Purpose: We investigated motor-respiratory coordination (MRC) in visually guided forearm tracking movements focusing on two main questions: (1) Does attentional demand, training or complexity of the tracking task have an effect on the degree of MRC? (2) Does MRC impair the precision of those movements? We hypothesized that (1) enhanced attention to the tracking task and training increase the degree of MRC while higher task complexity would reduce it, and (2) MRC impairs tracking precision. Methods: Thirty-five volunteers performed eight tracking trials with several conditions: positive (direct) signal–response relation (SRR), negative (inverse) SRR to increase task complexity, specific instruction for enhanced attention to maximize tracking precision (“strict” instruction), and specific instruction that tracking precision would not be evaluated (“relaxed” instruction). The trials with positive and negative SRR were performed three times each to study training effects. Results: While the degree of MRC remained in the same range throughout all experimental conditions, a switch in phase-coupling pattern was observed. In conditions with positive SRR or with relaxed instruction, we found one preferred phase-relationship per period. With higher task complexity (negative SRR) or increased attentional demand (strict instruction), a tighter coupling pattern with two preferred phase-relationships per period was adopted. Our main result was that MRC improved tracking precision in all conditions except for that with relaxed instruction. Reduction of amplitude errors mainly contributed to this precision improvement. Conclusion: These results suggest that attention devoted to a precision movement intensifies its phase-coupling with breathing and enhances MRC-related improvement of tracking precision.

Purpose: We investigated motor-respiratory coordination (MRC) in visually guided forearm tracking movements focusing on two main questions: (1) Does attentional demand, training or complexity of the tracking task have an effect on the degree of MRC? (2) Does MRC impair the precision of those movements? We hypothesized that (1) enhanced attention to the tracking task and training increase the degree of MRC while higher task complexity would reduce it, and (2) MRC impairs tracking precision. Methods: Thirty-five volunteers performed eight tracking trials with several conditions: positive (direct) signal–response relation (SRR), negative (inverse) SRR to increase task complexity, specific instruction for enhanced attention to maximize tracking precision (“strict” instruction), and specific instruction that tracking precision would not be evaluated (“relaxed” instruction). The trials with positive and negative SRR were performed three times each to study training effects. Results: While the degree of MRC remained in the same range throughout all experimental conditions, a switch in phase-coupling pattern was observed. In conditions with positive SRR or with relaxed instruction, we found one preferred phase-relationship per period. With higher task complexity (negative SRR) or increased attentional demand (strict instruction), a tighter coupling pattern with two preferred phase-relationships per period was adopted. Our main result was that MRC improved tracking precision in all conditions except for that with relaxed instruction. Reduction of amplitude errors mainly contributed to this precision improvement. Conclusion: These results suggest that attention devoted to a precision movement intensifies its phase-coupling with breathing and enhances MRC-related improvement of tracking precision.