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Eur J Appl Physiol DOI 10.1007/s00421-015-3290-x
ORIGINAL ARTICLE
The effects of beetroot juice supplementation on indices of muscle damage following eccentric exercise Tom Clifford1 · Oliver Bell1 · Daniel J. West1 · Glyn Howatson1,2 · Emma J. Stevenson1
Received: 10 August 2015 / Accepted: 26 October 2015 © Springer-Verlag Berlin Heidelberg 2015
Abstract Purpose 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 muscledamaging effects of eccentric exercise. Methods 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. Results 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 0.05). Conclusions Acute beetroot juice supplementation attenuated muscle soreness and decrements in CMJ performance induced by eccentric exercise; further research on the antiinflammatory effects of beetroot juice are required to elucidate the precise mechanisms. Keywords Exercise recovery · Muscle damage · Inflammation · Betalains
Introduction Eccentric muscle contractions are an inherent component of numerous sporting movements such as decelerating, sprinting, and jumping (Byrne et al. 2004), and are frequently performed as part of strength and conditioning programms to promote gains in muscle size and strength (Howatson and van Someren 2008). However, when unaccustomed, eccentric muscle contractions can cause structural damage to the muscle cell, precipitating a transient increase in muscle soreness and reduction in muscle function (Paulsen et al. 2012). Muscle damage is accompanied by an acute phase inflammatory response (Pizza et al. 2005). Typically, inflammatory cells such as leukocytes, growth factors and cytokines accumulate at the damaged site to repair the damaged tissue (Tidball 2005). The immediate response involves phagocytosis, in which leukocytes, predominantly neutrophils and macrophages (M1 phenotype), release cytotoxic (i.e. reactive oxygen species; ROS) and proteolytic molecules to remove damaged tissue (Chazaud et al.
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sodium nitrate for 7-day attenuated the increase in inflammatory mediators (myeloperoxidase and P-selectin) following small intestinal injury (Jadert et al. 2012). More recently, sodium nitrate treatment reduced the expression of several inflammatory cytokines in the skeletal muscle of older mice, effects that were associated with improved grip strength and run time to exhaustion over an 8-week period (Justice et al. 2015). Although the precise mechanisms of NO’s proposed anti-inflammatory effects remain to be fully elucidated, the aforementioned data support the notion that NO may play a role in inflammatory disorders. This raises the possibility that exogenous NO donors, like beetroot juice for example, could be helpful for protecting against the potentially harmful effects that inflammation could have on cell function. However, whether these effects translate to humans or are evident with shorter supplementation periods
