Potential Mediators of Load-Related Changes in Movement Complexity in Young, Healthy Adults.

Abstract

CONTEXT\nMovement screening has become increasingly popular among tactical professionals. This popularity has motivated the design of interventions that cater to improving outcomes on the screens themselves, which are often scored in reference to an objective norm. In contrast to the assumptions underlying this approach, dynamical systems theory suggests that movements arise as a function of continuously evolving constraints and that optimal movement strategies may not exist. To date, few data address behavioral complexity in the fundamental movement tasks commonly used in clinical screenings.\n\n\nOBJECTIVE\nTo provide evidence of complex variability during movement screens and test the role of modifiable-that is, trainable-constraints in mediating loss of complexity during experimental-task manipulations.\n\n\nDESIGN\nCrossover study.\n\n\nSETTING\nResearch laboratory.\n\n\nPATIENTS OR OTHER PARTICIPANTS\nTwenty-five male (age = 23.96 ± 3.74 years, height = 178.82 ± 7.51 cm, mass = 79.66 ± 12.66 kg) and 25 female (age = 22.00 ± 2.02 years, height = 165.40 ± 10.24 cm, mass = 63.98 ± 11.07 kg) recreationally active adults.\n\n\nINTERVENTION(S)\nParticipants performed tests of balance, range of motion, and strength. Additionally, they performed cyclical movement tasks under a control (C) condition and while wearing an 18.10-kg weight vest (W).\n\n\nMAIN OUTCOME MEASURE(S)\nGround reaction forces were sampled at 1000 Hz and used to calculate center of pressure during cyclical movement tests. Multivariate multiscale entropy (MMSE) for the center-of-pressure signal was then calculated. Condition effects (C versus W) were analyzed using paired t tests, and penalized varying-coefficients regression was used to identify models predicting entropy outcomes from balance, range of motion, and strength.\n\n\nRESULTS\nThe MMSE decreased during the W condition (MMSEC > MMSEW; t49 range = 3.17-5.21; all P values < .01).\n\n\nCONCLUSIONS\nModerate evidence supported an association between modifiable constraints and behavioral complexity, but a role in mediating load-related loss of complexity was not demonstrated.