Exercise Induced Muscle Damage
Exercise Induced Muscle Damage (EIMD)[edit | edit source]
EIMD arises when muscles become damaged after exercise. This often occurs when an athlete participates in a new or unfamiliar exercise, when learning new techniques, or experiences an increase in the volume or intensity of exercise. This can lead to short term performance decrements due to changes in the make-up of the muscles. These performance decrements are commonly caused by an increase in resting energy expenditure and metabolic demand, a decrease in the strength and power output the muscles can produce, and the athletes perception of the muscle soreness. The main effects of EIMD commonly arise 24-48 hours after muscle damage occurs.
Mechanism[edit | edit source]
EIMD has been a topic of intense focus in exercise and sports science research for more than 30 yr. It is a condition characterised by transient ultrastructural myofibrillar disruption, loss of muscle strength and power, delayed onset muscle soreness (DOMS), swelling, reduced range of motion of the affected limb, increased release of muscle proteins into the interstitial space, and circulation and a rise in muscle temperature.
Image 2: Skeletal muscle
It is understood that EIMD and the recovery is slower after eccentric (i.e., lengthening) vs. concentric (i.e., shortening) muscle contractions. Concentric muscle contractions do not cause exercise-induced muscle damage, but exercise-induced muscle damage is evident after isometric contractions at a long muscle length and eccentric muscle contractions, even at low intensity.
Image 3: Sarcomere
Various mechanisms likely account for the loss of strength after eccentrically biased exercise, which is considered to be the best indicator of exercise-induced muscle damage. These mechanisms are outlined in the following theoretical model.
- Mechanical strain during eccentric exercise causes one-half sarcomere nonuniformity and overstretching of sarcomeres beyond filament overlap, leading to “popped sarcomeres.” The Sarcomere is the name given to the part of the muscle fibre that contracts.
- These alterations likely directly reduce force production and overload sarcolemma and t-tubule structures. In turn, these events cause opening of stretch-activated channels, membrane disruption, and excitation-contraction coupling dysfunction.
- Ca2+ entering the cytosol through stretch-activated channels and/or permeable sections of the sarcolemma may stimulate calpain enzymes to degrade contractile proteins or excitation-contraction coupling proteins, resulting in prolonged loss of muscle strength.
The muscle adapts rapidly to the structural damage caused by exercise, and further soreness and damage in later exercise events is mitigated.
Satellite Cells in EIMD[edit | edit source]
Satellite cells (SC) play an integral role in the recovery from skeletal muscle damage and supporting muscle hypertrophy. Satellite cells are activated through various signaling pathways as a response to exercise.
Image 4: Myogenesis Schematic of satellite cell myogenesis and markers typical of each stage
- SC responses to acute and chronic resistance exercise are similar in males and females and SC and myonuclear accretion is related to training-induced muscle fiber hypertrophy.
- Regeneration of skeletal muscle is a highly synchronized process that requires muscle stem cells (satellite cells).
New research however (2021)study found that localized injuries, as experienced through exercise, activates a myofiber self-repair mechanism that is independent of satellite cells..
Physiotherapy Implications[edit | edit source]
EIMD can have a detrimental effect on performance eg
- Endurance cyclists demonstrating decreases in power output during race situations
- Marathon runners and down hill runners muscle fibers reveal remarkable damage after both training and marathon competition
Image 5: Changes in muscle thickness following exercise-induced muscle damage.
The largest deficits in strength, speed and agility have all been found 48 hours after muscle damage occurred. Within sport these margins can have a significant effect on the competition outcome.
- When muscle strength decreases by ≤20% immediately after exercise, it is usually restored within 2 days after exercise.
- When muscle strength decreases by ∼50% immediately after exercise, especially for the initial exposure to eccentric muscle contractions, it remains below pre-exercise values at 7 days after exercise.
In some instances EIMD may be beneficial because it can increase muscle hypertrophy (an increase in muscle mass). This happens as the small tears in the muscle tissues release muscle proteins that are used in generating new muscle cells.
The risk of EIMD can be reduced by avoiding new training techniques and increases in volume and intensities of exercise within 14 days of competition. This is particularly important if introducing exercises with high eccentric components such as plyometrics and Olympic Weightlifting.
When athletes are experiencing EIMD it is essential to maximize the recovery interventions. It is possible that training during EIMD may not affect performance, however it may delay recovery. This must be taken into account if the athlete is preparing for an upcoming competition.
There is a large interindividual variability of the responses to EIMD. The “repeated bout effect,” may protect athletes from EIMD, that is, after a first session of damaging exercise, skeletal muscle tissue adapts and is less vulnerable to injury in subsequent sessions of the same type of exercise. In fact, it has been shown that repetition of a damaging exercise results in less EIMD, inflammation, oxidative stress, leukocyte infiltration, and strength loss .
Treatment for EIDM
Many treatments have been tested to determine whether they help to restore muscle function and reduce muscle soreness following exercise. Perhaps with the exception of massage, cold water immersion, and wearing compression garments, these treatments have not produced consistent benefits. Although evidence is lacking to support the physical benefits of some of these treatments, their perceptual effects may be important for exercise recovery. In this regard, however, a key consideration is whether by masking the perception of pain or accelerating recovery ahead of structural remodeling, some of these treatments may actually increase risk of further muscle injury.
References[edit | edit source]
- Sports Science for Coaches Exercise Induced Muscle Damage Available: https://sportsscienceforcoaches.wordpress.com/2015/01/25/exercise-induced-muscle-damage/(accessed 22.11.202)
- Fatouros IG, Jamurtas AZ. Insights into the molecular etiology of exercise-induced inflammation: opportunities for optimizing performance. Journal of inflammation research. 2016;9:175.Available:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5085309/ (accessed 23.11.2021)
- Peake JM, Neubauer O, Della Gatta PA, Nosaka K. Muscle damage and inflammation during recovery from exercise. Journal of applied physiology. 2017 Mar 1;122(3):559-70.Available:https://journals.physiology.org/doi/full/10.1152/japplphysiol.00971.2016 (accessed 22.11.2021)
- Lumen learning EIMD Available: https://courses.lumenlearning.com/fitness/chapter/exercise-induced-muscle-damage/ (accessed 22.11.2021)
- Abou Sawan S, Hodson N, Babits P, Malowany JM, Kumbhare D, Moore DR. Satellite cell and myonuclear accretion is related to training-induced skeletal muscle fiber hypertrophy in young males and females. Journal of Applied Physiology. 2021 Sep 1;131(3):871-80.Available:https://pubmed.ncbi.nlm.nih.gov/34264129/ (accessed 22.11.2021)
- Roman W, Pinheiro H, Pimentel MR, Segalés J, Oliveira LM, García-Domínguez E, Gómez-Cabrera MC, Serrano AL, Gomes ER, Muñoz-Cánoves P. Muscle repair after physiological damage relies on nuclear migration for cellular reconstruction. Science. 2021 Oct 15;374(6565):355-9.Available: https://www.science.org/doi/pdf/10.1126/science.abe5620?download=true(accessed 22.11.2021)