Author(s): HANSELL, E., THORLEY, J., REYNOLDS, K.M., ŠKARABOT, J., JAMES, L.J., CLIFFORD, T., Institution: LOUGHBOROUGH UNIVERSITY, Country: UNITED KINGDOM, Abstract-ID: 1719

INTRODUCTION:
(Poly)phenols may mitigate exercise-induced muscle damage (EIMD), ostensibly due to their antioxidant and anti-inflammatory properties. However, such research is limited to high doses of (poly)phenols in singular foods or compounds, such as tart cherry juice or curcumin. Indeed, there is a paucity of research on whether interventions containing a range of (poly)phenolic foods can attenuate symptoms of EIMD, such as muscle function loss, and delayed onset of muscle soreness (DOMS). Providing a range of (poly)phenol-rich foods could elicit synergistic effects, enhancing the efficacy of (poly)phenol interventions, and offer an alternative to concentrated supplements. Thus, the aim of this study was to examine whether a (poly)phenol-rich diet could attenuate markers of EIMD.
METHODS:
Thirty (n=18 males, n=12 females) recreationally strength trained individuals (age 23±3 y; height 1.74±0.11 m; mass 71.3±11.5 kg) were randomly assigned to a (poly)phenol unrestricted (U-POL) or (poly)phenol restricted (R-POL) diet for 10 days. The U-POL diet was further supplemented with high (poly)phenol foods (40 g/day of dark chocolate and walnuts) and the R-POL diet with low (poly)phenol foods (40 g/day of milk chocolate and peanuts). On day 8 of their diet, participants completed 200 eccentric knee extensions at 60°s-1 on an isokinetic dynamometer. Pre (PRE), post (POST), 24 h-post (24H), 48 h-post (48H), and 72 h-post-exercise (72H), maximum isometric voluntary force of the knee extensors (MIVF), DOMS (0-200mm VAS), and via femoral nerve stimulation, voluntary activation (VA), rate of twitch development within 0-50 ms (RTD.50), time to peak twitch (CT), and half relaxation time (0.5RT) were assessed. At PRE, POST and 48H, white blood cell (WBC), neutrophil (NEU), and lymphocyte (LYM) counts were measured. Mixed-model ANOVAs were used to examine for group x time-point interactions; Bonferroni adjustments were applied for post-hoc tests.
RESULTS:
Energy intake, macronutrient intake, and total work completed during exercise did not differ between groups (P≥0.293). The U-POL group consumed more (poly)phenol-rich foods in total than the R-POL group (+322 g/day; P<0.001), including more fruits, vegetables, herbs and spices (+158 g/day; P<0.001), and wholegrains (+69 g/day; P=0.004). MIVF was reduced by ~31% post-exercise and remained ~12% below baseline at 72H (P<0.001). Exercise increased DOMS, which peaked at 48H (+148%; P<0.001). VA, CT, RTD.50, and 0.5RT were reduced at POST (P≤0.019), and at 24H for VA and RTD.50 (P≤0.043). NEU were elevated at POST (P<0.001), and LYM were reduced at POST and 48H (P<0.001). No significant group (P≥0.432) or interaction (P≥0.160) effects were observed for any variable.
CONCLUSION:
A (poly)phenol-rich diet for 10 days did not significantly influence MIVF, DOMS, neuromuscular function, or WBC counts in the 72-h following 200 eccentric muscle contractions, possibly due to an insufficient dose and/or the inherent inter-individual variability in EIMD responses.