Time of day and athlete status effects on the modified clinical test of sensory integration and balance (mCTSIB) and stability evaluation test (SET).

BACKGROUND: Concussions or musculoskeletal injuries may impair postural control, which is one diagnostic to help determine return-to-activity decisions. Postural control may be affected by diurnal rhythm. RESEARCH QUESTION: Does time of day influence postural control as measured by two Neurocom Balance Master diagnostic protocols, the Modified Clinical Test of Sensory Interaction on Balance (mCTSIB) and the Stability Evaluation Test (SET)? METHODS: Following Institutional Review Board (IRB) approval, consented participants completed the SET and mCTSIB twice: between 0700 and 1000; and between 1600 and 1900. We randomized and balanced testing order. Familiarization trials were completed for the mCTSIB and SET. Assessments were completed in a controlled laboratory environment. We instructed participants to get a normal night's sleep prior to testing and refrain from caffeine use and exhaustive exercise on the day of testing. Sixty-nine participants (48 female, 21 male: age = 21.42±2.56 years, height = 168.20±7.53 cm, mass = 72.05±16.60 kg) completed the study. Thirty-one of the participants were National Association of Intercollegiate Athletes (NAIA) student-athletes from the sports of baseball, soccer and softball. Average postural sway velocity was measured and compared by time of day for each of the balance conditions in the mCTSIB and SET protocols. RESULTS: According to repeated measures ANOVA, there were no significant postural sway velocity main effects by time of day for any of the balance conditions. We found significant postural sway main effects by foam, stance and eyes. We also noted significant ANOVA between participants' differences for athlete status, but not for sex. SIGNIFICANCE: These results inform practitioners about the importance of controlling time-of-day between baseline and post-injury testing, which may allow for more flexible, accurate and reliable diagnosis and return-to-activity decisions. Athletes displayed better static postural control, possibly warranting different normative values for diagnostic comparison.

Exposure to Cold Unmasks Potential Biomarkers of Fibromyalgia Syndrome Reflecting Insufficient Sympathetic Responses to Stress.

OBJECTIVES: Fibromyalgia syndrome (FMS) is a chronically painful condition whose symptoms are widely reported to be exacerbated by stress. We hypothesized that female patients with FMS differ from pain-free female controls in their sympathetic responses, a fact that may unmask important biomarkers and factors that contribute to the etiology of FMS. MATERIALS AND METHODS: In a pilot study, blood pressure (BP), skin temperature, thermogenic activity, circulating glucose, and pain sensitivity of 13 individuals with FMS and 11 controls at room temperature (24°C) were compared with that after exposure to cold (19°C). RESULTS: When measured at 24°C, BP, skin temperature, blood glucose, and brown adipose tissue (BAT) activity, measured using F-fluorodeoxyglucose positron-emission tomography/computed tomography, did not differ between controls and individuals with FMS. However, after cold exposure (19°C), BP and BAT activity increased in controls but not in individuals with FMS; skin temperature on the calf and arm decreased in controls more than in individiuals with FMS; and circulating glucose was lower in individiuals with FMS than in controls. Pain sensitivity did not change during the testing interval in response to cold. DISCUSSION: The convergence of the effect of cold on 4 relatively simple measures of thermogenic, cardiovascular, and metabolic activity, each regulated by sympathetic activity, strongly indicate that individuals with FMS have impaired sympathetic responses to stress that are observable and highly significant even when measured in extraordinarily small sample populations. If insufficient sympathetic responses to stress are linked to FMS, stress may unmask and maximize these potential clinical biomarkers of FMS and be related to its etiology.

Review of overlap between thermoregulation and pain modulation in fibromyalgia.

Fibromyalgia (FM) 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 FM given that cold initiates thermogenesis in brown adipose tissue through adrenergic activity, whereas warmth suspends thermogenesis. Although females have a higher incidence of FM and 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 FM 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 FM. In the periphery, sympathetic nerves to brown adipose also project to surrounding tissues, including tender points characterizing FM. As a result, the musculoskeletal hyperalgesia associated with conditions such as FM may result from referred pain in the adjacent muscle and skin.

Forced swim-induced musculoskeletal hyperalgesia is mediated by CRF2 receptors but not by TRPV1 receptors.

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.

Dietary quercetin supplementation is not ergogenic in untrained men.

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.

High day-to-day reliability in lower leg volume measured by water displacement.

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.

Lack of both sex differences and influence of resting blood pressure on muscle pain intensity.

OBJECTIVE: To test whether muscle pain intensity caused by different intensities of unaccustomed eccentric exercise was moderately and negatively associated with resting blood pressure, and whether women reported higher pain ratings compared with men in response to such exercise. DESIGN AND SUBJECTS: The repeated measures design involved random assignment of 42 young adults (21 women, 7 per condition) to complete elbow extension exercises with a weight that was 80%, 100%, or 120% of their maximal voluntary concentric strength. Total work was equated by manipulating the number of repetitions performed in the 80% (n = 45), 100% (n = 36), and 120% (n = 30) condition groups. SETTING: A clinical laboratory in a large university in the southeastern U.S. OUTCOME MEASURES: Pain intensity ratings averaged over 3 days and resting blood pressure measurements averaged over 6 days. RESULTS: For both sexes there was a dose-response relation between the relative intensity of the unaccustomed eccentric exercise and mean pain intensity ratings. Mean pain intensity was not significantly related to systolic or diastolic blood pressure. There was no significant sex difference in pain intensity, although men's ratings, in contrast to expectations, tended to be higher than the women's ratings. CONCLUSIONS: The negative findings, contrary to those predicted from previous experiments in which other types of noxious stimuli have been used, suggest that sex and blood pressure associations with pain intensity are stimulus dependent.

Perceived exertion responses to novel elbow flexor eccentric action in women and men.

PURPOSE: The primary aim was to describe perceived exertion responses to different intensities of eccentric exercise in women and men. METHODS: 42 adults (21 men and 21 women, 7 per condition) completed elbow extension exercises with a weight corresponding to 80%, 100%, or 120% of maximal voluntary concentric strength. Total work was equated by manipulating the number of repetitions in the 80% (N = 45), 100% (N = 36), and 120% (N = 30) conditions. RESULTS: A two-way ANOVA showed significant main effects for the intensity and sex factors. Perceived exertion ratings were strongly dependent on exercise intensity, and women reported lower RPEs than men. A separate three-way mixed model ANOVA that included a repetition factor showed that perceived exertion ratings increased similarly across the first 30 repetitions in all exercise conditions. Significant partial correlations were found between mean RPE during the eccentric exercise bout, and the mean intensity of delayed-onset muscle pain measured from 12- to 72-h postexercise after controlling for the relative exercise intensity (r12.3 = 0.28) or the maximum concentric strength of the elbow flexors (r12.3 = 0.33). CONCLUSIONS: 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.