International journal of sports medicine最新文献

The aim of this study was twofold: (1) to make a sex comparison on dryland strength, range of motion (ROM), and kinematics of the breaststroke underwater pullout and (2) to analyze the relationship between dryland strength, ROM, and kinematics of different pullout techniques in both male and female swimmers. Sixteen trained swimmers, nine males (20.67±2.71 years old) and seven females (18.86±0.83 years old), performed 3×25 m breaststroke using two pullout breaststroke techniques: Fly-Kick first and Combined. A speedometer and video footage were used to assess the pullout phase kinematics and the total underwater sequence. Dryland assessments included the maximum jump height, the isometric peak strength of internal shoulder rotation (IR) (at 90°), and knee extensors (at 60°). The joint ROM of knee flexion (KF), plantar flexion (PF), and hip internal rotation were also considered. Velocity-time curves of both techniques according to sex were dissected using statistical parametric mapping. An independent t-test was used to compare differences between swimmers' sex in kinematic and dryland variables while the Pearson correlation coefficient (r) was used for associations. Higher instantaneous velocity at ~24-26, ~31-42, and 54.5-63% during the glide phase duration was found for males in the Fly-Kick first technique. Males also displayed a higher peak (3.29 m·s^-1) and mean velocity (1.58-1.65 m·s^-1) in the total underwater path or in the glide and propulsion phases of both pullout techniques. While males performed better in jump height (33.89 cm) and peak strength of IR (172-176 N), females showed a higher ROM mostly in PF (161-165°). A high and positive correlation between dryland strength and kinematics in both pullout techniques was found in males. The ROM failed to correlate with pullout kinematics, except for the KF in females during the recovery phase (r=0.82-0.86). In conclusion, male breaststrokers perform better than females on dryland strength but not in joint ROM, which provides them with an advantage mainly in the Fly-Kick first underwater pullout.

Acute adaptations to fatiguing conditions may be altered concerning the training background. Muscle activation and coordination are affected by fatigue, although differences between subjects with different training status remain unclear. This study evaluated 28 individuals, investigating differences between strength-trained and untrained individuals in leg-press isometric maximum voluntary contractions before and after a back-squat fatiguing protocol. The peak force, rate of force development, electromyographic amplitude of seven lower-limb muscles, rate of electromyographic rise of agonist muscles and intermuscular coherence between synergist or antagonist pairs of muscles were evaluated. Strength-trained individuals exhibited a greater peak force, maximal rate of force development and rate of force development at 150-200 ms. All force-related variables decreased with fatigue in both groups, and the peak force decreased to a greater extent in strength-trained individuals. The electromyographic amplitudes of the vastus medialis (p=0.005) and rectus femoris (p=0.039) increased in both groups, and the rate of electromyographic rise of the rectus femoris increased in strength-trained individuals but decreased in untrained individuals (time x group interactions: 0.006<p<0.025). Additionally, coherence analysis revealed greater coherence in the 15-35 Hz band between the rectus femoris and the vastus medialis in untrained individuals than in strength-trained individuals, while fatigue affected coherence across the bands of interest differently concerning the functional relationship between the paired muscles. Different training status imply different acute responses to fatigue relying on changes in the activation of agonist muscles as well as coordination between the pairs of synergist and/or antagonist muscles.

This study aimed to investigate the effects of an anterior superficial myofascial chain strengthening program on maximum ball speed, myofascial elasticity, muscle activation, and shank kinematics in young soccer players. A total of 32 licensed soccer players, aged 13-14 years, were recruited and randomly assigned to either an exercise group or a control group. Participants in the exercise group underwent an 8-week anterior superficial myofascial chain strengthening program consisting of three progressive phases. At baseline and after the 8-week intervention, the maximum ball speed during the instep kick was measured using a radar gun; muscle activation was assessed via surface electromyography; and shank rotational velocity and acceleration were recorded using an inertial measurement unit. Myofascial elasticity was evaluated using a myotonometer. Compared to the control group, the exercise group demonstrated significant improvements in the maximum ball speed, muscle activation, and myofascial elasticity. However, no significant changes were observed in shank rotational velocities or accelerations. Correlation analysis revealed that changes in maximum ball speed were significantly associated with alterations in muscle activation and myofascial elasticity. The ASMC strengthening program increases the maximum ball velocity during the instep kick in young soccer players by improving muscle activation and myofascial elasticity.

This study aimed to develop predictive equations for unilateral (1-leg) half-squat exercise loads that would elicit equivalent neuromuscular activation, velocity, and force outputs as bilateral (2-leg) half-squat exercise loads. Twelve male soccer players (age 22.9±1.8 y, stature 1.8±0.1 m, and body mass 76.5±6.2 kg) performed both 1-leg and 2-leg half-squats using a Smith-machine. Surface electromyography of vastus lateralis and vastus medialis, barbell velocity and force outputs were measured across incremental loads. Linear regression analyses were conducted to develop predictive equations for 1-leg loads that would match 2-leg exercise outcomes. Three predictive equations were developed: (1) Equivalent muscle activation: 1-leg external load=50% of 2-leg external load -2 kg (r=0.923-0.997, p<0.05). (2) Equivalent barbell velocity: 1-leg external-load=71% of 2-leg external load -17.6 kg (r= -0.916 to 0.994, p<0.05). (3) Equivalent force-output: 1-leg external load=41% of 2-leg external load - 28 kg (r=0.937-0.998, p<0.05). This preliminary investigation provides initial predictive equations for equating unilateral and bilateral half-squat exercises, though validation on independent populations remains necessary. These tools enable practitioners to estimate equivalent loads between exercise modalities using a single one-repetition maximum assessment, facilitating targeted training and rehabilitation program development through accurate load prescription and performance comparisons. Further research is needed to validate these equations on large population and in different sports.

Caffeine is a well-established ergogenic aid with a wealth of evidence demonstrating beneficial effects for physical performance, cognitive function and sport-specific skills. Intuitively, it may be considered that such effects may translate to improved soccer specific performance, however, evidence examining the effects of caffeine on the interacting demands of soccer match play is sparse. Given that caffeine supplementation is highly prevalent in professional soccer, and in a number of cases practices adopted lack supporting evidence, this review evaluates the current state of the knowledge regarding the ergogenic potential of acute caffeine consumption specifically for soccer performance. Furthermore, this review identifies knowledge gaps to guide future research, and whilst considering the unique environmental constraints, uses the available evidence to develop practical guidelines for safe and effective use.

We investigated the effects of plyometric and isometric warm-up exercises on handball throwing velocity and verified the relationships between strength measures and throwing velocity. Sixteen U-22 elite male handball players (age: 19.8±0.9 y and handball training experience: 10.5±1.0 y) of the Spanish University Championship-winning team participated in this study. Players were assessed for maximum isometric shoulder internal rotation strength (kg), and the loads (kg) associated with 1 m/s in half squat and bench press exercises. Subsequently, they performed a standardized warm-up plus isometric vs. plyometric vs. control exercises in a randomized order followed by the evaluation of ball throwing velocity. There were no significant differences in throwing velocity following any condition. Moderate significant correlations were observed between throwing velocity and the load associated with 1 m/s in the half squat under all conditions (r=0.56-0.61 and p<0.05) and in the bench press after plyometric (r=0.50 and p=0.047). The control condition which included submaximal running resulted in similar throwing velocity to the experimental conditions including strength exercises. The identified associations between the loads associated with 1 m/s in the half squat and bench press exercises highlighted the important role of muscle power in handball players' throwing ability.

Fastpitch softball is popular among adolescent and collegiate female athletes. Softball pitchers are susceptible to overuse injuries, and clinical and performance outcome measures can be used to evaluate injury risk and readiness to return to play. Our purpose was to examine clinical and performance-related outcome measures in pitchers using a systematic review of the softball literature published since 1990. PubMed, Embase, CINAHL, and SPORTDiscus databases were searched using the term "softball" AND "pitching" OR "injuries". Inclusion criteria were studies reporting clinical or performance outcomes like strength, range of motion, anthropometrics, and patient-reported measures. A preliminary screening of studies was completed based on abstracts. Full-text articles were reviewed by two reviewers. Thirty-seven studies met all inclusion criteria. The risk of bias was low for all included studies. Studies reporting body composition (n = 4), range of motion (n = 10), strength (n=12), functional testing (n=4), and patient-reported outcomes (n=3) were included in data extraction. There was a high degree of variability in outcome measures used to evaluate softball pitchers. Ten case studies were included in the discussion of results. Researchers would benefit from a standardized list and protocol for clinical and performance outcome measures used for softball pitchers. This systematic review identifies important gaps in the literature.

Accurate measurement of training intensity is crucial for optimizing endurance running performance. Lactate threshold heart rate and lactate threshold speed are commonly used but require invasive, costly methods. Heart rate variability metrics offer a non-invasive alternative by assessing autonomic nervous system activity. This study evaluated the validity of various heart rate variability metrics in predicting the lactate threshold heart rate and lactate threshold speed during indoor and outdoor graded exercise tests in 19 recreational runners. Heart rate variability thresholds were determined using SD1, SD2, detrended fluctuation analysis scaling exponent for short-term fluctuations, detrended fluctuation analysis scaling exponent for long-term fluctuations, standard deviation of NN intervals, and root mean square of successive RR intervals via the Dmax method, and are referred to as HRVT₁ to HRVT₆. Indoor graded exercise test results showed that heart rate at heart rate variability threshold often underestimated the lactate threshold heart rate, with all heart rate variability thresholds, except speed at heart rate variability threshold (detrended fluctuation analysis scaling exponent for long-term fluctuations, p=0.06), showing significant differences from lactate threshold. Moderate correlations were observed for HRVT_5HR (standard deviation of NN intervals, r=0.66), HRVT_2speed (SD2, r=0.56), and HRVT_3speed (detrended fluctuation analysis scaling exponent for short-term fluctuations, r=0.70). Outdoor graded exercise tests showed no significant differences between most heart rate variability thresholds and lactate threshold, except HRVT_6HR (root mean square of successive RR intervals, p=0.03). Speed at heart rate variability threshold demonstrated moderate correlations (r=0.54-0.7) with the lactate threshold speed. While the heart rate variability threshold and lactate threshold may reflect different physiological thresholds, heart rate variability thresholds, particularly those based on detrended fluctuation analysis scaling exponent for long-term fluctuations, showed promise as non-invasive predictors of lactate threshold in recreational runners.

Aging impairs cardiovascular, autonomic and immune responses. Whether the resistance training influences such responses is unknown. We tested the hypothesis that resistance training could attenuate such impairments in older adults. Sixty-eight older adults were randomized into a control group (n=38) and a training group (n=31). Resistance training sessions were conducted three times per week, 12-week period, at a moderate intensity (65%-80% of 1 RM). Cardiovascular hemodynamics were evaluated by impedance cardiography (PhysioFlow), electrocardiogram including autonomic imbalance, a 1 minute sit-to-stand test including partial oxygen saturation (SpO₂) monitoring, maximal expiratory pressure, maximal inspiratory pressure, whole blood analysis and pro- and anti-inflammatory cytokines in plasma. After 12 weeks of resistance training, an improvement in stroke volume (p<0.0092), cardiac output (p<0.0235), systemic vascular resistance (p<0.0424), end diastolic volume (p<0.0053), early diastolic function (p<0.0398), pNN50 (p<0.0485), and the TRI (p<0.0029) was observed when comparing pre- versus post-intervention in the resistance training group. Resistance training also improved maximal expiratory pressure (p<0.0036) and maximal inspiratory pressure (p<0.0034). Functional capacity in the 1- minute sit-to-stand test (p<0.0004) and oxygen desaturation (p<0.0008) were improved in the resistance training group. In addition, resistance training decreased serum levels of pro-inflammatory cytokines, interleukin-6 (p<0.0001) and tumor necrosis factor alpha (p<0.043), and increased anti-inflammatory cytokines, interleukin-10 (p<0.0003) and protein klotho (p<0.0001). Resistance training improves cardiovascular hemodynamics, autonomic imbalance and immune response in older adults, while the control group did not show any evolution.

The aim of this study was to evaluate the predictive capacity of functional electromechanical dynamometry for sprint canoe performance. Twenty-one world-class sprint canoeists underwent two functional electromechanical dynamometry assessments (isometric and incremental load) in the sprint canoe-specific kneeling position. Race performance was assessed via official C1 500-m race times. Significant negative correlations were observed between 500-m race times and both the mean force (r=-0.72; p=0.001) and the peak force (r=-0.71; p=0.001) measured through the isometric dynamometric test. In the incremental test, a strong negative correlation was found between the race time and the number of strokes (Nreps; r=-0.85; p=0.001), as well as the absolute peak force (r=-0.80; p=0.001). These relationships remained significant when force values were adjusted for body mass. The strongest predictive model (R² _a=0.73) included the number of strokes from the incremental load test (C1 500-m race time=170.30-3.29 Nreps). These findings support the use of functional electromechanical dynamometry as a valid and sport-specific tool for assessing neuromuscular performance in elite sprint canoeists.