The purpose of this study was to find which percentage of 1RM for squat to improve the result of squat jump most effectively after plyometric training with different percentage of 1RM for squat. 24 men in their twenties were measured 1RM for squat and separated in 4 groups by 6 participants. Group A, B, C, and D used 0, 15, 30, and 45% of 1RM, respectively in the plyometric training. All groups had 1 hour training 3 days per week for 8 weeks(24 sessions). This study designed to increase the number of sets of exercises gradually. In week 1 and 2, participants trained 1 set of plyometrics with no load. The number of sets increased 2 to 4 in the week 3-4 to 7-8. The jump height(cm) and vertical impulse(%BW) of squat jump before and after plyometric training were measured by 3D motion capture system and force plate. All 4 groups showed the improvement of squat jump height and vertical impulse, but specially group B was most improved(p<0.5).
The human foot is only part that directly contact between the body and the external environment, and is ideally positioned to provide sensory information to the Central Nervous System (CNS) during static and dynamic tasks. Through cutaneous mechanoreceptors located in the dermis, the foot is able to recognize touch pressure and vibration stimuli, which provide important feedback information used for the fine coordination of movements. The purpose of this study is to quantitatively examine the effect of changing the foot cutaneous sensory by temperature stimulus on maximal performance and muscle activation using wavelet technique. Sixteen healthy subjects volunteered to participate in this study (Male: Age 21.4±2.4years; Height 174.7±5.3츠; Weight 70.6±5.2kg; Female: Age 20.5±0.6years; Height 163.2±3.1cm; Weight 55.6±4.8kg). Sensory pressure thresholds were determined for the plantar surface of the foot using monofilament. Kinematic, kinetic and EMG data which relative to maximal performance were collected while squat jumping in each temperature condition(cool 12-15℃ normal 28-30℃ hot 45-48℃). Maximal jump height was significant higher in normal condition. Vertical GRF in normal condition showed higher peak value the other conditions. And then EMG signal were significant different between temperature conditions during maximal performance. By changed sensory feedback on temperature, one can alter maximal performance and muscle activation pattern. Cutaneous feedback is important in performance and neuromuscular control, and temperature changes significantly influence on lower extremity during maximal squat jump performance of healthy subjects.
