Abstract
BackgroundThis study examined the effect of carbohydrate and whey protein supplements on recovery of neuromuscular function after prolonged load carriage.MethodsTen male participants (body mass: 81.5 ± 10.5 kg, age: 28 ± 9 years, O2max: 55.0 ± 5.5 ml·kg-1·min-1) completed three treadmill walking tests (2 hr, 6.5 km·h-1), carrying a 25 kg backpack consuming 500 ml of either: (1) Placebo (flavoured water) [PLA], (2) 6.4% Carbohydrate Solution [CHO] or (3) 7.0% Whey Protein Solution [PRO]. For three days after load carriage, participants consumed two 500 ml supplement boluses. Muscle performance was measured before and at 0, 24, 48 and 72 h after load carriage, during voluntary and electrically stimulated contractions.ResultsIsometric knee extension force decreased immediately after load carriage with no difference between conditions. During recovery, isometric force returned to pre-exercise values at 48 h for CHO and PRO but at 72 h for PLA. Voluntary activation decreased immediately after load carriage and returned to pre-exercise values at 24 h in all conditions (P = 0.086). During recovery, there were no differences between conditions for the change in isokinetic peak torque. Following reductions immediately after load carriage, knee extensor and flexor peak torque (60°·s-1) recovered to pre-exercise values at 72 h. Trunk extensor and flexor peak torque (15°·s-1) recovered to pre-exercise values at 24 h (P = 0.091) and 48 h (P = 0.177), respectively.ConclusionRecovery of neuromuscular function after prolonged load carriage is improved with either carbohydrate or whey protein supplementation for isometric contractions but not for isokinetic contractions.
Highlights
Load carriage is a common endurance exercise in occupational settings (e. g. military services) that causes neuromuscular impairment of the shoulders, trunk and lower limbs [1] and muscle soreness [2]
There were no differences in pre-exercise values for muscle force or torque of a specific muscle group between conditions suggesting the absence of muscle fatigue and/or injury before each bout of load carriage
Force decreased from pre-exercise value immediately after load carriage for placebo beverage (PLA) (14 ± 7%, P < 0.001), CHO (12 ± 10%, P = 0.006) and protein (7%) beverage (PRO) (14 ± 8%, P < 0.001), with no difference between conditions (P > 0.05)
Summary
Load carriage (i.e. transporting loads in backpacks) is a common endurance exercise in occupational settings (e. g. military services) that causes neuromuscular impairment of the shoulders, trunk and lower limbs [1] and muscle soreness [2]. Fast recovery of muscle function in the days after load carriage is important. Recent studies have investigated the effects of protein supplementation on recovery of muscle function after endurance exercise [4] and eccentric exercise [5]. Its benefits have been reported after resistance exercise [7], but as far as we know, the effects of whey protein on recovery of muscle function after load carriage has not been investigated. As far as we known, a comparison of carbohydrate vs protein supplement on recovery of muscle function after prolonged load carriage has not been investigated. This study examined the effect of carbohydrate and whey protein supplements on recovery of neuromuscular function after prolonged load carriage. Muscle performance was measured before and at 0, 24, 48 and 72 h after load carriage, during voluntary and electrically stimulated contractions
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