The effects of beetroot juice supplementation on indices of muscle damage following eccentric exercise

Tom Clifford, Oliver Bell, Daniel J. West, Glyn Howatson, Emma J. Stevenson

Foods rich in antioxidant and anti-inflammatory phytochemicals might attenuate skeletal muscle damage; thus, the present study investigated whether consuming an antioxidant rich beetroot juice would attenuate the muscle-damaging effects of eccentric exercise. Using a double blind, independent groups design, 30 recreationally active males were allocated to consume a high dose of beetroot juice (H-BT; 250 ml), a lower dose of beetroot juice (L-BT; 125 ml), or an isocaloric placebo (PLA; 250 ml) immediately (×3 servings), 24 (×2 servings) and 48 h (×2 servings) following completion of 100-drop jumps. Maximal isometric voluntary contractions (MIVC), countermovement jumps (CMJ), pressure pain threshold (PPT), creatine kinase (CK), interleukin-6 (IL-6), interleukin-8 (IL-8) and tumour necrosis factor-α (TNF-α) were measured pre, post, 2 (blood indices only), 24, 48 and 72 h following the drop jumps. CMJ performance recovered quicker (relative to baseline) in H-BT vs. PLA at 48 (91.7 ± 12.2 vs. 74.4 ± 17.3 %; P = 0.009, ES = 1.00) and 72 h postexercise (93.4 ± 7.7 vs. 86 ± 5.9 %; P = 0.046, ES = 1.25). PPT was greater in both the H-BT and L-BT vs. PLA at 24, 48 and 72 h postexercise (P < 0.001); PPT had returned to baseline in H-BT and L-BT at 72 h postexercise, but was still reduced in PLA (80.1 ± 28.9 % of baseline values). MIVC, CK, IL-6, TNF-α and IL-8 were unaffected by beetroot juice (P > 0.05). Acute beetroot juice supplementation attenuated muscle soreness and decrements in CMJ performance induced by eccentric exercise; further research on the anti-inflammatory effects of beetroot juice are required to elucidate the precise mechanisms.