Protein Supplementation and Skeletal Muscle Healing Process

Effects of Protein Supplementation on Skeletal Muscle Regeneration and Healing Process Following Exercise-induced Aseptic Injury

In this study the investigators utilized protein supplementation over an 8-day period following eccentric exercise-induced muscle damage in order to test the initial hypotheses : i) protein supplementation after exercise-induced muscle injury affects exercise-induced aseptic inflammation and muscle performance.

The objective was to examine weather protein supplementation is able to affect the inflammatory response as well as recovery of muscle performance following an intense eccentric exercise protocol. In a double-blind, counterbalanced design, 14 men received either Placebo (PLA) or milk protein isolate (PRO) for 8 consecutive days following a single bout of exercise (300 eccentric contractions at 30 deg/sec). In both conditions, performance was assessed at baseline, immediately post-exercise, 2h post-exercise and daily for 8 consecutive days. Blood samples were collected at baseline, 2h post-exercise and daily for the remaining 8 days. Muscle biopsies from vastus lateralis were collected at baseline as well as at day 2 and day 8 of the post-exercise period.

Skeletal Muscle Damage, Exercise-induced Aseptic Inflammation, Skeletal Muscle Performance, Intracellular Signaling in Skeletal Muscle, Proteasome Activation

Milk protein isolate supplementation: orally, 20g of protein immediately post-exercise and then 20g every 3h on 3 occasions (+3, +6, +9), on the exercise day. The remaining 8 days, 20g daily with breakfast.

Placebo administration: orally 500 ml, immediately post-exercise as well as at +3, +6 and +9 hours, on the exercise day. The remaining 8 days, 500 ml daily with breakfast.

Milk protein isolate in a powder form consisted of 80% casein and 20% whey protein. 20g were diluted into 500 ml water. Placebo consisted of 365 ml water, 125 ml sugar-free cordial and 2g of low-calorie glucose/dextrose powder.

500 mL drink that contained water (375 mL), sugar-free cordial (125 mL) and 2 g of low-calorie glucose/dextrose powder.

Measurement of phosphorylation levels of mammalian target of rapamycin (mTOR), ribosomal protein S6 (rpS6) and nuclear factor kB (NFkB), and protein expression levels of forkhead box protein O1 (FOXO1), HSP70, and parkin.

Assessment of muscle peak and mean torque of knee extensors and flexors on an isokinetic dynamometer at 0, 90 and 180 degrees/sec

Inclusion Criteria: a) recreationally trained as indicated by the maximal oxygen consumption levels (VO2max > 45 ml/kg/min), b) engaged in systematic exercise at least three times per week for > 12 months, c) non-smokers, d) abstained from any vigorous physical activity during the study, e) abstained from consumption of caffeine, alcohol, performance-enhancing or antioxidant supplements, and medications during the study. Exclusion Criteria: a) a recent febrile illness, b) history of muscle lesion, c) lower limb trauma

Exercise Biochemistry Laboratory, School of Physical Education & Sports Sciences, University of Thessaly