The aim of the present study was to evaluate the short-term effects of ST on strength and power performances, also in relation to gender. The main findings of the present study were that ST elicited acute improvements in strength and power performances in males only.
In line with the literature [41
], regardless of the experimental condition, males showed better performances with respect to females. After the ST session, gender-related acute improvements in strength and power were observed. In particular, males reported higher values in SJ, CMJ, and MVC (regardless of limb dominance), whereas no changes emerged in females.
Contrasting results have been reported investigating the short-term effects of ST exercises, with a study showing sport-specific acute improvements in strength, power and velocity of execution [20
], and others reporting reductions in isometric force production [25
]. Although after an acute bout of exercise, a deterioration in performance could be expected due to fatigue [43
], exercise-related arousing effects have been reported in complex motor behaviors regardless of age and expertise [29
]. Therefore, the acute improvements in jump performances found in males after the ST session (CMJ: +4.6%; SJ: +4.3%), could be attributed to the increases in psychomotor speed and central executive control functions exerting a preservative effect on the efficiency of those executive attentional processes involved in the control of complex motor behavior [45
]. Jump performances represent a complex coordinative task resulting from the interaction between the force of contraction and speed of movement (i.e., power), thus, it is likely that CMJ and SJ performances could be more affected by acute bouts of exercise than static strength [46
]. In fact, acute reductions (or no changes) in isometric force production have been reported after ST exercises and sports competitions [25
], in which the authors attributed to fatigue due to the specific involvement of the limbs during the activity. As ST session used in the present research included both upper and lower limbs exercises, similar findings could have been expected, with decrements or no changes in upper and lower limbs strength production. Conversely, increases in strength performances (MVC) were found, although gender differences emerged. In particular, males showed significant increases in MVC (dominant limb: +7.7%; non-dominant limb: +6.1%), whereas no effects emerged in females. During ST sessions, the evaluation of the load distribution during each exercise could be affected by several biomechanical aspects, such as the body inclination, the length of ST device, the feet position, and the combination of these factors [3
]. Therefore, it is possible that participants performed each exercise in the most comfortable position, thus leading to exercise-related arousal rather than fatigue in strength parameters. Moreover, ST could be classified as moderate-to-vigorous intensity exercise [6
] and the nature of the lesson used in this study (designed to alternate exercises for core, lower and upper body on the unstable surface) stressed the neuromuscular system providing an exercise intensity and duration exerting arousing effects on performances in lower limbs. As while performing most of the ST exercises included in the lesson, the participants are required to isometrically hold the two moving handles even when performing dynamic exercises, it could be speculated that the isometric activity did not exert any beneficial arousing effect on grip strength.
Females showed no significant changes in performances. Similar findings were found for power athletes [47
], in which studying the gender-related acute effects of resistance exercise on strength and power performances among other factors, no gender differences emerged investigating the acute effects of performing back squats on subsequent performance [48
]. As the existing literature mainly focused on males or reported non-conclusive findings, it could only be speculated that female participants did not benefit from the exercise-related arousing effects observed in males. For MVC, males showed improvements regardless of limb dominance, whereas no significant change emerged in females. Although the literature reported gender-related differences in acute response to exercise due to muscular fatigue [49
], it seems that short-term effects after ST are somehow limb-specific. In conclusion, the current results indicate that ST is a form of exercise exerting short-term increases in strength and power performances in male participants. Considering that no reductions emerged in both strength and power performances regardless of gender, ST could also be used in different warm-up exercises in sports and activities where these characteristics play a key role. However, future studies are encouraged to further explore the gender-related differences in response to an acute bout of exercise, as the results are still not exhaustive.