title: A2 Milk Enhances Dynamic Muscle Function Following Repeated Sprint Exercise, a Possible Ergogenic Aid for A1-Protein Intolerant Athletes?
abstract: Hyperaminoacidemia following ingestion of cows-milk may stimulate muscle anabolism and attenuate exercise-induced muscle damage (EIMD). However, as dairy-intolerant athletes do not obtain the reported benefits from milk-based products, A2 milk may offer a suitable alternative as it lacks the A1-protein. This study aimed to determine the effect of A2 milk on recovery from a sports-specific muscle damage model. Twenty-one male team sport players were allocated to three independent groups: A2 milk (n= 7), regular milk (n= 7), and placebo (PLA) (n= 7). Immediately following muscle-damaging exercise, participants consumed either A2 milk, regular milk or PLA (500 mL each). Visual analogue scale (muscle soreness), maximal voluntary isometric contraction (MVIC), countermovement jump (CMJ) and 20-m sprint were measured prior to and 24, 48, and 72 h post EIMD. At 48 h post-EIMD, CMJ and 20-m sprint recovered quicker in A2 (33.4 ± 6.6 and 3.3 ± 0.1, respectively) and regular milk (33.1 ± 7.1 and 3.3 ± 0.3, respectively) vs. PLA (29.2 ± 3.6 and 3.6 ± 0.3, respectively) (p< 0.05). Relative to baseline, decrements in 48 h CMJ and 20-m sprint were minimised in A2 (by 7.2 and 5.1%, respectively) and regular milk (by 6.3 and 5.2%, respectively) vs. PLA. There was a trend for milk treatments to attenuate decrements in MVIC, however statistical significance was not reached (p= 0.069). Milk treatments had no apparent effect on muscle soreness (p= 0.152). Following muscle-damaging exercise, ingestion of 500 mL of A2 or regular milk can limit decrements in dynamic muscle function in male athletes, thus hastening recovery and improving subsequent performance. The findings propose A2 milk as an ergogenic aid following EIMD, and may offer an alternative to athletes intolerant to the A1 protein.
authors.affiliation: School of Health Sciences, Liverpool Hope University, Hope Park, Liverpool L16 9JD, UK. kirkb@hope.ac.uk.
authors.forename: Ben
authors.initials: B
authors.lastname: Kirk
authors.affiliation: Department of Sport, Exercise & Rehabilitation, Northumbria University, Newcastle Upon Tyne NE1 8ST, UK. j.mitchell@nutritionsociety.org.
authors.forename: Jade
authors.initials: J
authors.lastname: Mitchell
authors.affiliation: School of Health Sciences, Liverpool Hope University, Hope Park, Liverpool L16 9JD, UK. jacksom1@hope.ac.uk.
authors.forename: Matthew
authors.initials: M
authors.lastname: Jackson
authors.affiliation: School of Health Sciences, Liverpool Hope University, Hope Park, Liverpool L16 9JD, UK. amirabf@hope.ac.uk.
authors.forename: Farzad
authors.initials: F
authors.lastname: Amirabdollahian
authors.affiliation: School of Health Sciences, Liverpool Hope University, Hope Park, Liverpool L16 9JD, UK. alizado@hope.ac.uk.
authors.forename: Omid
authors.initials: O
authors.lastname: Alizadehkhaiyat
authors.affiliation: Department of Sport, Exercise & Rehabilitation, Northumbria University, Newcastle Upon Tyne NE1 8ST, UK. tom.clifford@northumbria.ac.uk.
authors.forename: Tom
authors.initials: T
authors.lastname: Clifford
mesh_terms: D000328:Adult; D000818:Animals; D056352:Athletes; D054874:Athletic Performance; D002417:Cattle; D004040:Dietary Carbohydrates / Q000008:administration & dosage / Q000032:analysis; D004041:Dietary Fats / Q000008:administration & dosage / Q000032:analysis; D004044:Dietary Proteins / Q000008:administration & dosage / Q000032:analysis; D004311:Double-Blind Method; D006801:Humans; D007537:Isometric Contraction / Q000502:physiology; D008297:Male; D008892:Milk / Q000737:chemistry*; D008894:Milk Proteins / Q000008:administration & dosage*; D018482:Muscle, Skeletal / Q000378:metabolism*; D063806:Myalgia; D012420:Running; D064133:Sports Nutritional Physiological Phenomena; D055815:Young Adult
chemical_list: D004040:Dietary Carbohydrates; D004041:Dietary Fats; D004044:Dietary Proteins; D008894:Milk Proteins
keywords: A2 milk; exercise recovery; muscle damage; muscle function; team sports