Footwear and Sex Differences in Performance and Joint Kinetics During Maximal Vertical Jumping

Abstract

Smith, RE, Paquette, MR, Harry, JR, Powell, DW, and Weiss, LW. Footwear and sex differences in performance and joint kinetics during maximal vertical jumping. J Strength Cond Res XX(X): 000-000, 2018-This investigation examined the effects of footwear and sex on vertical jump displacement and joint power contributions. Twenty-three young adults with basketball experience performed 3 maximal countermovement vertical jumps in minimal and standard footwear. Ground reaction force and 3D kinematic data were collected during jumping. Footwear by sex analysis of variance for all dependent variables and effect sizes (d) was computed. An interaction effect showed that men produced greater lower-limb-positive work than women in standard footwear. Men jumped higher than women (d = 2.53) and produced greater peak ankle, knee and hip joint moments (d > 0.99), positive joint powers (d > 1.07) and, positive knee and hip joint work (d > 1.04) with no sex differences for negative joint powers and work (p > 0.05). Minimal footwear produced less peak-positive knee power (d = 0.27) and less positive ankle (d = 0.34) and knee (d = 0.21) joint work than standard footwear. Because negative joint power and work were similar between sexes, men may be better able to use the stretch-shortening cycle compared with women. Higher joint mechanical demands may provide a better vertical jumping training stimulus in standard compared with minimal footwear. Future studies should investigate footwear training effects on performance and joint mechanics during jumping.

Single-Subject Analyses Reveal Altered Performance and Muscle Activation during Vertical Jumping

“…Accordingly, implementation of, and recommendation for, specific footwear conditions during a CMVJ test should be determined according to the individual and not the group. These results provide evidence to help explain the lack of consistency among previous group-based studies on the effects an acute change among barefoot, minimal, and conventional footwear on CMVJ performance [9,17,18]. Previous conclusions from group level studies should be interpreted with caution since the results of those studies might not accurately represent the sample of participants from which the "average" result was obtained.…”

“…It may seem reasonable to conclude that the inconsistent jump height results among previous studies centers on the types of footwear (brand, model, etc.) compared [9,17,18]. However, such a conclusion may be inappropriate because the footwear types compared in those studies all satisfy established categorical definitions for minimal and conventional footwear [3,20].…”

“…However, such an expectation may be premature given the results of a subsequent study in which CMVJ height and peak force production was not different among barefoot, minimal (Vibram Five Fingers KSO; Vibram Corp., North Brookfield, MA, USA), and conventional (New Balance MX623; New Balance, Inc., Boston, MA, USA) footwear conditions despite altered activations of some lower extremity muscles [17]. A recent follow-up study observed no differences in jump height between the same minimal and conventional footwear in men and women despite greater peak knee joint power production when wearing conventional footwear [18]. Although outside the scope of the barefoot/minimal versus conventional footwear debate, a recent comparison between conventional and maximal cushioned footwear observed no differences in CMVJ height or other kinetic variables driving CMVJ performance, such as the eccentric rate of force development, force at amortization, and joint angular power production and work [19].…”

“…The studies reporting no differences between or among footwear conditions [17][18][19] were carried out on samples estimated to provide sufficient statistical power for CMVJ performance. However, it is possible that key input parameters were inappropriate for the respective power analyses, such as using input data from a potentially underpowered sample [17], using self-selected input data use because of a lack of relevant literature [18], or inappropriateness of jump height for determining power for other variables (e.g., muscle activity). Still, the lack of clarity for footwear-driven changes during the CMVJ are likely due to large amounts of intra-individual (i.e., large trial-to-trial standard deviations) variability [21], inter-individual variability (i.e., large group standard deviations), or both, in the reported data.…”

“…In light of the information reviewed, assessments at the single-subject level [25] may be needed to reveal potentially worthwhile differences among footwear conditions. This may have value for human performance professionals aiming to quickly improve the jumping ability of an athlete through noninvasive methods, since previous group-based comparisons [9,17,18] suggest there is no "average" response to an acute change in footwear during jumping. Therefore, the purpose of this study was to determine whether barefoot and minimal footwear conditions alter CMVJ performance by way of force production and muscle activation in comparison to a conventional footwear condition, using a singlesubject analysis.…”