P between measures of unilateral and bilateral jumping performance and 10- and 25-m sprint performance. Fifteen division I women soccer players (height 165 ± 2.44 cm, mass 61.65 ± 7.7 kg, age 20.19 ± 0.91 years) volunteered to participate in this study. The subjects completed a 10- and 25-m sprint test. The following jump kinematic variables were measured using accelerometry: sprint time, step length, step frequency, jump height and distance, contact time, concentric contact time, and flight time (Inform Sport Training Systems, Victoria, BC, Canada). The following jumps were completed in random order: bilateral countermovement vertical jump, bilateral countermovement horizontal jump, bilateral 40-cm drop vertical jump, bilateral 40-cm drop horizontal jump, unilateral countermovement vertical jump (UCV), unilateral countermovement horizontal jump, unilateral 20-cm drop vertical jump (UDV), and unilateral 20-cm drop horizontal jump (UDH). The trial with the best jump height or distance, reactive strength (jump height or distance/total contact time), and flight time to concentric contact time ratio (FT/CCT) was recorded to analyze the relationship between jump kinematics and sprint performance. None of the bilateral jump kinematics significantly correlated with 10- and 25-m sprint time, step length, or step frequency. Right-leg jump height (r = −0.71, p = 0.006, SEE = 0.152 seconds), FT/CCT (r = −0.58, p = 0.04, SEE = 0.176 seconds), and combined right and left-leg jump height (r = −0.61) were significantly correlated with the 25-m sprint time during the UCV. Right-leg FT/CCT was also significantly related to 25-m step length (r = 0.68, p = 0.03, SEE = 0.06 m) during the UDV. The combined right and left leg jump distance to standing height ratio during the UDH significantly correlated (r = −0.58) with 10-m sprint time. In comparison to bilateral jumps, unilateral jumps produced a stronger relationship with sprint performance....

McCurdy, K, Walker, J, and Yuen, D. Gluteus maximus and hamstring activation during selected weight-bearing resistance exercises.J Strength Cond Res32(3): 594–601, 2018—The purpose of this study was to compare the gluteus maximus (GM) and hamstring group (HG) electromyographic (EMG) activation levels among selected weight-bearing resistance exercises. Eighteen young adult females with previous resistance training experience completed the study. Strength was assessed on the bilateral squat (BS) (3 repetition maximum [RM]), modified single-leg squat (MSLS) (3RM), and stiff-leg deadlift (SLDL) (8RM) to determine an 8RM load for all lifts. Surface EMG was collected after 48 hours of rest using wireless Trigno IM Sensors using EMMA software (Delsys), which also collected and synchronized 3D hip and knee motion. A maximum voluntary isometric contraction was determined for the GM and HG to normalize the EMG data. During EMG data collection, 3 repetitions were completed using an 8RM load on all 3 exercises. Gluteus maximus EMG was significantly greater than HG EMG on the BS (40.3 vs. 24.4%,p< 0.001), MSLS (65.6 vs. 40.1 %,p< 0.012), and SLDL (40.5 vs. 29.9 %,p< 0.047). The MSLS produced significantly greater HG EMG (p= 0.001) compared with the SLDL, whereas the SLDL was significantly greater (p= 0.004) than the BS. The MSLS GM EMG was also significantly greater (p< 0.001) than the SLDL and BS, whereas no difference was found between the SLDL and BS. Comparing the activation of the 2 muscle groups in all exercises, the GM seems to be the primary muscle recruited whereas the MSLS seems to produce greater GM and HG activation. The data indicate that it would be most beneficial to include the MSLS during GM and HG training.

McCurdy, K, Walker, J, Saxe, J, and Woods, J. The effect of short-term resistance training on hip and knee kinematics during vertical drop jumps. J Strength Cond Res 26(5): 1257–1264, 2012—The purpose of this study was to determine the effect of a weight-bearing free weight resistance training program alone on knee flexion, hip flexion, and knee valgus during unilateral and bilateral drop jump tasks. Twenty-nine young adult females with previous athletic experience were randomly divided into a control (n = 16) and a resistance training (n = 13) groups. The resistance training group completed 8 weeks of lower extremity, weight-bearing exercises using free weights, whereas the control group did not train. A pre- and posttest was conducted to measure knee valgus, knee flexion, and hip flexion during unilateral (30 cm) and bilateral (60 cm) vertical drop jumps for maximum height. Joint angles were determined using 3-dimensional electromagnetic tracking sensors (MotionMonitor; Innovative Sports Training, Inc., Chicago, IL, USA). Initial training intensity for the bilateral squat was 50% of the subject's 1 repetition maximum (RM), which increased 5% each week to 85% during the final week. Sets and repetitions ranged from 2 to 4 and from 4 to 12, respectively. The training loads for all other exercises (lunge, step-up, unilateral squat, and Romanian deadlift) increased from 15RM to 6RM from the initial to the final week. A repeated measures analysis of variance was used to determine differences in the hip and knee joint angles. No significant differences for knee valgus and hip flexion measures were found between the groups after training; however, knee flexion angle significantly increased in the training group from the pretest (77.2 ± 4.1°) to posttest (83.2 ± 3.7°) during the bilateral drop jump. No significant changes occurred during the unilateral drop jump. Bilateral measures for knee flexion, hip flexion, and knee valgus were significantly (p < 0.05) greater than the unilateral measures during the drop jump task, which indicate an increased risk for anterior cruciate ligament (ACL) injury during unilateral drop jumps. The data support that the strength and conditioning specialist can implement resistance training alone during a short-term training period to reduce the risk of ACL injury by increasing knee flexion during a bilateral drop jump task. Increased knee flexion angles after resistance training may indicate a reduced risk for knee injury from improved neuromuscular control, resulting in a softer landing.

The purposes of this study were to determine the validity and test-retest reliability of the 1 repetition maximum (1RM) chain-loaded, free-weight bench press (CBP) and to examine possible learning effects that may occur between the test-retest measurements. Nine resistance-trained men (20.58 +/- 1.31 years, 188.24 +/- 9.29 cm, 92.07 +/- 16.94 kg) and seven resistance-trained women (20.42 +/- 0.98 years, 175.61 +/- 9.32 cm, 73.61 +/- 10.80 kg) participating in Division II college basketball completed this study. Two familiarization sessions took place using light to moderate loads to learn proper technique. The subjects completed a 1RM test on the traditional plate-loaded bench press 4 days before completion of the CBP 1RM, which was followed by 4 days of rest before completing the retest. Intraclass correlation coefficients (ICC) and the percent coefficients of variation (CV) were used to determine relative and absolute test-retest reliability. Concurrent validity was determined from the Pearson correlation coefficients between the CBP and the plate-loaded bench press. Test-retest differences were analyzed with the paired t-test. ICC and CV for the men (r = 0.99, 1.4%) and women (r = 0.93, 3.5%), respectively indicate that highly reproducible 1RM scores can be found with the CBP. High validity was also found with high correlations between the CBP and plate-loaded bench press for the men (r = 0.95) and women (r = 0.80). A statistically significant (p = 0.04) but clinically small (2.57 kg) shift in the mean occurred between the CBP test and retest for the men, whereas no change occurred for the women. The data indicate that valid and reliable 1RM scores can be found after two familiarization sessions in men and women athletes who have previous resistance training experience.

THE REAR-FOOT-ELEVATED SPLIT SQUAT IS A MULTIJOINT EXERCISE USED TO TRAIN THE LOWER EXTREMITY MUSCULATURE IN ALL PLANES. THE BENEFITS INCLUDE PREVENTION OF LOWER EXTREMITY INJURY, IMPROVED GAIT AND SPORT PERFORMANCE, AND INCREASED MUSCLE SIZE AND STRENGTH. WITH AN ANTERIOR-POSTERIOR STANCE, THE EXERCISE IS PERFORMED PRIMARILY UNILATERALLY.

Recent evidence suggests an innovative approach to muscle conditioning: focal knee joint cooling (FKJC) appears to improve quadriceps function, including static (isometric) strength. However, there is limited evidence on the effects of FKJC on dynamic (concentric and eccentric) strength. Thus, the purpose of the study was to examine dynamic quadriceps strength following FKJC as well as static strength. Twenty-one college-aged participants volunteered. They randomly underwent 20 min of FKJC and control condition at least 72 h apart. FKJC involves two ice bags, placed on the anterior and posterior surfaces of the knee, whereas the control condition received a plastic ice bag filled with candy corn. We assessed isometric and isokinetic (concentric and eccentric) quadriceps strength at two different velocities (60°/s and 180°/s). Participants performed three maximal voluntary contractions for each mode of muscle contraction, before and after each treatment (immediately, 20, and 40 min after). The outcome variable was maximum knee extension peak torque. FKJC did not change peak torque during any mode of muscle contraction (p > 0.05). The current findings suggest that 20 min of FKJC does not change static (isometric) or dynamic (isokinetic) strength of the quadriceps. FKJC was neither beneficial nor harmful to static or dynamic muscular strength.