Cross-Limb Transfer of Motor Skills: Mental Practice of Non-Dominant Hand Benefits Contralateral Limb

This paper investigates the question: Does the mental practice of the non-dominant hand enhance its performance and the performance of the contralateral limb? The study involved 16 handball players who engaged in mental exercises focused on their non-dominant hands during practice. The findings indicate that the mental practice of one limb positively influences the performance of the opposite, or contralateral, limb. The conclusion is that enhancing contralateral limb performance is a valuable strategy in athletic training, contributing to holistic development and optimizing an athlete’s potential, as well as proving beneficial in rehabilitation and motor skill acquisition.

Introduction

Mental training helps improve performance, but the question arises whether it facilitates the transfer of performance to the opposite side or the symmetrical part of the body. Does it facilitate the transfer of skills to the opposite or symmetrical side of the body? While there are various definitions of mental training, the most crucial one is that it is the mental representation of performance without the actual execution of the skill. Numerous studies have demonstrated the transfer of learning or skill from one side of the body to the other. However, does practicing or improving one side automatically lead to enhancements on the other side? The significance of mental training in learning and achievement is clear, as it aids in transferring motor commands and preparing motor nerves before performance begins. This principle has been applied across multiple scientific fields, particularly in rehabilitation and post-cardiac or stroke recovery. In sports, our focus is on developing motor complexes rather than relying solely on one side, which can limit the overall motor skill range (Hardwicket al., 2018; Jiménez-Díazet al., 2024; Mizuguchi & Kanosue, 2017; Nakashimaet al., 2024).

When discussing the dominant vs. non-dominant hand, it’s essential to note that the dominant hand is typically the one most frequently used for precise and skilled tasks, such as writing or throwing a ball. This hand generally exhibits greater strength and coordination due to more practice. Conversely, the non-dominant hand is less utilized for these tasks, resulting in comparatively lower strength and coordination, although it remains vital for support and balance in various activities. Most individuals are either right-handed (with the right hand as dominant) or left-handed (with the left hand as dominant), while some are ambidextrous and able to use both hands equally well. In sports, the distinction between dominant and non-dominant hands is significant, as it can impact performance and technique.

Coordination tends to be superior in the dominant hand, making it ideal for activities requiring fine motor skills and precision, such as dribbling a basketball or throwing a baseball (Crottiet al., 2022; Hugheset al., 2011; Iwatsukiet al., 2017). Training both hands, including the non-dominant one, can provide athletes with a competitive advantage (Rajaratnamet al., 2022; Schacket al., 2014; Simonsmeieret al., 2018; Wohldmannet al., 2008; Wulf & Lewthwaite, 2016).

The transfer of motor skills in sports refers to the ability to apply skills learned from one activity to another. This concept is particularly beneficial for athletes seeking to enhance their overall performance. An athlete skilled in throwing a baseball may find it easier to learn to throw a football or javelin due to the similarities in basic motion and coordination (Jiménez-Díazet al., 2024; Nakashimaet al., 2024).

Transferability is more effective when the cognitive and physical demands of the tasks are akin, encompassing mental practice, reaction time, decision-making, and movement patterns (Hurst & Boe, 2022; Laures-Goreet al., 2021; Tothet al., 2020; Villa-Bergeset al., 2023). The cross-training of limb transfer through mental practice is crucial, as mental practice constitutes a cognitive demand for transferring motor tasks (Kanget al., 2019; Lohseet al., 2010; Wehlmann & Wulf, 2021; Yamaguchiet al., 2015). Consequently, this study aims to explore how the mental practice of the non-dominant hand affects the dominant hand.

Method

Participants

A total of 16 students (Mean_age = 22, SD_age = 2.6) participated in this experiment. They met all requirements for volunteering and provided informed consent, which was approved by the Education College Ethics Committee at Mustansiriyah University. All participants reported being in good health, had no history of disease, and were not receiving any medical treatment that could affect their motor or visuomotor functions. The final sample size of 16 offers 75% power to detect effects with d > 0.73.

Materials and Apparatus

The experiment utilized a handball goal measuring 9.28 ft in width and 6.56 ft in height. The goalposts have a bottom depth of 3.28 ft and a top depth of 2.62 ft, with these height and width dimensions excluding the thickness of the posts. Additionally, two squares, each measuring one meter, were placed in each corner of the goal. Participants attempted to throw the ball from a distance of 9 meters upon hearing the signal to start.

Design and Procedure

Each participant had five attempts using both their dominant and non-dominant hand. A failed attempt resulted in a deduction of one point, while a successful attempt earned one point. In the second trial, mental practice was implemented for the non-dominant hand before each attempt. Each hand was given five attempts.

Results

The results of experiment for t(15) = 4.162, p < 0.008, d = −0.64, indicating highly significant results. Participants achieved more successful trials during performance execution. Additionally, for the dominant hand, the results were t(15) = 8.918, p < 0.001, d = −0.68. Overall, the one-way ANOVA yielded F(15) = 10.48, p = 0.001. Tables I and II present a detailed summary of the analysis.

Table I. Descriptive Statistics for Both the Dominant and Non-Dominant Hands

Groups	Count	Sum	Average	Variance
Dominant	16	19	1.187	5.629
Non-dominant	16	−14	−0.875	2.250
Dominant	16	40	2.500	2.533
Non-dominant	16	5	0.312	1.962

Table II. Results of the One-way ANOVA Comparing the Non-Dominant and Dominant Hands

Source of variation	SS	df	MS	F
Between groups	97.312	3	32.437	10.485
Within groups	185.625	60	3.0937
Total	282.937	63

The results for all attempts of the dominant and non-dominant foot before mental practice clearly show that the dominant hand outperformed the non-dominant hand, as illustrated in Fig. 1. However, Fig. 2 demonstrates that after engaging in mental rehearsal, the non-dominant hand performed better. This outcome indicates that mental training, which also influenced the dominant hand, led to an improvement and transfer of motor skills to the contralateral limb.

Fig. 1. Data without mental practice for the non-dominant and dominant hand.

Fig. 2. Data with used mental practice for the dominant and non-dominant hand.

Discussion

Mental practice can be a powerful tool for transferring motor skills, especially when physical practice is limited. This study investigated whether the mental practice of the non-dominant hand could enhance and transfer its performance and the contralateral limb’s performance. The sample included 15 participants who engaged in mental training for their non-dominant hand during performance. The findings suggest that the mental practice of one limb can positively impact the opposite, or contralateral, limb’s performance (Nakashimaet al., 2024; Rajaratnamet al., 2022). This is a valuable insight, as fostering symmetrical limb performance is an important strategy in athletic training, promoting holistic development and optimizing an athlete’s potential, including in rehabilitation and sports training contexts (Tothet al., 2020; Wulf & Lewthwaite, 2016). Existing research has demonstrated the efficacy of mental practice in improving psychomotor performance and enhancing skill acquisition in various domains, including sports and music (Rajaratnamet al., 2022). The current study extends these findings, showing that the benefits of mental practice can cross over to the untrained limb. The results align with the notion that mental practice involves more abstract, effector-independent representations of the skill, which can then be applied to different body parts (Rajaratnamet al., 2022). The interaction between motor skill development and broader physical and cognitive functioning should not be underestimated. Motor development is a central focus in work with individuals with neurodevelopmental disorders, given its far-reaching impacts. In the context of athletic training, fostering symmetrical limb performance through mental practice may contribute to more holistic improvements, optimizing an athlete’s overall potential.

In conclusion, fostering symmetrical limb performance is a valuable strategy in athletic training, promoting holistic development and optimizing an athlete’s potential. It will also benefit from using this strategy, and the implications of such results are significant, particularly in the fields of rehabilitation and motor skills. In conclusion, fostering symmetrical limb performance is a valuable strategy in athletic training that promotes holistic development and optimizes an athlete’s potential. The implications of this strategy are significant, particularly in the fields of rehabilitation and motor skills.