athletes showed asymmetry only in the anterior reach direction of the Y-balance test (p = 0.018), whereas adolescents exhibited asymmetry across multiple joints (ankle, hip, hamstrings, and quadriceps; all p < 0.05) and in the posterolateral direction of the Y-balance test (p < 0.01). Conclusions: Adolescent athletes demonstrated significantly superior joint range of motion and lower limb flexibility, whereas collegiate players exhibited better balance performance, indicating distinct functional profiles between the two cohorts, which may be associated with differences in training experience and developmental stages. Full article

Background and Objectives: Anterior cruciate ligament (ACL) reconstruction (ACLR) is widely performed to restore knee stability and facilitate return to activity. However, recovery of muscle strength, balance, functional performance, and patient-reported outcomes does not occur uniformly over time. The longitudinal recovery trajectory across various functional areas during the first year after ACLR remains insufficiently characterized. Materials and Methods: We included 107 patients who underwent isolated unilateral ACLR using a hamstring autograft. Isokinetic knee extensor and flexor strength, postural stability, Y-Balance Test (YBT) performance, and subjective knee function scores were assessed post-injury (approximately six weeks after ACL injury and prior to ACLR) and at 3, 6, and 12 months postoperatively. All patients followed a standardized postoperative rehabilitation protocol. Results: Knee extensor strength deficit worsened at 3 months and remained present at 12 months. In contrast, knee flexor strength deficit decreased progressively and reached near-symmetrical values by 12 months. Sway path length decreased significantly over time in both limbs. In the operated limb, improvements plateaued after 6 months, and limb symmetry indices approached symmetry by 12 months. YBT limb symmetry indices demonstrated a non-linear recovery pattern. Anterior, posterolateral, and composite scores decreased at 3 months, recovered to post-injury levels by 6 months, and showed significant improvement at 12 months. Posteromedial reach did not decline at 3 months and improved significantly only at 12 months. Subjective knee function scores (Lysholm and IKDC) did not differ significantly between post-injury and 3-month assessments, but improved significantly from 6 months onward. Tegner activity scores gradually increased and returned to pre-injury levels by 12 months. Conclusions: Recovery after ACLR is prolonged and non-synchronous. Quadricep strength remains incompletely restored at 12 months, whereas hamstring strength recovers more favorably. Balance, functional performance, and subjective outcomes improve mainly after 6 months. These findings support the need for prolonged rehabilitation and serial, multidimensional functional assessments beyond time-based criteria. Full article

Knee biomechanical demands vary across different sports due to sport- and position-specific patterns of muscle recruitment. To return to performance, athletes must adequately restore knee kinematics to regain control over the same sport mechanics that led to the initial anterior cruciate ligament (ACL) injury. ACL graft selection should therefore minimize donor site morbidity and support sport-specific demands. This study aims to address the available evidence and guide surgical graft choice in athletes. A literature search of PubMed, MEDLINE, Scopus, and Web of Science (up to September 2025) assessed BPTB, hamstring, and quadriceps tendon autografts. Outcomes included revision, graft survival, return to sport, time to return, PROMs, anterior knee pain, donor site morbidity, and prognostic factors (age, sex). Sports were classified as pivoting, contact/collision, or endurance/non-pivoting. The results were synthesized narratively. In pivoting and cutting sports, bone–patellar tendon–bone (BPTB) autografts offer high survival rates but are associated with a high incidence of anterior knee pain, which is a substantial drawback in kneeling or flexion-intensive sports. Hamstring tendon (HT) grafts carry higher revision rates in female and younger patients, though they have low donor site morbidity that does not appear to affect long-term athletic performance. Quadriceps tendon (QT) grafts are emerging as a promising option for pivoting athletes. However, conflicting results indicate that the revision risk is comparable to that of HT grafts and possible long-standing extensor mechanism weakness. Contact and collision sports demonstrate similar trends, but kneeling and contact injuries are more common in this group. Thus, while prioritizing powerful hamstring strength, anterior knee pain symptoms should still be carefully considered. The diameter of the HT autograft should exceed 7.5 mm to ensure comparable revision outcomes with BPTB. QT grafts remain a limited-evidence attractive option. Endurance and non-pivoting athletes require fewer pivoting mechanics but rely heavily on muscle symmetry and repetitive motion. BPTB grafts are less suitable in this category due to alterations in sprint mechanics, muscle asymmetry, and repetitive patellofemoral joint loading. HT grafts provide favorable rates of return to sport, whereas evidence regarding QT graft use in non-pivoting athletes remains limited. Full article

Background/Objectives: Knee osteoarthritis (KOA) is associated with pain, functional decline, and altered biomechanics. The Step-Up and Down-Forwards (StUD-F) task provides an ecologically relevant assessment of challenging movements. This study investigated neuromuscular activation and lower-limb kinematics of leading and trailing-limbs during the StUD-F in individuals with KOA. Methods: Forty participants with KOA (65.3 ± 7.68 years; 21M/19F; BMI 28.9 ± 4.52 kg/m²) completed a 25 cm box StUD-F task. Surface electromyograph recorded bilateral activation of the vastus medialis (VM), vastus lateralis (VL), bicep femoris (BF), and semitendinosus (ST). Triplanar hip, knee, and ankle joint angles were estimated using inertial measurement units. StUD-F events (initial stance; step contact; ascent completion; descent preparation; step-down touchdown; and descent completion) were identified using custom algorithms. Pain was assessed using visual analogue scales and the Knee Injury and Osteoarthritis Outcome Score (KOOS). Limb differences were analysed for leading or trailing roles using paired samples t-tests or non-parametric equivalents; waveforms were visually inspected. Results: Distinct neuromuscular and kinematic asymmetries were observed when affected and contralateral limbs were compared within each role (leading/trailing). During step-up, the affected leading limb demonstrated higher quadriceps activation at initial stance (VM: p = 0.035; VL: p = 0.027) and reduced trailing-limb activation at step contact (VM: p = 0.015; VL: p = 0.018), with sagittal-plane ankle differences (p = 0.004). During step-down, when the affected limb initiated ascent, trailing limb activation was higher at descent completion (VL: p < 0.001; VM: p = 0.003; BF: p = 0.009), with coronal-plane hip deviations (p < 0.001). When the contralateral limb-initiated ascent, trailing-limb muscles activation differences (VM: p < 0.001; VL: p = 0.015; BF: p = 0.007) and ankle/coronal-plane asymmetries (p ≤ 0.049) persisted. Conclusions: The StUD-F task elicits altered strategies in KOA, including elevated quadriceps–hamstring co-activation and altered sagittal/coronal alignment, and habitual limb choice across ascent and descent. These adaptations may enhance stability and joint protection but could increase medial compartment loading. The findings support rehabilitation focused on dynamic control, alignment, and shock absorption. Full article

Background/Objectives: Persistent strength deficits and psychological impairments may compromise return to sport (RTS) after anterior cruciate ligament reconstruction (ACLR). We investigate the relationship between thigh muscle isokinetic strength recovery at six months after ACLR and long-term psychological outcomes related to RTS in competitive male soccer players. Methods: Sixty male soccer players who underwent primary ACLR with bone–patellar tendon–bone autograft were retrospectively analyzed. Isokinetic testing of quadriceps and hamstrings was performed one week before surgery and six months post-surgery at 90°/s and 180°/s. Limb symmetry index (LSI) was calculated both pre- and post-operatively. At long-term follow-up (mean ≈ 4 years after RTS), athletes completed questionnaires assessing RTS status, ACL re-injuries, sport-related perceptions, and kinesiophobia using the Tampa Scale for Kinesiophobia (TSK). Statistical analyses were conducted to explore associations between post-operative LSI and TSK scores and to compare psychological and neuromuscular outcomes between athletes with and without ACL re-injury. Results: Absolute quadriceps and hamstring peak torque values significantly increased from pre- to post-surgery, with quadriceps strength deficits persisting only in the operated limb. However, quadriceps LSI significantly decreased post-operatively, while hamstring LSI remained stable. Pearson correlation analysis revealed a weak positive association between post-operative quadriceps LSI at 90°/s and TSK scores (r = 0.34). Overall, RTS rate was 91.7%, but a second ACL injury occurred in 18.2% of athletes. No significant differences were observed between re-injured and non-re-injured athletes in TSK scores or post-operative LSI values at either angular velocity (all p > 0.29). High kinesiophobia (TSK ≥ 37) was present in 56.7% of the cohort at long-term follow-up. Conclusions: Despite significant strength gains, quadriceps limb symmetry worsened six months after ACLR, with deficits confined to the operated limb, suggesting persistent neuromuscular inhibition. These physical deficits coexist with long-term kinesiophobia despite high RTS rates. The weak associations between strength symmetry and psychological outcomes highlight the multifactorial nature of RTS and support the need for an integrated physical, psychological, and neuro-cognitive approach to rehabilitation and RTS decision-making. Full article

Exoskeletons are increasingly used in industrial settings, yet most are designed for structured, repetitive tasks, limiting adaptability to dynamic movements. In construction, frequent locomotion tasks demand continuous lower-limb engagement, and ladder climbing places substantial loads on coordination and flexibility. This study aimed to identify key muscles involved in climbing to support the development of adaptive exoskeletons. Ten healthy male participants (33.8 ± 3.4 years; 178.7 ± 5.0 cm; 87.4 ± 16.1 kg) performed vertical and A-frame ladder ascents in a controlled laboratory setting. Surface electromyography was recorded from eight right-leg muscles and processed using band-pass filtering, rectification, and root mean square smoothing. Two normalization strategies were applied: walking normalization, expressing climbing activity relative to level walking, and maximum voluntary contraction normalization, with amplitudes expressed as a percentage of maximum voluntary contraction. Our results showed that all muscles were more active in climbing than walking, with quadriceps (vastus medialis, vastus lateralis, rectus femoris) exhibiting the greatest increases. Gastrocnemius also approached or exceeded 100%MVC, tibialis anterior averaged 70–80%MVC, and hamstrings contributed 20–40%MVC mainly for stabilization. Vertical and A-frame ladders followed similar patterns with subtle posture-related variations. These findings highlight knee extensors as primary targets for adaptive exoskeleton assistance during ladder climbing tasks commonly performed on construction sites. Full article

(1) Background: We developed a novel technology that regulates human locomotion using transcutaneous electrical spinal cord stimulation to activate spinal locomotor networks and posterior root stimulation to activate leg flexor and extensor motor pools during swing and stance phases, respectively. This technology effectively restores walking in post-stroke individuals while forward propulsion in the stance phase and foot dorsiflexion in the swing phase are insufficient. In this study the effectiveness of regulating the stance and swing phases while healthy volunteers walked on a treadmill with transcutaneous electrical stimulation of the posterior roots, leg muscles, and their combined effects has been examined. (2) Methods: We analyzed the kinematic characteristics of stepping movements in healthy participants with spinal stimulation of the posterior roots and flexor/extensor leg muscles. (3) Results: Our findings clearly show that posterior root stimulation at T12 combined with tibialis anterior muscle stimulation during the swing phase effectively regulates foot dorsiflexion, whereas posterior root stimulation at L2 combined with hamstrings and medial gastrocnemius stimulation during the stance phase effectively regulates forward propulsion. (4) Conclusions: Combined stimulation in the stance and swing phases within the same gait cycle resulted in the most coordinated stepping, and effective control of forward propulsion and foot dorsiflexion. Full article