UNEVEN ARM LOAD AND RHYTHMIC ARM COORDINATION

Abstract

Bilateral limb coordination has been examined for different types of locomotion from basic movements, such as walking, to movements that require more coordination, such as those performed while swimming. Although many studies have examined the effects of coordination while walking, examining the effects of coordination while swimming has been difficult to do even though both are bilateral rhythmic movements. Changes or differences in the metabolic cost during movements in air cause relatively small, but important, differences in economy and/or efficiency. These differences may be on the order of a percentage or two. However, non-coordinated movements in the water during propulsion can cause differences in economy and/or efficiency of 50 to 100 or more percent. The purpose of the current study was to investigate the metabolic cost of arm coordination occurring with a change in load distribution between two arms. Eleven competitive swimmers (men age 21.4 ± 4.4 yrs) performed a discontinuous maximal aerobic capacity test and an arm coordination test (AT) on a modified pulley weight stack, which is similar to a swim bench. The AT consisted of three randomized trials with workloads based on the subject’s peak oxygen consumption (VO2Peak). The three trials consisted of a workload corresponding to 50% of workload at the subject’s VO2Peak (WL1), a workload corresponding 65% of workload at VO2Peak (WL2), and a workload corresponding 80% of workload at VO2Peak (WL3). Within each trial there were three randomized arm loading profiles: even arm load distribution (EL) and two uneven arm load distributions, right arm loading (RL) and left arm loading (LL). Subjects were instructed to mimic a front crawl pull throughout the 5-minute exercise bouts. Arm coordination was determined using the index of coordination (IdC) (Chollet, 2001) which expressed the percentage of the total stroke when no propulsive forces were made by the subject. Oxygen consumption (VO2) and heart rate were measured in minute and 30-second intervals respectively. The mean VO2 of the subjects significantly increased from WL1 to WL2 and WL3 (p < 0.05); however, there were no significant differences in VO2 within each trial. Mean IdC for both the left and right arms were not significantly different within each trial and between trials (p > 0.05). The mean stroke lengths of the right arm were not significantly different from the left arm, with the exception of the LL at WL2 (1.08±0.20 m, 0.98±0.11 m) (p = 0.002) and LL at WL3 (1.12±0.23 m, 1.00±0.09 m) (p = 0.003). This was the first study to examine arm coordination on swimmers out of the water and to modify the workload placed on each arm. The results from the study suggest that the uneven load profiles did not have an effect on either the metabolic demand of the movement or the coordination of the arms while on the MPWS. Future research is needed to compare coordination patterns while swimming in and out of the water.