We aimed to investigate the impact of isolated static stretching (4 sets of 30 seconds) and its combined form with 10 repetitive drop jumps on lower limb performance during squat jumps at different knee joint starting angles (60°, 90°, and 120°). Thirteen participants completed three randomly ordered experimental visits, each including a standardized warm-up and squat jumps at three angles, apart from the intervention or control. Information was gathered through a three-dimensional movement tracking system, electromyography system, and force platform. The electromyography data underwent wavelet analysis to compute the energy values across the four wavelet frequency bands. The average power (Pavg), peak power (Ppeak), peak ground reaction force (GRFpeak), peak center of mass velocity (Vpeak), and force-velocity relationship at peak power (SFv) were extracted from the force and velocity-time data. The results revealed no significant influence of isolated static stretching, or its combined form with drop jumps, on the energy values across the frequency bands of the gastrocnemius, biceps femoris and rectus femoris, or the Pavg or Ppeak (P > 0.05). However, at 120°, static stretching reduced the GRFpeak (P = 0.001, d = 0.86) and SFv (P < 0.001, d = 1.12), and increased the Vpeak (P = 0.001, d = 0.5). The GRFpeak, Pavg, Ppeak, and SFv increased with an increase in the joint angle (P < 0.05), whereas the Vpeak decreased (P < 0.05). These findings suggest that static stretching does not diminish power output during squat jumps at the three angles; however, it alters GRFpeak, Vpeak, and the relative contributions of force and velocity to peak power at 120°, which can be eliminated by post-activation performance enhancement. Moreover, compared to 60° and 90°, 120° was more favorable for power and peak force output.

In general, at the same level of exercise, female athletes are three to six times more likely to injure an anterior cruciate ligament (ACL) than male athletes. Female athletes also had higher rates of ACL injury than males in a single-leg landing task after a backcourt backhand side overhead stroke in badminton. In many previous studies, stiffness of the musculoskeletal system in the lower limbs has been reported as a potential factor contributing to differences in ACL injury rates between genders. The purpose of this study was to describe the differences between genders in leg and knee stiffness in male and female athletes during a single-leg landing action after the backhand side overhead shot in the backcourt. Eight male athletes and eight female athletes participated in this test. Leg stiffness and knee stiffness were calculated separately for male and female athletes during the landing phase. The results showed that both absolute and normalized leg stiffness were lower in female athletes than in male athletes (p < 0.05). And both absolute and normalized knee stiffness were also lower than male athletes (p < 0.05). The low leg stiffness and knee stiffness demonstrated by females in this single-leg drop task compared to male athletes may indicate that females have lower dynamic leg stability than males during the drop, which may lead to hypermobility of the knee joint and may put females at a higher risk of injury in this high-risk maneuver for non-contact cruciate ligament injuries.

Purpose: This study evaluated how lower-limb explosive strength relates to 15-m speed-climbing performance by combining jump kinetics, muscle morphology, and surface electromyography (sEMG). Methods: Fifteen Chinese speed climbers (10 men, 5 women) who had placed within the top 3–6 at national-level competitions underwent ultrasound imaging of the rectus femoris (RF) and medial gastrocnemius (GM), and then, in random order, completed unilateral and bilateral squat jumps, countermovement jumps, and a 15-m speed-climbing test. Force plate recorded peak force ( F _peak ) and rate of force development (RFD); sEMG yielded integrated EMG for the main lower-limb muscles. Results: Unilateral and bilateral squat jumps/countermovement jumps F _peak correlated with climbing speed ( r = .63–.77, P = .004–.029). Both right-leg ( r = .62, P = .033) and bilateral ( r = .62, P = .03) countermovement jumps RFD correlated with speed. Bilateral-jump F _peak correlated with right-side RF thickness ( r = .59–.81, P = .001–.043), whereas bilateral RFD with both GM thickness and fascicle length ( r = .58–.63, P = .029–.049). During climbing, speed negatively correlated with left-side RF integrated EMG ( r = –.6, P = .041) and positively with bilateral GM integrated EMG ( r = .59–.64, P = .026–.045; other muscles P > .05). Conclusions: Right-leg RF thickness appears to drive F _peak , and thus climbing speed, whereas GM thickness and fascicle length primarily influence RFD. A contrasting activation pattern (lower RF, higher GM engagement) likely underlies these morphology–performance links. Coaches can target maximal-strength and plyometric training to enlarge the right RF and GM and lengthen GM fascicles, potentially improving speed-climbing performance.

This study aimed to explore the impact of playing experience on vertical release velocity (VV) and horizontal release velocity (HV) during mid- and long-distance jump shots, and the relationships among VV, HV, and the contraction intensity levels of primary muscles. The study utilized a cross-sectional experimental design, with 30 participants completing three effective jump shots at distances of 4.8 m and 6.75 m. Data were collected using a 3D motion capture system and an electromyography (EMG) recording system, with velocity-time data extracted to determine VV and HV, and EMG data analyzed using wavelet analysis. A two-factor mixed ANOVA was used to compare differences in VV and HV under different conditions, and Spearman correlation analysis was employed to explore relationships among VV, HV, and the energy values of major muscle frequency bands. The results indicated that playing experience significantly improved VV (p < 0.001). At mid-range distances, experienced athletes' VV positively correlated with the low frequency band (r = 0.479, p = 0.048) and near frequency band (r = 0.539, p = 0.038) energy values of the triceps brachii (TB), as well as the high frequency band (r = 0.679, p = 0.005) and mid-high frequency band (r = 0.571, p = 0.026) energy values of the anterior deltoid (AD). At long-range distances, VV negatively correlated with the low frequency band energy values of the flexor carpi radialis (r = −0.5, p = 0.045), the high frequency band of TB (r = −0.564, p = 0.028), and the near frequency band of AD (r = −0.496, p = 0.046). These findings suggest that playing experience significantly alters VV during jump shots, and this alteration may be associated with the overall activity of the TB, the explosive activity of the AD, and the baseline activity of the rectus femoris.

Purpose: This study investigated lower-limb asymmetry in speed climbers and its relationship with climbing time while exploring the underlying mechanisms through muscle-thickness and activation. Methods: Nineteen speed climbers completed muscle-thickness measurements, single-leg countermovement-jump tests, and speed-climbing tests. Muscle thickness was assessed using ultrasound, single-leg countermovement-jump tests were performed on a force platform, and climbing tests were conducted on a standardized climbing wall. Data were used to calculate muscle thickness, peak force (F_peak), rate of force development, and integrated electromyography [EMG] percentage (iEMG %). Correlation analysis assessed the relationship between lower-limb asymmetry and climbing time, while paired t tests and asymmetry indices were used to analyze differences and asymmetry levels. Results: Results showed significant positive correlations between climbing time and asymmetry indices of F_peak (r = .57, P = .028) and rate of force development (r = .52, P = .045). No significant differences were observed in F_peak, rate of force development, muscle thickness, iEMG (%) during jumping, or iEMG (%) of the biceps brachii and medial gastrocnemius during climbing (P > .05). However, significant differences were found in rectus femoris iEMG (%) during climbing (P = .028, d = 0.89). Most asymmetry indices, except for F_peak, muscle thickness, and iEMG (%) of the biceps brachii and medial gastrocnemius, exceeded 15%, indicating high asymmetry levels. Conclusions: This study highlights significant lower-limb asymmetry in speed climbers, potentially affecting performance. Findings suggest neural-activation differences, rather than muscle thickness, as the primary contributors. Regular monitoring and targeted interventions are recommended to reduce asymmetry and its impact on performance.

Purpose: This study investigated how playing experience influences joint kinetics and ball-release velocity during mid- and long-range jump shots. Wrist, elbow, shoulder and knee rate of torque development (RTD), peak power (P _peak ), and angular impulse (AI) were quantified, along with vertical release velocity (VV) and horizontal release velocity (HV) at release. Methods: In a cross-sectional design, 15 experienced and 15 novice male collegiate basketball players each performed three made jump shots from 4.8 m and 6.75 m. A 3-D motion-capture system synchronised with force plates provided the data used to compute RTD, P _peak , AI, VV and HV. Outcomes were compared with a two-way mixed ANOVA. Results: Experienced players exhibited greater wrist AI ( p < 0.001), elbow RTD ( p = 0.002), P _peak ( p = 0.045) and AI ( p < 0.001), knee P _peak ( p = 0.002) and VV ( p < 0.001). Longer shooting distance increased shoulder P _peak ( p = 0.036) and HV ( p = 0.018). Conclusions: Collectively, these results show that experience enhances joint kinetic output, providing the mechanical foundation for more efficient and dependable shooting. For novice players, emphasising wrist-endurance work, explosive-power training for the elbow and knee, and targeted drills to raise VV is recommended to improve overall on-court shooting performance.