The Influence of Load and Speed on Individualsʼ Movement Behavior

• Published in: Journal of strength and conditioning research 2015-09, Vol.29 (9), p.2417-2425
• Main Authors: Frost, David M, Beach, Tyson A.C, Callaghan, Jack P, McGill, Stuart M
• Format: Article
• Language: English
• Subjects: Adult; Firefighters; Humans; Knee Joint - physiology; Load; Male; Middle Aged; Movement; Movement - physiology; Occupational Injuries - etiology; Occupational Injuries - prevention & control; Random Allocation; Spine - physiology; Sports injuries; Training; Variables; Velocity; Weight-Bearing
• ISSN: 1064-8011; 1533-4287
• DOI: 10.1519/JSC.0000000000000264

ABSTRACTFrost, DM, Beach, TAC, Callaghan, JP, and McGill, SM. The influence of load and speed on individualsʼ movement behavior. J Strength Cond Res 29(9)2417–2425, 2015—Because individualsʼ movement patterns have been linked to their risk of future injury, movement evaluations have become a topic of interest. However, if individuals adapt their movement behavior in response to the demands of a task, the utility of evaluations comprising only low-demand activities could have limited application with regard to the prediction of future injury. This investigation examined the impact of load and speed on individualsʼ movement behavior. Fifty-two firefighters performed 5 low-demand (i.e., light load, low movement speed) whole-body tasks (i.e., lift, squat, lunge, push, and pull). Each task was then modified by increasing the speed, external load, or speed and load. Select measures of motion were used to characterize the performance of each task, and comparisons were made between conditions. The participants adapted their movement behavior in response to the external demands of a task (64 and 70% of all the variables were influenced [p ≤ 0.05] by changing the load and speed, respectively), but in a manner unique to the task and type of demand. The participants exhibited greater spine and frontal plane knee motion in response to an increase in speed when compared with increasing loads. However, there were a large number of movement strategies exhibited by individual firefighters that differed from the groupʼs response. The data obtained here imply that individuals may not be physically prepared to perform safely or effectively when a taskʼs demands are elevated simply because they exhibit the ability to perform a low-demand activity with competence. Therefore, movement screens comprising only low-demand activities may not adequately reflect an individualʼs capacity, or their risk of injury, and could adversely affect any recommendations that are made for training or job performance.