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Barbell squats are commonly utilized in resistance training for rehabilitation, daily living enhancement, and improving sports performance. The current study investigated the kinematic and electromyographic (EMG) parameters in the squat between sexes across different repetition ranges (1-, 3-, 6-, and 10-RM) among recreationally strength-trained subjects. A total of 26 subjects (13 men: age 25 ± 3.5 years, height 178.2 ± 5.8 cm, weight 82.3 ± 9.1 kg; 13 women: age 24 ± 4.1 years, height 165.4 ± 6.3 cm, weight 68.2 ± 8.7 kg) participated in the study. The level of significance was set at p<0.05. The findings revealed no sex-specific differences in average barbell velocity across repetition ranges. However, the 1-RM showed a significantly lower average velocity compared to the final repetition of other repetition ranges (p<0.001), with the last repetition at 10-RM revealing a significantly higher velocity (p<0.001). Women had greater maximal angular hip extension velocity in the final repetitions of the 6- and 10-RM (p≤0.035, ηp2≤0.20), while both sexes displayed lower maximal angular knee extension velocity in the final repetition of the 10-RM (p = 0.028, ηp2 = 0.15). Moreover, men had lower EMG amplitude in the rectus femoris (3- and 10-RM), soleus, and lateral vastus (10-RM) compared to women (p≥0.011, ηp2≥0.26). It was concluded that 10-RM differed greatly in kinematics and EMG, suggesting different fatigue mechanisms compared to other repetition ranges with heavier loads. Furthermore, sex differences in EMG and angular hip extension velocity might imply sex-specific fatiguing mechanisms during high-repetition squats. These considerations could be important when prescribing training programs. [ABSTRACT FROM AUTHOR]

This study aimed to investigate the impact of a high barbell vs. low barbell placement on net joint moments, muscle forces, and muscle-specific moments in the lower extremity joints and muscles during maximum back squats. Twelve recreationally trained men (age 5 25.3 6 2.9 years, height 5 1.79 6 7.7 m, and body mass 5 82.8 6 6.9 kg) volunteered for the study. A marker-based motion capture system and force plate data were used to calculate the net joint moments, and individual muscle forces were estimated using static optimization. Muscle forces were multiplied by their corresponding internal moment arms to determine muscle-specific moments. Statistical parametric mapping was used to analyze the effect of barbell placement as time-series data during the concentric phase. The 3 repetition maximum barbell load lifted by the subjects was 129.1 6 13.4 kg and 130.2 6 12.7 kg in the high bar and low bar, which were not significantly different from each other. Moreover, no significant differences were observed in net joint moments, muscle forces, or muscle-specific moments for the hip, knee, or ankle joint between the low- and high bar placements. The findings of this study suggest that barbell placement plays a minor role in lower extremity muscle forces and moment-specific moments when stance width is standardized, and barbell load lifted does not differ between barbell placements among recreationally resistance-trained men during maximal back squats. Therefore, the choice of barbell placement should be based on individual preference and comfort. [ABSTRACT FROM AUTHOR]

This study's objective was to investigate the impact of a 10-week in season contrast rubber band training program on athletic performance in young female handball players. Youth athletes (15.8 ± 0.2 years) were randomly assigned to an intervention (n = 16) or a control group (n = 14). The intervention group performed contrast rubber band training (20 sessions over two weeks), while the control group maintained regular in-season training. The modified T-test, squat jump, countermovement jump, standing long jump, repeated sprint ability, 1-RM bench press and half squat, along with upper and lower limb force-velocity tests were performed. The intervention group experienced significantly larger performance enhancements than the control group in the modified T-test [p < 0.001; d = 1.45 %Δ (intervention = −7.1, control = −0.8)], vertical jump [p ≤ 0.009; d ≥ 0.72; %Δ (8.4 < intervention < 19.8, 4.1 < control < 12.2)], 1-RM strength [p ≤ 0.04, d ≥ 0.80; %Δ (37.1 < intervention < 39.7, 7.2 < control < 11.2)], all force-velocity scores for the upper limbs [p ≤ 0.009; d ≥ 0.72; %Δ (21 < intervention < 82, 0.1 < control < 11.6)], three of four force-velocity scores for the lower limb performance [p ≤ 0.02; d ≥ 0.64; %Δ (6.4 < intervention < 31.3, 0.8 < control < 11.1)] and all repeated sprint times [p < 0.001; d ≥ 1.15; %Δ (−3.4 < intervention < −3.1, −1.9 < control < −0.5)]. It was concluded that ten weeks of contrast rubber band training positively affected most motor abilities in youth female handball athletes. Therefore, coaches and practitioners should consider utilizing contrast rubber band strength training as a time and resource-efficient means of improving physical fitness of youth handball players. [ABSTRACT FROM AUTHOR]

Purpose: To compare the effects of increased load of low- versus high-intensity endurance training on performance and physiological adaptations in well-trained endurance athletes. Methods: Following an 8-week preintervention period, 51 (36 men and 15 women) junior cross-country skiers and biathletes were randomly allocated into a low-intensity (LIG, n = 26) or high-intensity training group (HIG, n = 25) for an 8-week intervention period, load balanced using the overall training impulse score. Both groups performed an uphill running time trial and were assessed for laboratory performance and physiological profiling in treadmill running and roller-ski skating preintervention and postintervention. Results: Preintervention to postintervention changes in running time trial did not differ between groups (P =.44), with significant improvements in HIG (−2.3% [3.2%], P =.01) but not in LIG (−1.5% [2.9%], P =.20). There were no differences between groups in peak speed changes when incremental running and roller-ski skating to exhaustion (P =.30 and P =.20, respectively), with both modes being significantly improved in HIG (2.2% [3.1%] and 2.5% [3.4%], both P <.01) and in roller-ski skating for LIG (1.5% [2.4%], P <.01). There was a between-group difference in running maximal oxygen uptake changes (P =.04), tending to improve in HIG (3.0% [6.4%], P =.09) but not in LIG (−0.7% [4.6%], P =.25). Changes in roller-ski skating peak oxygen uptake differed between groups (P =.02), with significant improvements in HIG (3.6% [5.4%], P =.01) but not in LIG (−0.1% [0.17%], P =.62). Conclusion: There was no significant difference in performance adaptations between increased load of low- versus high-intensity training in well-trained endurance athletes, although both methods improved performance. However, increased load of high-intensity training elicited better maximal oxygen uptake adaptations compared to increased load of low-intensity training. [ABSTRACT FROM AUTHOR]

Producing comparable/greater ground reaction forces (GRFs) at faster running speeds is beneficial for sprint performance, and assisted sprint training is used to induce faster running speed conditions. This study aimed to demonstrate the characteristics of assisted sprinting at the maximal speed phase and investigate acute differences to control sprinting. Fifteen sprinters completed control and assisted (5 kg) sprints over force platforms. Assisted sprinting increased running speed (9.3% mean difference), while propulsive mean force (−4.3%) and impulse (−12.4%) decreased, suggesting that running speed improvements were caused primarily by assisted pulling force rather than improvements in anteroposterior force production of athletes. In addition, vertical mean force increased (4.2%), probably due to braking mean force (34.2%) and impulse (32.5%) increases. Magnitude of control trial maximum speed was achieved earlier (during acceleration) in assisted trials, and net anteroposterior (includes both braking and propulsive components) mean force (67.2%) and impulse (67.9%) increased at this matched speed, suggesting that assisted sprints could be used to practice producing greater GRFs at comparable speeds. Running speed improvement by pulling force was associated with contact time decreases (r = -.565), suggesting that shortening contact time may be important for effective assisted sprinting. [ABSTRACT FROM AUTHOR]

Purpose: To compare the assessment of the maximal oxygen consumption (VO2max) in a traditional graded exercise test (GXT) with a 1-km self-paced running test on a nonmotorized treadmill in men and women. Methods: A total of 24 sport-science students (12 women: age 23.7 [7.7] y, body height 1.68 [0.02] m, body mass 66.6 [4.3] kg; 12 men: 22.1 [3.1] y, body height 1.82 [0.06] m, body mass 75.6 [11.0] kg) performed a traditional GXT on a motorized treadmill and a 1-km self-paced running test on a nonmotorized treadmill. VO2max, blood lactate, heart rate, and rating of perceived exertion, together with running velocity and duration at each test, were measured. Results: The main findings of the study were that the 1-km test produced significantly higher VO2max values (53.2 [9.9] vs 51.8 [8.8] mL/kg/min) and blood lactate concentrations (11.9 [1.8] vs 11.1 [2.2] mmol/L) than the GXT (F ≥ 4.8, P ≤.04, η2 ≥.18). However, after controlling for sex, these differences were only present in men (60.6 [8.1] vs 58.1 [8.0] mL/kg/min , P =.027). Peak running velocity was higher in the GXT than in the 1-km test (15.7 [2.7] vs 13.0 [2.8] km/h). Men had higher VO2max values and running velocities than women in both tests. However, men and women used approximately similar pacing strategies during the 1-km test. Conclusions: Higher VO2max values were observed in a 1-km self-paced test than in the GXT. This indicates that a 1-km running test performed on a nonmotorized treadmill could serve as a simple and sport-specific alternative for the assessment of VO2max. [ABSTRACT FROM AUTHOR]

Purpose: To compare the effects of a short specific and a long traditional warm-up on time-trial performance in cross-country skiing sprint using the skating style, as well as related differences in pacing strategy and physiological responses. Methods: In total, 14 (8 men and 6 women) national-level Norwegian cross-country skiers (age 20.4 [3.1] y; VO2max 65.9 [5.7] mL/kg/min) performed 2 types of warm-up (short, 8 × 100 m with gradual increase from 60% to 95% of maximal speed with a 1-min rest between sprints, and long, ∼35 min at low intensity, including 5 min at moderate and 3 min at high intensity) in a randomized order with 1 hour and 40 minutes of rest between tests. Each warm-up was followed by a 1.3-km sprint time trial, with continuous measurements of speed and heart rate. Results: No difference in total time for the time trial between the short and long warm-ups (199 [17] vs 200 [16] s; P =.952), or average speed and heart rate for the total course, or in the 6 terrain sections (all P <.41, η2 <.06) was found. There was an effect of order, with total time-trial time being shorter during test 2 than test 1 (197 [16] vs 202 [16] s; P =.004). No significant difference in blood lactate and rating of perceived exertion was found between the short versus long warm-ups or between test 1 and test 2 at any of the measurement points during the test day (P <.58, η2 >.01). Conclusions: This study indicates that a short specific warm-up could be as effective as a long traditional warm-up during a sprint time trial in cross-country skiing. [ABSTRACT FROM AUTHOR]

When performing the traditional barbell back squat, athletes may experience discomfort in the shoulders or be limited by shoulder mobility. The Squatbar® is a barbell designed to be ergonomic to the shoulders but has never, in the scientific literature, been compared to the traditional Olympic barbell. Thus, the current study investigated kinematics, kinetics, and myoelectric activity (EMG) between the Squatbar® barbell and the Olympic barbell when performing a one-repetition maximum (1-RM) back squat. Twelve strength-trained men (body mass: 83.5 ± 7.8 kg, age: 27.3 ± 3.8 years, height: 180.3 ± 6.7 cm) performed a 1-RM squat with both the Olympic and Squatbar® barbells. The paired samples t-test revealed significantly more weight was lifted with the Olympic barbell compared to the Squatbar® barbell (148 ± 21 kg vs. 144.5 ± 20 kg) and was accompanied by greater shoulder external rotation (74 ± 7.5° vs. 59.6 ± 9.2°). No differences in joint kinematics of the lower limbs, kinetics, or EMG were observed between the two barbells. The results of the current study indicate the Squatbar® to be a suitable substitution for the Olympic barbell for athletes with reduced shoulder mobility when performing the squat. It was concluded that the Squatbar® induces similar kinetics, kinematics, and EMG when compared to the Olympic barbell, except for reducing external rotation of the shoulder. [ABSTRACT FROM AUTHOR]