Acute Effects of Trampoline Training Session on Leg Stiffness

Purpose: SuperJump® workout is an innovative training modality that allows aerobic work by making the most of the potential of a jump training. Unlike jumping on the floor, it minimizes the stress on the joints, thus lowering the risk of microtraumas and injuries. Although SuperJump® is thought to stimulate higher muscle activations than traditional floor jumping exercises, only limited information is available on its acute effects on lower limbs stiffness performance. Therefore, this study aimed to evaluate the acute effects of a SuperJump® workout on lower limb stiffness, also in relation to sex. Methods: 20 participants (11 females, age: 24.4±1.0 yrs; 9 males, age: 27.3±2.9 yrs) were administered continuous jump repetitions (CJs) before (PRE) and after (POST) a 30-min SuperJump® session including a warm-up with breathing and mobility exercises, a central phase with jumping exercises alternating movements of the upper and lower limbs and a cool-down phase. The CJs testing session consisted of 3 trials (5 CJs at preferred jumping Hz) with a 1-min recovery in between. They were asked to jump upwards without bending the knees with the arms on the hips and were instructed to jump as high as possible and as fast as possible. For each of the 3 trial the means of the 5 CJs was taken into consideration. Data were collected by a Quattro Jump force plate connected with a data acquisition system by means of a charge amplifier that allows the detection of force, power, and flight time. Vertical stiffness was evaluated by dividing the peak change in vertical force by the change in vertical displacement during contact. Multilevel regression models were performed to examine the effects of a SuperJump® training session on the subject’s stiffness in relation to sex. After Bonferroni correction statistical significance was set at p <0.008. Results: No sex differences emerged. For both sexes, lower limb stiffness slightly decreased after SuperJump® training, however no significant differences were found from PRE to POST values. Women reported lower stiffness values than men both PRE (females: 23.94±4.21 kN/m, males: 38.77±9.41 kN/m) and POST (female: 23.83±2.71 kN/m, males: 38.09±9.53 kN/m). Conclusions: Findings indicate that SuperJump® as a form of exercise is useful to maintain and improve leg stiffness performances. However, it would also be necessary to record neurophysiological parameters to evaluate the possible mechanism underlying the observed stiffness variations.