A comparison of countermovement jump performance and kinetics at the start and end of an international Rugby Sevens season

The countermovement jump (CMJ) is used to profile and monitor lower body neuromuscular performance in a variety of sports. While jump height, peak power and peak force are commonly reported CMJ variables (CMJ-TYP), several temporal and rate-limited kinetic “alternative” (CMJ-ALT) variables have shown greater response to acute and chronic load, but this has not been examined in male Rugby Sevens (7s) athletes. We evaluated changes in CMJ-ALT and CMJ-TYP variables at the start and end of a World 7s Series season. We compared mean values for CMJ-ALT and CMJ-TYP variables in three CMJs performed by elite male rugby 7s players (n = 12) close to the start and at the end of the season. Potential differences were determined with repeated measures t-tests and magnitude of change quantified using effect sizes. Comparing the start and the end of the season, there were significant differences with very large and large effect sizes in concentric peak force and in a number of CMJ-ALT variables such as concentric duration, countermovement depth, concentric impulse-100ms, concentric rate of power development, eccentric deceleration rate of force development, RSI-modified and FT:CT, with effect sizes ranging between d = 0.98 to 1.39 and p values ranging between p < 0.001 to 0.04. There was no significant change in jump height or concentric peak power. Season-long exposure to matches and training blocks led to improvements in specific CMJ kinetic variables, the majority which were temporal or rate-limited kinetic or CMJ-ALT variables, but not in jump height and peak power or eccentric deceleration impulse. When aiming to quantify chronic response to loading using the CMJ, monitoring of a limited number of ‘typical’ variables may lead to misleading null conclusions about the response of these athletes to long-term/season long loading. In contrast, a more comprehensive kinetic analysis may reveal improvements in aspects of neuromuscular performance.