The relationship between conscious movement investment and motor inhibition
Authors:   , You Yihong 
Published: June 2024

Motor inhibition refers to the ability to suppress unwanted or inappropriate behaviors. Unlike the ballistic movements often studied in laboratories, athletes frequently need to stop more complex movements during sports activities. These movements are often prolonged and can be altered, occurring automatically or unconsciously. However, automatized control does not always persist in sports environments, raising questions about motor inhibition in competitive sports compared to laboratory settings. This thesis addresses the issues related to motor inhibition.
We initially aimed to investigate whether motor inhibition is amodal or embodied. In Chapter 2, we explored the potential for computer-based training of motor inhibition by comparing motor inhibition on the stop signal task (SST) in pre- and post-tests between an experimental group and a control group. The experimental group received ten training sessions on a modified SST, while the control group trained on a choice reaction time task. This study found evidence of no change in the speed of motor inhibition during or after training, suggesting that motor inhibition is difficult or impossible to improve.
Due to the lockdown, we adjusted our research focus to examine the impact of conscious movement investment on motor inhibition. In Chapter 3, we conducted three online experiments. Experiment 1 had participants perform the go/no-go task with conscious movement investment manipulated by directing attention either to the finger movements or to the resulting motion of the key. Experiments 2 and 3 involved the more demanding SST, with Experiment 3 including an ego-depletion procedure to reduce resources for conscious movement investment. Participants also completed the Movement-Specific Reinvestment Scale (MSRS) to measure their inclination for conscious movement investment. Experiment 1 revealed no differences in motor inhibition rates between the groups. Similarly, Experiment 2 found no differences in motor inhibition speed between individuals with high and low inclinations for conscious movement investment. However, Experiment 3 showed that participants with a high inclination for conscious movement investment slowed down inhibition when mentally depleted, while those less depleted or with a low inclination did not.
Chapters 4 and 5 investigated the same question using a more complex task with multiple degrees of freedom: a golf putting task. In Chapter 4, novice golfers were asked to putt balls and occasionally stop upon hearing an auditory cue during the downswing. Participants also completed the MSRS and verbal knowledge protocols. Results showed that participants with a higher inclination for conscious movement monitoring had a higher stopping rate but longer stopping time compared to those with a lower inclination. Movement kinematics suggested that a higher inclination for conscious movement monitoring was accompanied with a slower downswing, enabling successful but late stops.
Chapter 5 directly manipulated the degree of conscious movement investment by comparing changes in inhibition after instructional interventions aimed at expanding or limiting conscious investment in executing a golf putting task. The task was identical to Chapter 4, with participants performing it before and after practicing a normal golf putting task with interventions. After the post-intervention test, verbal knowledge protocols were administered. Results showed no significant differences in inhibition performance between the two instructional interventions. However, mediation analysis confirmed that the intervention aimed at expanding conscious movement investment resulted in greater changes in downswing time between tests compared to the intervention aimed at limiting conscious investment. This increased change in downswing time correlated with amplified changes in both stopping rate and stopping time.
Based on the findings from Chapters 3 to 5, we concluded that conscious movement investment influences inhibition performance, but this effect depends on the interaction of various constraints.