Extended Abstract
Background and Purpose
The positive effect of mental practice on skill learning is considered a piece of evidence for similar underlying mechanisms of physical and mental practice. According to Newell’s model of motor learning, at the first stage of learning, the physical practice would enhance coordination and in the second stage practice would enhance control of that coordination pattern. In line with this argument, it has been shown that movement variability would reduce as a result of skill enhancement. Also, research showed that movement jerk would reduce as a result of skill improvement. According to the abovementioned argument, if the underlying mechanisms of mental and physical practice are similar, then mental practice should have a similar effect on movement variability and movement jerk. As this argument was not considered widely in previous studies, this study aimed to compare the effect of physical and mental practice on movement variability and movement jerk.
 Methods
30 males (mean = 25 ± 4.3) participated in this study according to a convenience sampling method. Participants were divided into three different groups (physical, mental, and control) according to their pre-test scores (10 trials from 244 cm away from the target). Also, before participating in the practice sessions, all participants completed the movement imagery questionnaire-revised. Then, participants practiced a golf putting task for 6 consecutive days (10 blocks—18 trials each). The physical practice group performed 180 trials each day (10 blocks) from 244 cm away from the target. The mental practice group completed the mental putting task while standing on the start point holding the putter, without any observable movement. The control group did not practice and just completed the pre- and retention tests. A retention test (similar to the pre-test) was performed seven days from the last practice session (10 trials from 244 cm from the target). Movement kinematics were recorded using a SIMI motion capture system to calculate the coordination and smoothness indexes. Putting accuracy (distance from the edge of the landed ball from the edge of the target), variability of coordination pattern, and movement jerk were calculated as the dependent variables. The imagery data were analyzed using a One-way ANOVA. All other data were analyzed using a mixed ANOVA model 3 (group; physical, mental, and control) × 2 (test; pre- and post-tests) with the repeated measures on the last factor.
Results
Results of One-way ANOVA for imagery data showed no significant difference between groups,
F < 1. For the accuracy data, results showed no significant main effect of group, F (2, 27) = 0.98, p = 0.38, η²p = 0.068. However, significant main effects for test, F (1, 27) = 10.21, p = 0.004, η²p = 0.27, and the interaction of group with test, F (2, 27) = 13.20, p < 0.001, η²p = 0.49, were found. The results of post-hoc test for the interaction effect showed that there was no significant difference between groups during the pre-test, all p > 0.05. However, the physical practice showed higher accuracy than the imagery practice group during the post-test, p < 0.05. Also, accuracy improvements were observed for physical and imagery groups from pre to post-test, all p < 0.05; no such effect was observed for the control group, p > 0.05. Results for variability of coordination pattern showed no significant main effect for group, F (2, 27) = 1.08, p = 0.35, η²p = 0.07. However, significant effects were observed for test, F (1, 27) = 63.63, p < 0.001, η²p = 0.7, and interaction of group × test, F (2, 27) = 15.38, p < 0.001, η²p = 0.53. Post-hoc test for the interaction effect showed that there was no significant difference between groups during the pre-test, all p > 0.05. Results showed that during the retention test physical and imagery groups significantly outperformed the control group, all p < 0.05. The difference between the physical and imagery groups was not significant during the retention test, p > 0.05. Also, results showed improvement from pre-test to retention test for physical and imagery groups, all p < 0.05; such effect was not observed for the control group, p > 0.05. Results of ANOVA for the jerk measure showed significant main effects for group, F (2, 27) = 5.68, p = 0.009, η²p = 0.29, and test, F (1, 27) = 33.78, p < 0.001, η²p = 0.55. Also, the interaction effect of group × test was significant, F (2, 27) = 15.26, p < 0.001, η²p = 0.53. Results of post-hoc test for the interaction showed no significant difference between groups during the pre-test, all p > 0.05. However, results showed that the physical group had significantly lower movement jerk than the imagery and control groups, all p < 0.05. Also, results showed improvement from pre-test to retention test for physical and imagery groups, all p < 0.05; like other measures, such effect was not observed for control group, all p > 0.05.
 Conclusion
Although mental practice improved movement accuracy, this improvement was not equal to or more than improvements by physical practice. These findings were considered as evidence for different underlying mechanisms for physical and mental practice (8,9,10). It is argued that internal models would not update during motor imagery (11), and as a result, learning may suffer. In contrast to the previous study (12), this study showed that mental practice would improve the variability of movement coordination similar to physical practice. In the previous study, a discrete measure of variability was used which has some limitations to show differences between groups (13,14); however, in this study a continuous measure was used. Also, in the previous study participants just performed 18 trials, in this study participants performed 1080 practice trials. The difference in the amount of practice could serve as a possible reason for contradicting findings. Besides, results showed that motor imagery practice improved movement smoothness but was lower than physical practice. The lack of real visual feedback could be the possible reason for this finding (8).
Article Message
The results of this study showed that mental practice, like physical practice, leads to learning the golf stroke. The results also indicated that mental practice improves movement smoothness; however, this improvement was not as significant as that achieved through physical practice.
Ethical Considerations
This study was reviewed and approved by the Ethics Committee of Shiraz University.
Authors’ Contributions
Conceptualization: Davoud Fazeli, Hamidreza Taheri, Alireza Saberi Kakhki
Data Collection: Davoud Fazeli
Data Analysis: Davoud Fazeli, Hamidreza Taheri, Alireza Saberi Kakhki, Fatemeh Shakeri Chenari
Manuscript Writing: Davoud Fazeli, Hamidreza Taheri, Alireza Saberi Kakhki, Fatemeh Shakeri Chenari
Review and Editing: Davoud Fazeli, Hamidreza Taheri, Alireza Saberi Kakhki, Fatemeh Shakeri Chenari
Responsible for funding: No funding.
Literature Review: Davoud Fazeli, Hamidreza Taheri, Alireza Saberi Kakhki, Fatemeh Shakeri Chenari
Project Manager: Davoud Fazeli
Any other Contributions: No other contributions
Conflict of Interest
The author(s) declare that there is no conflict of interest regarding the publication of this article.
 
Acknowledgments
The author(s) would like to express their sincere gratitude to the participants who made this study possible.