By Dr Stuart Galloway, Faculty of Health Sciences and Sport, University of Stirling. SCOTLAND; and Chair of the Sport and Exercise Nutrition register (SENr).
Introduction
Exercise-induced muscle damage leads to post-exercise reductions in muscle function, reduced range of motion, reduced force generating capacity, and increased muscle soreness. These symptoms are the result of ultrastructural damage to the tissue. This damage, and the repair process, are essential parts of the adaptive remodelling response to exercise training. Damage symptoms usually result from activity that is unaccustomed such as increases in training load, and are particularly evident when there has been an increase in eccentric loading of skeletal muscle. Muscle damage symptoms such as soreness typically peak between 24-48 hours after the unaccustomed activity has taken place. The duration of these symptoms depends upon the extent of damage and continued activities, but they usually resolve within 4-7 days. The symptom response and resolution time course is closely aligned to the inflammation response time course. Therefore, strategies adopted to reduce post-exercise muscle soreness have mostly targeted reduction of the inflammatory response. This is particularly true given that nociceptors within muscle have a hyperalgesic response to a wide variety of inflammatory markers through actions on surface receptors and ion channels. While excessive inflammation can be detrimental to repair / remodelling, strategies to reduce inflammation and the repair and remodelling process need careful consideration. For example, use of NSAID’s has been shown to reduce satellite cell proliferation and differentiation with implications for blunting the adaptive response of muscle to an exercise stimulus. Nutrition strategies targeting reduction of the symptoms of damage, or speed of repair / recovery have, therefore, been a focus of much research.
The research conducted over the past 50 years or so has examined a wide variety of potential food ingredients including:
- Protein, amino acids or creatine
- Phytochemicals (e.g. those present in pomegranate, pineapple, tart cherries, beetroot, and watermelon
- Omega-3 polyunsaturated fatty acids primarily from fish oils
- Curcumin (turmeric)
- Antioxidant vitamins
