Protein Supplementation and Skeletal Muscle Healing Process

Study Overview
=================
Brief Summary
-----------------
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.

Detailed Description
-----------------
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.

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

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

Intervention / Treatment
-----------------
* Dietary Supplement: Milk protein isolate
* Dietary Supplement: Placebo


Participation Criteria
=================
Eligibility Criteria
-----------------
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

Ages Eligible for Study
-----------------
Minimum Age: 18 Years
Maximum Age: 30 Years

Sexes Eligible for Study
-----------------
Male

Accepts Healthy Volunteers
-----------------
Accepts Healthy Volunteers

Study Plan
=================
How is the study designed?
-----------------

Design Details

Primary Purpose: Basic Science
Allocation: Randomized
Intervention Model: Crossover Assignment
Masking: Double


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: Protein<br>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. | Dietary Supplement: Milk protein isolate<br>* 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.<br>|
| Active Comparator: Placebo<br>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. | Dietary Supplement: Placebo<br>* 500 mL drink that contained water (375 mL), sugar-free cordial (125 mL) and 2 g of low-calorie glucose/dextrose powder.<br>|

What is the study measuring?
-----------------
Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Change in reduced glutathione in blood | Concentration of reduced glutathione in red blood cells | 1h before exercise, 2h post-exercise, daily for 8 days post-exercise | 
| Change in protein carbonyls in serum | Concentration of protein carbonyls | 1h before exercise, 2h post-exercise, daily for 8 days post-exercise | 
| Change in protein carbonyls in muscle | Protein carbonyl concentration in quadriceps skeletal muscle group | 1h before exercise, 2 days post-exercise, 8 days post-exercise | 
| Change in thiobarbituric acid and reactive substances in serum | Thiobarbituric acid reactive substances concentration in serum | 1h before exercise, 2h post-exercise, daily for 8 days post-exercise | 
| Change in oxidized glutathione in blood | Concentration of oxidized glutathione in red blood cells | 1h before exercise, 2h post-exercise, daily for 8 days post-exercise | 
| Change in total antioxidant capacity in serum | Total antioxidant capacity in serum | 1h before exercise, 2h post-exercise, daily for 8 days post-exercise | 
| Change in catalase activity in serum | Catalase activity in serum | 1h before exercise, 2h post-exercise, daily for 8 days post-exercise | 
| Change in creatine kinase activity in plasma |  | 1h before exercise, 2h post-exercise, daily for 8 days post-exercise | 
| Change in C-reactive protein in plasma |  | 1h before exercise, 2h post-exercise, daily for 8 days post-exercise | 
| Change in white blood cell count in blood |  | 1h before exercise, 2h post-exercise, daily for 8 days post-exercise | 
| Changes in volume and morphological complexity of immune cells |  | 1h before exercise, 2h post-exercise, daily for 8 days post-exercise | 
| Change in neutrophil count in blood |  | 1h before exercise, 2h post-exercise, daily for 8 days post-exercise | 
| Change in glucose concentration in blood |  | 1h before exercise, 2h post-exercise, daily for 8 days post-exercise | 
| Change in insulin concentration in blood |  | 1h before exercise, 2h post-exercise, daily for 8 days post-exercise | 
| Change in testosterone concentration in plasma |  | 1h before exercise, 2h post-exercise, daily for 8 days post-exercise | 
| Change in cytokine concentration in plasma | Measurement of IL-1β, IL-4, IL-6, IL-8, IL-10, TNF-α | 1h before exercise, 2h post-exercise, daily for 8 days post-exercise | 
| Change in adhesion molecule concentration in blood |  | 1h before exercise, 2h post-exercise, daily for 8 days post-exercise | 
| Change in intracellular signalling proteins in muscle | 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. | 1h before exercise, 2 days post-exercise, 8 days post-exercise | 
| Change in proteasome activities in muscle | Measurement of LLVY, LSTR and LLE | 1h before exercise, 2 days post-exercise, 8 days post-exercise | 
| Change in protein expression level of proteasome subunits | Measurement of B1i, B2i, B5i, B5, B1, B2 and α7 | 1h before exercise, 2 days post-exercise, 8 days post-exercise | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Change in muscle function of knee extensor and flexor muscle | Assessment of muscle peak and mean torque of knee extensors and flexors on an isokinetic dynamometer at 0, 90 and 180 degrees/sec | 1h before exercise, 5 min post-exercise, 2h post-exercise, daily for 8 days post-exercise | 
| Body composition | Assessment of percent (%) body mass | One day before exercise | 
| Maximal aerobic capacity | Assessment of maximal oxygen consumption | One day before exercise | 
| Change in dietary intake profile | Assessment of dietary intake with emphasis on protein consumption | 1h before exercise, daily for 8 days post-exercise |