No abstract

The purpose of this study was to examine the effectiveness of maximal and rapid isometric torque characteristics of the hip extensor muscles and postural balance performance to discriminate between female collegiate soccer athletes and non-athlete controls. Ten athletes (mean ± SE: age = 19·20 ± 0·36 year; mass = 62·23 ± 3·12 kg; height = 162·43 ± 1·70 cm) and 10 non-athletes (age = 20·30 ± 0·40 year; mass = 69·64 ± 3·20 kg; height = 163·22 ± 2·10 cm) performed two isometric maximal voluntary contractions (MVCs) of the hip extensor muscles. Peak torque (PT) and absolute and relative rate of torque development (RTD) at early (0-50 ms) and late (100-200 ms) phases of muscle contraction were examined during each MVC. Postural balance was assessed using a commercially designed balance testing device, which provides a measurement of static stability based on sway index (SI). Results indicated that absolute and relative RTD at 0-50 ms (RTD50 and RTD50norm) were greater (P = 0·007 and 0·026), and postural SI was lower (P = 0·022) in the athletes compared with the non-athletes. However, no differences (P = 0·375-0·709) were observed for PT nor absolute and relative RTD at 100-200 ms (RTD100-200 and RTD100-200norm). Significant relationships were also observed between RTD50 and RTD50norm and SI (r = -0·559 and -0·521; P = 0·010 and 0·019). These findings suggest that early rapid torque characteristics of the hip extensor muscles and postural balance performance may be sensitive and effective measures for discriminating between college-aged athletes and non-athletes. Coaches and practitioners may use these findings as performance evaluation tools to help in identifying athletes with both superior early rapid torque and balance performance abilities, which may possibly be an indicator of overall athletic potential.

Early rapid strength production of the hip extensor muscles may be a sensitive and effective measure for discriminating between elderly females of different fall histories. These findings may provide important insight regarding implications for the assessment of fall risk and in the development of proper training programs aimed at minimizing the occurrence of falls and other balance-related injuries in the elderly.

The aim of this study was to examine the effects of a medium-intensity high-volume vs. explosive squat protocol on the postexercise time course responses of maximal and rapid strength of the knee extensors. Seventeen resistance-trained men (mean ± SD: age = 22.0 ± 2.6 years) performed maximal voluntary contractions (MVCs) of the knee extensors before and after performing a squat workout using either a low-intensity fast velocity (LIFV) (5 × 16 at 40% 1 repetition maximum) or a traditional high-intensity slow velocity (TISV) (5 × 8 at 80% 1RM) exercise protocol. For each MVC, peak torque (PT), peak rate of torque development (RTDpeak), absolute (RTDabs), and relative RTD (RTDnorm) at early (0-50 milliseconds) and late (100-200 milliseconds) phases of muscle contraction were examined at pre- (Pre) and post-exercise at 0, 7, 15, and 30 (Post0...30) minutes. There were no intensity × time interactions for any variables (p = 0.098-0.832). Peak torque was greater at Pre than Post0 and Post7 (p = 0.001-0.016) but was not greater than Post15 and Post30 (p = 0.010-0.189). RTDpeak and early absolute RTD (RTD50abs) were greater at Pre than all postexercise time phases (p = 0.001-0.050); however, later absolute RTD (RTD100-200abs) was only greater at Pre than Post0 and Post30 (p = 0.013-0.048). Early relative RTD (RTD50norm) was only higher at Pre compared with Post0 (p = 0.023), whereas no differences were observed for later relative RTD (RTD100-200norm) (p = 0.920-0.990). Low-intensity fast velocity and TISV squat protocols both yielded acute decreases in maximal and rapid strength capacities following free-weight squats, with rapid strength showing slower recovery characteristics than maximal strength.

Hester, GM, Pope, ZK, Sellers, JH, Thiele, RM, and DeFreitas, JM. Potentiation: Effect of ballistic and heavy exercise on vertical jump performance. J Strength Cond Res 31(3): 660-666, 2017-The purpose of this study was to compare the acute effects of heavy and ballistic conditioning protocols on vertical jump performance in resistance-trained men. Fourteen resistance-trained men (mean ± SD: age = 22 ± 2.1 years, body mass = 86.29 ± 9.95 kg, and height = 175.39 ± 9.34 cm) with an average relative full squat of 2.02 ± 0.28 times their body mass participated in this study. In randomized, counterbalanced order, subjects performed two countermovement vertical jumps before and 1, 3, 5, and 10 minutes after either performing 10 rapid jump squats or 5 heavy back squats. The back squat protocol consisted of 5 repetitions at 80% one repetition maximum (1RM), whereas the jump squat protocol consisted of 10 repetitions at 20% 1RM. Peak jump height (in centimeters) using a jump mat, along with power output (in Watts) and velocity (in meters per second) through a linear transducer, was recorded for each time interval. There was no significant condition × time interaction for any of the dependent variables (p = 0.066-0.127). In addition, there was no main effect for condition for any of the dependent variables (p = 0.457-0.899). Neither the ballistic nor heavy protocol used in this study enhanced vertical jump performance at any recovery interval. The use of these protocols in resistance-trained men to produce postactivation potentiation is not recommended.