Physical activity to prevent obesity in young children: BMI in the BMJ.
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Biomedical subjects
Tim Cable
Publications and source records attributed to Tim Cable.
Ascorbic acid supplementation does not attenuate post-exercise muscle soreness following muscle-damaging exercise but may delay the recovery process.
Exercise involving lengthening muscle actions, such as downhill running, results in delayed onset muscle soreness (DOMS), which may be attributable to reactive oxygen species (ROS). Although exercise causes oxidative stress, any link between ROS and DOMS remains speculative. There is emerging evidence to suggest that ROS play an important physiological role, assisting in the recovery process and protecting the cell from future damage; however, this has not been fully established. Despite this uncertainty as to the precise role of ROS, attempts to prevent post-exercise ROS production through antioxidant intervention are still common. The study investigated the effects of ascorbic acid supplementation on ROS production and DOMS following downhill running. Subjects were assigned to two groups. The ascorbic acid group (group AA) received 1 g ascorbic acid 2 h pre-, and for 14 d post-downhill running, whilst the placebo group (Pl group) received a placebo. Blood samples were drawn pre-supplement, pre- and post-exercise, and then 1, 2, 3, 4, 7 and 14 d post-exercise for analysis of ascorbate, malonaldehyde and total glutathione. DOMS was assessed using a visual analogue scale and pressure algometry. Muscle function was assessed using isokinetic dynamometry. Plasma ascorbate was elevated throughout in group AA compared with the Pl group. Downhill running resulted in DOMS in both groups. Muscle function was impaired post-exercise in both groups, although a delayed recovery was noted in group AA. Malonaldehyde increased 4 d post-exercise in the Pl group only. Ascorbic acid supplementation attenuates ROS production following downhill running, without affecting DOMS. Furthermore, ascorbic acid supplementation may inhibit the recovery of muscle function.
Adult↗
Eccentric exercise, isokinetic muscle torque and delayed onset muscle soreness: the role of reactive oxygen species.
There is growing evidence that reactive oxygen species (ROS) are involved in the muscular damage and soreness that is observed following strenuous or unaccustomed exercise. This study investigated the relationship between delayed onset muscle soreness (DOMS), muscle function and ROS following downhill running using electron spin resonance (ESR) spectroscopy and plasma malonaldehyde (MDA) concentrations. Eight physically active male subjects participated in two trials consisting of 30 min of running at approximately 65% VO(2max) on the flat (FLA) or a 15% downhill (DWN) gradient. Venous blood samples were drawn before, immediately after, and then 24, 48 and 72 h post exercise, and at the same time DOMS and muscle function were assessed. Blood was analysed for markers of ROS, total and differential white blood cell count, and creatine kinase. Muscle function was measured on an isokinetic dynamometer, whilst DOMS was assessed using a visual analogue scale. An increase in ROS, detected via ESR spectroscopy and MDA, was observed following DWN ( P<0.05) but not following FLA. Increased DOMS and loss of muscle function were observed following DWN ( P<0.05) but not following FLA ( P>0.05). DWN resulted in a transient leukocytosis ( P<0.05) occurring immediately post-exercise but returning to pre-exercise levels by 24 h. Although DWN resulted in an increase in ROS production, the increase occurred after the peak decline in muscle function and DOMS, suggesting that there may be a disassociation in the temporal relationship between ROS, loss of muscle function and DOMS.
Adult↗
Exercise thermoregulation and hyperprolactinaemia.
The anterior pituitary hormone prolactin (PRL), measured in the peripheral blood circulation, reflects alterations in central brain 5-hydroxytryptamine (serotonin) and dopaminergic activity and is used as a marker of 'central fatigue' during active heat exposure. Significant correlations have consistently been found between PRL and core temperature (T(CORE)) during prolonged exercise. There has been no investigation into the relationship between PRL and other key thermoregulatory variables during exercise, such as weighted mean skin (T(SK)) and mean body temperature (T(B)), heat storage (HS), thermal gradient (T(GRAD)), heart rate (HR) and skin blood flow (cutaneous vascular conductance, CVC). Therefore, the aim of this study was to ascertain if a significant relationship exists between PRL and these thermoregulatory variables during prolonged exercise. Nine active male subjects conducted three trials of approximately 60% VO(2peak) at 70-80 rpm for 45 min on a semi-recumbent cycle ergometer at three different ambient temperatures [6 degrees C (Cold), 18 degrees C (Neutral) and 30 degrees C (Hot)] to elicit varying levels of thermoregulatory stress during exercise. Significant differences existed in T(SK), T(B), HS, T(GRAD) and CVC across the environmental conditions (p < 0.001). Core temperature (T(CORE)), HR and PRL were significantly elevated only in Hot (p < 0.05). Moderate correlations were found for T(CORE), T(SK), T(B), HS, T(GRAD), HR and CVC with post-exercise PRL (rho = 0.358-0.749). The end-of-exercise <38.0 degrees C T(CORE) responses were not (rho = -0.129, p > 0.05) but the >38.0 degrees C T(CORE) responses were (rho = 0.845, p < 0.001) significantly related to their corresponding PRL responses. The significant relationships between PRL release and T(SK), T(B), HS, T(GRAD), HR and CVC have extended previous research on T(CORE) and PRL release and indicate an association between these thermoregulatory variables, as well as T(CORE), and serotonergic/dopaminergic activity during prolonged exercise.
Adult↗