Whey Protein Supplementation Does Not Affect Vascular Measures Following Eccentric-induced Muscle Damage In Resistance-trained Individuals

PURPOSE: Due to a higher anti-inflammatory and antioxidant content, dairy products from pasture-raised grass-fed cows may modulate vascular tone to a greater extent compared to products from grain-fed cows. Since exercise-induced muscle damage (EIMD) can transiently disrupt vascular homeostasis, we tested the hypothesis that whey protein from pasture-raised grass-fed cows (PRWP) would enhance markers of vascular recovery compared to either conventional whey protein (CWP) or a non-protein control (NPC) following EIMD. METHODS: A 3-arm randomized, isocaloric placebo-controlled design was used to test 39 (26 male / 13 female) resistance-trained individuals (PRWP, n = 14; CWP, n = 12; NPC, n = 13). To induce EIMD, participants completed an eccentric barbell back squat protocol. Rested blood pressure and vascular assessments, including, augmentation index normalized to a heart rate of 75 bpm, subendocardial viability ratio, and pulse wave velocity via applanation tonometry, were performed post-EIMD (i.e., 24, 48, and 72 h into recovery). Participants consumed PRWP, CWP, or NPC three times daily throughout the recovery period. Linear mixed models with fixed factors for time, condition, and their interaction were used to determine the effect of supplementation on vascular recovery. Statistical significance was defined as a two-sided alpha of ≤0.05. RESULTS: Between-condition differences in blood pressure and vascular assessments were not observed at baseline (pre-EIMD). However, a significant interaction at 48 h post-EIMD was detected such that diastolic blood pressure was elevated in the PRWP condition (PRWP, 77 + 11 mm Hg; CWP, 66 + 9 mm Hg; NPC, 67 + 10 mm Hg; P = 0.011). Pulse wave velocity was not significantly different between groups (P = 0.598), visit (P = 0.753), or group by visit interaction (P = 0.418). No other differences in either blood pressure or vascular assessments were observed post-EIMD. CONCLUSIONS: In contrast to our hypotheses, a modest elevation in diastolic blood pressure was observed 48-h post-EIMD in the PRWP condition. The training history / status of our participant sample may have restricted the ability to detect EIMD-induced vascular perturbations.