Quercetin supplementation increases muscle oxidative capacity and endurance in mice, but its ergogenic effect in humans has not been established. Our study investigates the effects of short-duration chronic quercetin supplementation on muscle oxidative capacity; metabolic, perceptual, and neuromuscular determinants of performance in prolonged exercise; and cycling performance in untrained men. Using a double-blind, pretest-posttest control group design, 30 recreationally active, but not endurance-trained, young men were randomly assigned to quercetin and placebo groups. A noninvasive measure of muscle oxidative capacity (phosphocreatine recovery rate using magnetic resonance spectroscopy), peak oxygen uptake (Vo(2peak)), metabolic and perceptual responses to submaximal exercise, work performed on a 10-min maximal-effort cycling test following the submaximal cycling, and voluntary and electrically evoked strength loss following cycling were measured before and after 7-16 days of supplementation with 1 g/day of quercetin in a sports hydration beverage or a placebo beverage. Pretreatment-to-posttreatment changes in phosphocreatine recovery time constant, Vo(2peak,) substrate utilization, and perception of effort during submaximal exercise, total work done during the 10-min maximal effort cycling trial, and voluntary and electrically evoked strength loss were not significantly different (P > 0.05) in the quercetin and placebo groups. Short duration, chronic dietary quercetin supplementation in untrained men does not improve muscle oxidative capacity; metabolic, neuromuscular and perceptual determinants of performance in prolonged exercise; or cycling performance. The null findings indicate that metabolic and physical performance consequences of quercetin supplementation observed in mice should not be generalized to humans.

1) for both women and men, there is a positive association between the intensity of eccentric exercise performed with the elbow flexors and RPE; 2) perceived exertion ratings increase significantly then plateau when repeated eccentric muscle actions are performed at constant, submaximal absolute intensities; 3) women rate eccentric exercise performed at the same intensity (relativized to MVC-C) as being less effortful compared with men; and 4) RPE during eccentric exercise can account for a small but significant amount of variability in delayed-onset muscle pain after statistically controlling for differences in strength or relative intensity.

The exacerbation of musculoskeletal pain by stress in humans is modeled by the musculoskeletal hyperalgesia in rodents following a forced swim. We hypothesized that stress-sensitive corticotropin releasing factor (CRF) receptors and transient receptor vanilloid 1 (TRPV1) receptors are responsible for the swim stress-induced musculoskeletal hyperalgesia. We confirmed that a cold swim (26°C) caused a transient, morphine-sensitive decrease in grip force responses reflecting musculoskeletal hyperalgesia in mice. Pretreatment with the CRF2 receptor antagonist astressin 2B, but not the CRF1 receptor antagonist NBI-35965, attenuated this hyperalgesia. Desensitizing the TRPV1 receptor centrally or peripherally using desensitizing doses of resiniferatoxin (RTX) failed to prevent the musculoskeletal hyperalgesia produced by cold swim. SB-366791, a TRPV1 antagonist, also failed to influence swim-induced hyperalgesia. Together these data indicate that swim stress-induced musculoskeletal hyperalgesia is mediated, in part, by CRF2 receptors but is independent of the TRPV1 receptor.

The day-to-day reliability of lower leg volume is poorly documented. This investigation determined the day-to-day reliability of lower leg volume (soleus and gastrocnemius) measured using water displacement. Thirty young adults (15 men and 15 women) had their right lower leg volume measured by water displacement on five separate occasions. The participants performed normal activities of daily living and were measured at the same time of day after being seated for 30 min. The results revealed a high day-to-day reliability for lower leg volume. The mean percentage change in lower leg volume across days compared to day 1 ranged between 0 and 0.37%. The mean within subjects coefficient of variation in lower leg volume was 0.72% and the coefficient of variation for the entire sample across days ranged from 5.66 to 6.32%. A two way mixed model intraclass correlation (30 subjects x 5 days) showed that the lower leg volume measurement was highly reliable (ICC = 0.972). Foot and total lower leg volumes showed similarly high reliability. Water displacement offers a cost effective and reliable solution for the measurement of lower leg edema across days.

Fibromyalgia syndrome is characterized by widespread pain that is exacerbated by cold and stress but relieved by warmth. We review the points along thermal and pain pathways where temperature may influence pain. We also present evidence addressing the possibility that brown adipose tissue activity is linked to the pain of fibromyalgia given that cold initiates thermogenesis in brown adipose tissue via adrenergic activity, while warmth suspends thermogenesis. Although females have a higher incidence of fibromyalgia as well as more resting thermogenesis, they are less able to recruit brown adipose tissue in response to chronic stress than males. In addition, conditions that are frequently comorbid with fibromyalgia compromise brown adipose activity making it less responsive to sympathetic stimulation. This results in lower body temperatures, lower metabolic rates, and lower circulating cortisol/corticosterone in response to stress - characteristics of fibromyalgia. In the periphery, sympathetic nerves to brown adipose also project to surrounding tissues, including tender points characterizing fibromyalgia. As a result, the musculoskeletal hyperalgesia associated with conditions like fibromyalgia may result from referred pain in the adjacent muscle and skin.