Impact of Rest Duration on Achilles Tendon Structure and Function Following Isometric Training

Authors

Waugh CM, Alktebi T, de Sa A, Scott A

Publisher

Scand J Med Sci Sports 2017 June 12.

Publishing detail

PMID: 28603874

The Role of Rest Duration in Achilles Tendon Adaptation: Insights from a 12-Week Training Study

Achilles tendon (AT) injuries are common, especially among athletes, due to the high mechanical demands placed on this crucial structure. With intervention programs targeting AT strengthening, recent research has focused on the role of rest duration between exercises, hypothesizing that varying rest durations could influence collagen synthesis, thus enhancing tendon adaptation. The study, authored by Waugh, Alktebi, de Sa, and Scott and published in the Scandinavian Journal of Medicine & Science in Sports (2017), dives deep into the effects of different rest durations on AT structure and function.

Study Design: Comparing Long and Short Rest Intervals

The study involved 14 adults participating in a 12-week progressive isometric training program. Each training session included five sets of 10 plantarflexion contractions, each held for 3 seconds at 90% of maximum voluntary contraction (MVC). Sessions took place three times weekly, with one leg of each participant randomly assigned to a long rest training (LRT) protocol (10 seconds of rest between contractions) and the other to a short rest training (SRT) protocol (3 seconds of rest).

Researchers hypothesized that the leg trained under the LRT protocol would show improved AT collagen organization due to the extended rest periods allowing greater collagen synthesis by tenocytes, potentially leading to improved tendon biomechanical function.

Key Findings: Rest Duration’s Impact on Tendon Collagen

The study used ultrasound tissue characterization (UTC) to assess changes in collagen organization and morphology, providing a direct look at the tendon’s structural adaptations over the training period. Contrary to initial expectations, neither protocol led to a measurable improvement in collagen organization. Surprisingly, an unexpected decrease in the proportion of echotype I (indicating organized collagen) was observed in the SRT group (P<.001), while the LRT group showed no such reduction (P=.58). These findings suggest that longer rest intervals may have a protective effect on collagen structure during isometric loading.

Functional Adaptations: Strength Gains and Biomechanical Response

Despite the lack of improvement in collagen organization, both the LRT and SRT protocols were equally effective at enhancing Achilles tendon strength and mechanical properties. Significant strength gains were observed across both protocols (P≤.001), pointing to the effectiveness of isometric training in improving tendon resilience regardless of rest duration.

Implications for Rehabilitation and Injury Prevention

This study underscores the importance of considering rest duration in tendon rehabilitation and injury prevention programs. While collagen organization did not improve as hypothesized, the protective effect observed with longer rest intervals could be critical in designing interventions that prevent tendon degeneration over time. Further research is recommended to determine the optimal loading patterns and rest durations that best promote tendon adaptation without compromising structural integrity.

By exploring the nuances of rest intervals and their impact on tendon structure and function, this study provides a foundation for more refined approaches to Achilles tendon training and injury management.