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.

Impact of cow’s milk intake on exercise performance and recovery of muscle function: a systematic review

“…No other effects were observed.Cockburn et al [31]24 (males)21 ± 3Regularly competed in team sports (football, rugby, hockey and cricket)Between-group design● Cow’s semiskimmed milk (1.7%)● Low-fat chocolate milk● Carbohydrate beverage● Placebo beverage (water)Exercise inducing muscle damage in the hamstrings using isokinetic dynamometry (6 sets of 10 repetitions, eccentric and concentric contractions, with 90 s of rest between sets) at a speed of 1.05 rad/s500 mL on two occasions, immediately after and within 2 h after the exercise (total volume: 1000 mL). The volume of placebo was similar to the intervention onei) peak torque of the best repetition (dominant leg); ii) CK; iii) Mb; iv) passive and active VAS muscle soreness● Cow’s milk attenuated the decrements (48 h) in total work of the set, peak torque, CK and Mb after a bout of exercise-induced muscle damage.● The muscle soreness assessed using VAS was similar between the groups.Kirk et al [33]21 (males)23 ± 3Regularly competed in team sports (Gaelic football, soccer, rugby)Between-group design● A2 milk● Regular milk (cow’s milk)● Placebo beverage (maltodextrin mixed with water)Repeated sprint protocol (15 × 30 m sprints with 60 s of rest between series)500 mL immediately after the exercise. The volume of placebo was similar to the intervention onei) CMJ; ii) MVCs; iii) 20-m sprint test; iv) VAS muscle soreness● CMJ recovered quicker in both cow’s milk groups vs. the placebo group.…”

“…All the included studies used cow’s milk products. A total of 7 studies (63.6%) investigated the acute effect of cow’s milk after resistance or high-intensity exercise [27–33], whereas three studies (27.3%) determined the acute effect of cow’s milk after endurance exercise [34–36]. In addition, one study [37] analyzed the long-term effect (over 12 weeks of resistance training) of exercise and cow’s milk on the maximum repetition strength of squat and bench press.

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“…The exercise performance outcomes measured were muscular strength related variables [27–33, 37]. Regarding muscle function recovery, most of the studies [27–33] determined muscle soreness or damage using subjective scales such as VAS, and the most of them added also measures of blood biomarkers (e.g., CK or myoglobin) [27–32].…”

“…Cow’s milk attenuated losses in peak torque (maximal effort concentric knee flexion) [27, 28, 30, 31], total work of the set (6 concentric knee flexion repetitions) using isokinetic dynamometry [31], countermovement jump [27, 28, 33], rate of force development of an isometric contraction of the dominant leg quadriceps [27, 28], and sprint tests [27, 29, 32]. On the other hand, other studies observed no effect of cow’s milk on sprint recovery [28, 33], countermovement jump [32], reactive strength index [32], and bench and squat maximum strength after an exercise intervention [37].…”

Is There a Promising Market for the A2 Milk? Analysis of Italian Consumer Preferences

“…Documents by year from Scopus and Science Direct database, using the keywords "β-casein" AND "milk". Some studies have reported health benefits from drinking A2 milk [5][6][7][8][9][10][11]; others show no evidence [12,13]. In addition, the European Food Safety Authority (EFSA) reviewed the scientific literature and published their results in 2009, finding that it could not be established that bioactive peptides in milk containing both the A1 and A2 proteins have an adverse effect on health.…”