Abstract
This study examined whey protein isolate supplementation combined with endurance training on cycling performance, aerobic fitness and immune cell responses. Eighteen male cyclists were randomly assigned to either placebo (PLA) or whey protein supplementation (WS; 1.0 g·kg body mass−1·d−1 in addition to their dietary intake). Both groups completed the identical endurance training program, 4 days per week for 6 weeks. Blood samples were obtained at rest and after 5 and 60 min of recovery from a simulated 40 km cycling time trial (TT) and were repeated after training. Baseline dietary intake of protein prior to supplementation was 1.52 ± 0.45 and 1.46 ± 0.44 g·kg body mass−1·d−1 for the WS and PLA groups, respectively. There were similar improvements in TT performance (WS: 71.47 ± 12.17 to 64.38 ± 8.09 min; PLA: 72.33 ± 12.79 to 61.13 ± 8.97 min), and peak oxygen uptake (WS: 52.3 ± 6.1 to 56.1 ± 5.4 mL·kg−1·min−1; PLA: 50.0 ± 7.1 to 54.9 ± 5.1 mL·kg−1·min−1) after training in both groups. White blood cells (WBC) and neutrophil counts were elevated 5 min after the TT and further increased after 60 min (P < 0.05). The exercise-induced increase in WBC and neutrophil counts at 5 and 60 min after the TT were attenuated after training compared to before training (P < 0.05). Lymphocytes increased 5 min after the TT and decreased below rest after 60 min of recovery (P < 0.05). Following training lymphocytes were lower after 60 min of recovery compared to before training. There was no change in natural killer cell activity with exercise, training or between groups. It was concluded that whey protein isolate supplementation while endurance training did not differentially change cycling performance or the immune response at rest or after exercise. However, endurance training did alter performance, aerobic fitness and some post exercise immune cell counts.
Highlights
Protein is an integral part of any diet but it is especially important for athletes [1, 2]
Protein supplementation [provided during exercise (38 ± 4 g of protein) and after exercise (29 ± 5 g of protein) for a total protein intake of 184 ± 44 g·d−1 or 2.6 g·kg−1·d−1 compared to an iso-caloric carbohydrate group whom was provided no protein during or immediately after exercise and ingested 120 ± 38 g of protein·d−1 or 1.7 g of protein·kg−1·d−1] during a 10-day intensified training period did not enhance 30 km cycling time trial performance [10]
The purpose of this study was to examine the effect of whey protein isolate supplementation in addition to the athlete’s habitual dietary protein intake combined with endurance training on cycling performance, cardio-respiratory fitness, as well as resting and post exercise immune cell responses
Summary
Protein is an integral part of any diet but it is especially important for athletes [1, 2]. Protein supplementation [provided during exercise (38 ± 4 g of protein) and after exercise (29 ± 5 g of protein) for a total protein intake of 184 ± 44 g·d−1 or 2.6 g·kg−1·d−1 compared to an iso-caloric carbohydrate group whom was provided no protein during or immediately after exercise and ingested 120 ± 38 g of protein·d−1 or 1.7 g of protein·kg−1·d−1] during a 10-day intensified training period did not enhance 30 km cycling time trial performance [10]. Ferguson-Stegall et al [12] and Robinson et al [13] found that protein supplementation following endurance training for 4 and 6 weeks, respectively, enhanced whole body oxygen uptake compared to post exercise iso-caloric carbohydrate supplementation. It is notable that the later study was performed in older, untrained individuals, and the literature has shown that older individuals experience a reduced anabolic response to protein compared to younger individuals [14]
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