Purpose: To investigate the impact of milk protein ingestion on resistance exercise-induced muscle damage in untrained males and females. Rationale: Unaccustomed resistance exercise can cause muscle damage, presenting as muscle soreness and reduced muscle function - such as loss of strength, power, and flexibility - for several days after the exercise bout. Therefore, individuals may require longer recovery periods before performing another exercise bout, and their performance may be impaired. Further, muscle soreness may reduce exercise compliance, particularly in novice individuals. Over time, this may compromise the gains in muscle mass and strength achieved through exercise training. Therefore, strategies to reduce the severity of exercise-induced muscle damage and/or to enhance post-exercise recovery processes are advantageous for exercising individuals. One such strategy is the consumption of dietary protein before or after muscle-damaging exercise, which has shown to alleviate muscle soreness, improve blood markers of muscle damage, and reduce the decline in maximal force and flexibility. In particular, consuming 20-gram doses of milk protein in the days after resistance exercise can improve the recovery time of muscle soreness and maximum force, and also lower levels of damage markers in the blood. However, most studies have been conducted with male participants who are well-trained in resistance exercise. It has been suggested that males and females respond differently to muscle damage, and therefore, this research aims to provide a sex comparison in the muscle damage response to an acute bout of resistance exercise with or without milk protein feeding. Therefore, 40 healthy, young (18-35 years) adults (20 males, 20 females) will be recruited to participate in this randomised controlled trial. Maximal leg strength and body composition (by dual-energy X-ray absorptiometry; DXA) will be conducted at baseline. In females, all primary outcome measures will be obtained during the late follicular phase of the menstrual cycle. Participants will then be randomised to a protein (dairy yoghurt) or placebo (oat-based yoghurt) dietary condition. Three weeks later, participants will complete a high-intensity resistance exercise session on leg extension and leg curl machines to induce muscle damage. Various measures of muscle damage (blood biomarkers, muscle soreness, flexibility, and swelling) will be obtained before, immediately after, and 24, 48, 72, and 168 h after the exercise protocol. The maximal strength test will be repeated 72 and 168 h after the exercise. Participants will consume the protein or placebo yoghurt 4 times per day (every 3-4 hours) on the day of the exercise bout and the following 3 days. Participants' habitual activity and dietary intake will be monitored and controlled throughout the study period. Expected outcome: It is expected that the resistance exercise protocol will induce muscle damage, which will be attenuated with the ingestion of milk protein. It cannot be ascertained whether males and females will have the same responses to the exercise or to protein ingestion.
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
BASIC_SCIENCE
Masking
TRIPLE
Enrollment
40
Acute leg-based resistance exercise bout performed at 80% 1RM (4 sets to volitional failure on leg extension and leg curl machines)
Durham University, Sports and Wellbeing Park
Durham, United Kingdom
RECRUITINGMaximal Voluntary Contraction at baseline
One-repetition maximum (1RM) test: leg extension and leg curl machines
Time frame: Baseline
Change from baseline Maximal Voluntary Contraction at 72-hours post-exercise
One-repetition maximum (1RM) test: leg extension and leg curl machines
Time frame: 72-hours after the exercise bout
Change from baseline Maximal Voluntary Contraction at 168-hours post-exercise
One-repetition maximum (1RM) test: leg extension and leg curl machines
Time frame: 168-hours after the exercise bout
Creatine kinase concentration at baseline
Serum concentration of creatine kinase from venous blood sampling
Time frame: Immediately pre-exercise
Change from baseline in Creatine Kinase concentration immediately post-exercise
Serum concentration of creatine kinase from venous blood sampling
Time frame: Immediately after the exercise bout
Change from baseline in Creatine Kinase concentration at 24-hours post-exercise
Serum concentration of creatine kinase from venous blood sampling
Time frame: 24-hours after the exercise bout
Change from baseline in Creatine Kinase concentration at 48-hours post-exercise
Serum concentration of creatine kinase from venous blood sampling
Time frame: 48-hours after the exercise bout
Change from baseline in Creatine Kinase concentration at 72-hours post-exercise
Serum concentration of creatine kinase from venous blood sampling
Time frame: 72-hours after the exercise bout
Change from baseline in Creatine Kinase concentration at 168-hours post-exercise
Serum concentration of creatine kinase from venous blood sampling
Time frame: 168-hours after the exercise bout
Interleukin-6 concentration at baseline
Serum concentration of Interleukin-6 from venous blood sampling
Time frame: Immediately pre-exercise
Change from baseline in Interleukin-6 concentration immediately post-exercise
Serum concentration of Interleukin-6 from venous blood sampling
Time frame: Immediately after the exercise bout
Change from baseline in Interleukin-6 concentration at 24-hours post-exercise
Serum concentration of Interleukin-6 from venous blood sampling
Time frame: 24-hours after the exercise bout
Change from baseline in Interleukin-6 concentration at 48-hours post-exercise
Serum concentration of Interleukin-6 from venous blood sampling
Time frame: 48-hours after the exercise bout
Change from baseline in Interleukin-6 concentration at 72-hours post-exercise
Serum concentration of Interleukin-6 from venous blood sampling
Time frame: 72-hours after the exercise bout
Change from baseline in Interleukin-6 concentration at 168-hours post-exercise
Serum concentration of Interleukin-6 from venous blood sampling
Time frame: 168-hours after the exercise bout
Muscle soreness (pressure algometry) at baseline
Self-perceived rating of muscle soreness with use of pressure algometry
Time frame: Immediately pre-exercise
Change in muscle soreness (pressure algometry) immediately post-exercise
Self-perceived rating of muscle soreness with use of pressure algometry
Time frame: Immediately after the exercise bout
Change in muscle soreness (pressure algometry) at 24-hours post-exercise
Self-perceived rating of muscle soreness with use of pressure algometry
Time frame: 24-hours after the exercise bout
Change in muscle soreness (pressure algometry) at 48-hours post-exercise
Self-perceived rating of muscle soreness with use of pressure algometry
Time frame: 48-hours after the exercise bout
Change in muscle soreness (pressure algometry) at 72-hours post-exercise
Self-perceived rating of muscle soreness with use of pressure algometry
Time frame: 72-hours after the exercise bout
Change in muscle soreness (pressure algometry) at 168-hours post-exercise
Self-perceived rating of muscle soreness with use of pressure algometry
Time frame: 168-hours after the exercise bout
Muscle soreness (VAS) at baseline
Self-perceived rating of muscle soreness while performing a bodyweight squat with use of a visual analogue scale
Time frame: Immediately pre-exercise
Change in muscle soreness (VAS) immediately post-exercise
Self-perceived rating of muscle soreness while performing a bodyweight squat with use of a visual analogue scale
Time frame: Immediately after the exercise bout
Change in muscle soreness (VAS) at 24-hours post-exercise
Self-perceived rating of muscle soreness while performing a bodyweight squat with use of a visual analogue scale
Time frame: 24-hours after the exercise bout
Change in muscle soreness (VAS) at 48-hours post-exercise
Self-perceived rating of muscle soreness while performing a bodyweight squat with use of a visual analogue scale
Time frame: 48-hours after the exercise bout
Change in muscle soreness (VAS) at 72-hours post-exercise
Self-perceived rating of muscle soreness while performing a bodyweight squat with use of a visual analogue scale
Time frame: 72-hours after the exercise bout
Change in muscle soreness (VAS) at 168-hours post-exercise
Self-perceived rating of muscle soreness while performing a bodyweight squat with use of a visual analogue scale
Time frame: 168-hours after the exercise bout
Range of motion at baseline
Flexibility of the exercised limb as determined by goniometry
Time frame: Immediately pre-exercise
Change in range of motion immediately post-exercise
Flexibility of the exercised limb as determined by goniometry
Time frame: Immediately after the exercise bout
Change in range of motion at 24-hours post-exercise
Flexibility of the exercised limb as determined by goniometry
Time frame: 24-hours after the exercise bout
Change in range of motion at 48-hours post-exercise
Flexibility of the exercised limb as determined by goniometry
Time frame: 48-hours after the exercise bout
Change in range of motion at 72-hours post-exercise
Flexibility of the exercised limb as determined by goniometry
Time frame: 72-hours after the exercise bout
Change in range of motion at 168-hours post-exercise
Flexibility of the exercised limb as determined by goniometry
Time frame: 168-hours after the exercise bout
Limb circumference at baseline
Measure of leg circumference with use of standard anthropometric tape to indicate muscle swelling
Time frame: Immediately pre-exercise
Change in limb circumference immediately post-exercise
Measure of leg circumference with use of standard anthropometric tape to indicate muscle swelling
Time frame: Immediately after the exercise bout
Change in limb circumference at 24-hours post-exercise
Measure of leg circumference with use of standard anthropometric tape to indicate muscle swelling
Time frame: 24-hours after the exercise bout
Change in limb circumference at 48-hours post-exercise
Measure of leg circumference with use of standard anthropometric tape to indicate muscle swelling
Time frame: 48-hours after the exercise bout
Change in limb circumference at 72-hours post-exercise
Measure of leg circumference with use of standard anthropometric tape to indicate muscle swelling
Time frame: 72-hours after the exercise bout
Change in limb circumference at 168-hours post-exercise
Measure of leg circumference with use of standard anthropometric tape to indicate muscle swelling
Time frame: 168-hours after the exercise bout
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