Award Date

May 2018

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Kinesiology and Nutrition Sciences

First Committee Member

Gabriele Wulf

Second Committee Member

James W. Navalta

Third Committee Member

Brach Poston

Fourth Committee Member

Bradley Donohue

Number of Pages

97

Abstract

Supporting performer autonomy has been consistently been shown to enhance motor learning (for reviews, see Sanli, Patterson, Bray, & Lee, 2013; Wulf, 2007; Wulf & Lewthwaite, 2016). Autonomy-supportive situations are those in which learners are given control over aspects of the practice conditions or are provided with other choices, including small and incidental choices that are not necessarily related to the task at hand. Providing autonomy support also benefits immediate motor performance, as demonstrated by enhanced punching velocity and impact forces in a study involving skilled kick boxers (Halperin, Chapman, Martin, Lewthwaite, & Wulf, 2016). Autonomy support is a key factor in the OPTIMAL theory of motor learning. Having a sense of autonomy is assumed to contribute to enhanced expectancies as a precondition for goal-action coupling (Wulf & Lewthwaite, 2016). The successful coupling of movement goals and necessary action is predicted to result in effective and efficient movement production. However, experimental evidence demonstrating effects of autonomy support on motor performance or movement efficiency is still lacking.

The purpose of this dissertation was to examine effects of autonomy support on motor performance, in particular movement efficiency. Three experiments were conducted to address this issue. Experiment 1 attempted to replicate the findings of Halperin et al. (2016) and examine their generalizability to non-athletes. Experiment 2 examined whether autonomy support would increase movement efficiency by including direct measures of movement efficiency (i.e., oxygen consumption, heart rate) during a submaximal run. Experiment 3 examined whether autonomy support would increase movement efficiency as measured by the use of surface electromyography (sEMG) while performing force production tasks at 3 different intensities.

The purpose of Experiment 1 was first study to determine whether providing autonomy support would enhance performers’ ability to maintain maximum force levels. Participants were asked to repeatedly produce maximum forces using a hand dynamometer under either choice or control conditions. After 2 initial trials with the dominant and non-dominant hand, choice group participants were able to choose the order of hands (dominant, non-dominant) for the remaining trials (3 per hand). For control group participants, hand order was determined by their yoked choice-group counterparts. The choice group was able to maintain the maximum forces produced on the first trial, while control group participants significantly showed a continuous decrease in force levels across trials. We interpret this finding as evidence that performers produced forces more efficiency under autonomy-supportive conditions.

A more direct measure of movement efficiency was used in the second study. Participants were asked to run at a submaximal intensity (65% of VO2 max) for 20 minutes. In the choice group, they were able to choose 5 of 10 photos (5 city, 5 nature motifs) as well as the order in which they were shown on a computer screen during the run. Participants in a control group were shown the same photos, in the same order, chosen by their counterparts in the choice group. Throughout the run, oxygen consumption and heart rate were significantly lower in the choice group than in the control group, indicating an increase in running efficiency. Thus, providing autonomy support may result in enhanced movement efficiency.

The third study examined muscle activity as a function of autonomy support by using sEMG. Participants were asked to perform a plantar flexion task at each of the 3 target torques, 80%, 50%, and 20% of maximum voluntary contractions (MVC). In the choice condition, participants were able to choose the order of 3 target torques. In the choice condition, participants were informed about order of torques (which was determined by the order chosen by another participant). EMG activity of gastrocnemius muscle was significantly lower in the choice condition relative to the control condition, while the similar torques were produced under both conditions. Thus, the choice condition allowed participants to perform at the same target force with less neuromuscular activity, indicating an increase in movement efficiency.

Overall, the dissertation findings add to increasing evidence that providing performers choices as a form of autonomy support has an immediate impact on motor performance. Experiment 2 and 3, in particular, provide direct evidence of enhanced movement efficiency (reduced oxygen consumption, heart rate, EMG activity) resulting from autonomy support. Overall, the current findings are in line with notion that autonomy support facilitates the coupling of movement goals and actions (Wulf & Lewthwaite, 2016). Practitioners can take advantage of these effects to not only to facilitate motor learning, but also to enhance motor performance or movement efficiency.

Keywords

Choice; EMG; Motor performance; Movement economy; Oxygen consumption; Self-control

Disciplines

Kinesiology

Language

English


Included in

Kinesiology Commons

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