Research suggests that ingesting protein after resistance exercise (RE) increases muscle protein synthesis and results in greater muscle gains. The effect on energy expenditure and substrate utilization, however, is unclear. This study evaluated the effect of RE and post exercise protein on recovery energy expenditure and substrate utilization in 17 women (age 46.5 ± 1.2 y). A whey-protein supplement (120 kcal, 30 g protein) was ingested immediately after 1 bout of RE (PRO) and a non caloric placebo after another (PLA). VO2 and respiratory-exchange ratio (RER) were measured before and for 120 min after each exercise session. RE resulted in a significant increase in VO2 that persisted through 90 min of recovery (P < 0.01) and was not affected by protein supplementation. RE significantly lowered RER, resulting in an increase in fat oxidation for both PLA and PRO (P < 0.01). For PRO, however, RER returned to baseline values earlier than for PLA, resulting in a reduced fat-oxidation response (P = 0.02) and earlier return to pre exercise baseline values than for PLA. Substrate utilization was significantly different between conditions (P = 0.02), with fat contributing 77.76% ± 2.19% for PLA and 72.12% ± 2.17% for PRO, while protein oxidation increased from 17.18% ± 1.33% for PLA to 20.82% ± 1.47% for PRO. Post exercise protein did not affect energy expenditure, but when protein was available as an alternate fuel fat oxidation was diminished. Based on these findings it might be beneficial for middle-aged women to delay protein intake after RE to maximize fat utilization.
Melissa J. Benton and Pamela D. Swan
Melissa J. Benton, Maura C. Schlairet and David R. Gibson
To evaluate the effect of age on quality of life (QOL) in breast cancer survivors after resistance training, 20 women were assigned to 1 of 2 groups based on age (YRT 40–59 yr, ORT 60–80 yr). Both groups completed 3 sets of 8 exercises twice a week for 8 wk. Measurements were obtained before and after the training program. QOL was measured using the Body Image and Relationship Scale (BIRS). Both groups improved in chest press (p < .001), leg press (p < .001), arm curls (p < .05), and chair stands (p < .001). For QOL, YRT reported greater improvements compared with ORT in BIRS total score (Group × Time interaction, p = .002) and strength and health subscale score (Group × Time interaction, p = .001), and greater age was related to greater perceived impairment (BIRS total: r = .61, p = .004; strength and health subscale: r = .69, p = .001). Despite significant improvements in strength and function, older women perceived relatively little improvement in QOL compared with younger women, and age had a differential negative influence on improvements in QOL.