Pathophysiology of exercise-induced muscle damage and its structural, functional, metabolic, and clinical consequences

Abstract

Extreme or unaccustomed eccentric exercise can cause exercise-induced muscle damage, characterized by structural changes involving sarcomere, cytoskeletal, and membrane damage, with an increased permeability of sarcolemma for proteins. From a functional point of view, disrupted force transmission, altered calcium homeostasis, disruption of excitation-contraction coupling, as well as metabolic changes bring about loss of strength. Importantly, the trauma also invokes an inflammatory response and clinically presents itself by swelling, decreased range of motion, increased passive tension, soreness, and a transient decrease in insulin sensitivity. While being damaging and influencing heavily the ability to perform repeated bouts of exercise, changes produced by exercise-induced muscle damage seem to play a crucial role in myofibrillar adaptation. Additionally, eccentric exercise yields greater hypertrophy than isometric or concentric contractions and requires less in terms of metabolic energy and cardiovascular stress, making it especially suitable for the elderly and people with chronic diseases. This review focuses on our current knowledge of the mechanisms underlying exercise-induced muscle damage, their dependence on genetic background, as well as their consequences at the structural, functional, metabolic, and clinical level. A comprehensive understanding of these is a prerequisite for proper inclusion of eccentric training in health promotion, rehabilitation, and performance enhancement.

Extreme duration exercise affects old and younger men differently

“… 60 The intervention had no effects on muscle fiber type composition and capillarization in either group, which was expected, given that the intervention was relatively short in duration and that the participants were very trained cyclists. Furthermore, given the fairly large daily protein intake (>2 g/kg body mass per day), where normal recommendations for intensive endurance training would be 1.6–1.8 g/kg body mass per day and the primarily concentric muscle use during cycling, 61 the intervention would not be expected to alter muscle fiber type/content. While small changes in fiber types have been documented in arm and leg muscle in response to extreme repeated prolonged exercise in cold temperatures for 4½ weeks, 62 the conditions of the intervention in the present study would not be expected to produce similar effects.…”

Using Shear-Wave Elastography to Assess Exercise-Induced Muscle Damage: A Review

“…Two studies [ 35 , 65 ] investigated HMB supplementation and reported that both 2-week and 4-week supplementation prior to elbow flexor eccentric exercise attenuated MVC and RoM loss, while the only effect on shear modulus was seen immediately post-exercise. While authors agree with the notion that Ca 2+ release during or following damage to the muscle membrane due to breakdown of the sarcomere causes an increase in shear modulus [ 6 , 11 ], further investigation would be needed to reveal why shear modulus was affected by HMB only immediately after the exercise, and to explain the discrepancy between shear modulus and RoM outcomes. The same research group also investigated fish oil supplementation and reported that it ameliorated the loss of MVC, RoM and also the increase in biceps brachii shear modulus [ 88 ].…”

“…While some degree of muscle damage and the associated inflammation are considered to be paramount for optimal muscle adaptation [ 3 , 4 ], excessive muscle damage impairs athletic performance and makes further training more difficult [ 5 ]. An abundant body of research exists on mechanisms underlying muscle damage and its manifestations [ 6 ], as well as prevention and treatment strategies [ 7 , 8 , 9 ].…”

Physical activity-correlated changes in plasma enzyme concentrations in fragile sarcolemmal muscular dystrophies

“…The sarcolemma experiences repeated and transient injuries by the normal stresses associated with physical activity 1 . In healthy individuals, the sarcolemma is repaired.…”

“…Damage to and subsequent necrosis of the muscle fiber allows release of muscle proteins into the extracellular environment 1, 2 . In the absence of inflammation, muscle-derived proteins move through interstitial fluid into the lymphatic system, where, as components of the lymph, these proteins are returned to blood.…”