Submaximal Eccentric Exercise Influences Muscle and Connective Tissue Stiffness and Microcirculation: Evaluating the Impact of Myofascial Release on Recovery

Eccentric exercise, compared to concentric exercise, leads to various physiological changes such as altered neuromotor strategies, actin-myosin interactions, and greater cortical activation, but often results in muscle damage and inflammation. The deep fascia, particularly the thoracolumbar fascia (TLF), plays a significant role in these processes, especially in delayed onset muscle soreness (DOMS). DOMS typically peaks 24 to 48 hours after eccentric exercise, presenting with pain and mechanical hyperalgesia. Traditional theories like sarcomere damage or lactate accumulation inadequately explain DOMS-related pain, prompting recent research into the role of the deep fascia.

The TLF, rich in nerves and blood vessels, contributes to passive spine stability and muscle force generation, and is implicated in low back pain due to densification and fibrosis. Swelling in the TLF can reduce blood flow, leading to inflammation, and may be alleviated by myofascial release (MFR) techniques, which improve blood flow and tissue shearing capacity.

Research shows that about one-third of muscle injuries involve fascial damage, often from excessive stretching during eccentric exercise, leading to swelling and increased DOMS. Swelling and stiffness of the TLF after maximal eccentric exercise have been confirmed. Impaired recruitment of the erector spinae muscle (ES) in DOMS can reduce movement control, necessitating therapeutic measures to counteract these effects.

In competitive sports, severe DOMS is less common due to regular training. Submaximal eccentric exercise, with minimal DOMS, better reflects competitive scenarios, though it still elicits different physiological responses compared to concentric exercise.

A study from Hamburg explores the effects of submaximal eccentric exercise on TLF and ES stiffening and microcirculation, and the impact of MFR.

Trial

This randomized, controlled trial explored the effects of submaximal eccentric trunk extension exercise, which does not cause delayed onset muscle soreness (DOMS), on pain, microcirculation, and stiffness of the extramuscular connective tissue (ECT) and erector spinae muscle. The study also examined the impact of myofascial release (MFR) by a therapist compared to a placebo (sham laser therapy). Participants were 21 healthy, trained individuals who regularly engaged in over four hours of exercise per week. The study measured the stiffness of the ECT and erector spinae muscle, microcirculation (using white light and laser Doppler spectroscopy), and pain (using a visual analogue scale and pressure pain threshold) before, 24 hours, and 48 hours after the exercise.

Results

The study found that while erector spinae muscle stiffness increased one and two days after exercise in both the myofascial release and placebo groups, extramuscular connective tissue stiffness remained unchanged. This contrasts with earlier research which showed changes in extramuscular connective tissue stiffness following maximal exercise. The results suggested that submaximal eccentric exercise might lead to different outcomes compared to maximal exercise, particularly in the absence of severe delayed onset muscle soreness.

Myofascial release reduced erector spinae muscle stiffness by 14% one day post-exercise, potentially due to changes in neuromuscular control influenced by fluid dynamics within the tissue. However, extramuscular connective tissue stiffness appeared unaffected by myofascial release, and the study noted large individual differences in response, suggesting complex underlying mechanisms not fully captured by the measurements used.

Blood flow and oxygenation dynamics also differed, with the myofascial release group showing lower hemoglobin levels two days post-exercise, potentially indicating improved blood outflow. Participants in the myofascial release group experienced a 30% higher pressure pain threshold two days after exercise compared to the placebo group, aligning with other studies that noted benefits of manual therapy post-exercise.

Overall, the study suggests a complex interplay between muscle-fascia dynamics and treatment effects, indicating the need for further research to clarify these relationships and optimize recovery strategies for athletes.

Overall, MFR seemed to positively influence pain management, microcirculation, and muscle stiffness following submaximal eccentric exercise, indicating potential benefits for recovery. Further research is needed to confirm these findings.