Alison Purvis

Effects of sock type on foot skin temperature and thermal demand during exercise

Many fabrics and clothing ‘systems’ have been designed to enhance heat balance and provide greater thermal comfort for the wearer. However, studies on the effects of socks have largely been ignored in clothing research. It has been suggested that the thermal state of the extremities may alter core temperature and mental stress may be a major determinant of skin blood perfusion on the foot. However, no definite conclusions have been drawn. The aim of this study was to examine the effects of two different sock types on foot skin temperature and to investigate any impact on whole body thermoregulation and energy expenditure. Sixteen subjects carried out two sessions of treadmill running exercise, one session wearing a standard running sock and one session wearing an ergonomic asymmetric fitted sock. The overall mean heart rate, core (aural) temperature, foot skin temperature, weighted mean skin temperature and sweat rate during exercise were not statistically significant between the sock conditions (p > 0.05). There was a consistent trend in all participants for the ergonomic sock to induce a higher core temperature and higher skin temperatures compared to the standard sock. Overall mean ratings of perceived exertion and ratings of thermal perception were similar for both sock conditions. Participant questionnaires highlighted a general perception that the ergonomic socks had superior cushioning but that the standard socks were comfortable to wear. Despite there being no significant physiological or thermal differences between socks, the ergonomic sock was perceived to be cooler and was the preferred sock which suggests that subjective perceptions may be more important than objective measurements when selecting a sock for wear during prolonged exercise.

The prolactin responses to active and passive heating in man.

The aim of this study was to compare the prolactin and blood pressure responses at identical core temperatures during active and passive heat stresses, using prolactin as an indirect marker of central fatigue. Twelve male subjects cycled to exhaustion at 60% maximal oxygen uptake ( ) in a room maintained at 33°C (active). In a second trial they were passively heated (passive) in a water bath (41.56 ± 1.65°C) until core temperature was equal to the core temperature observed at exhaustion during the active trial. Blood samples were taken from an indwelling venous cannula for the determination of serum prolactin during active heating and at corresponding core temperatures during passive heating. Core temperature was not significantly different between the two methods of heating and averaged 38.81 ± 0.53 and 38.82 ± 0.70°C (data expressed as means ±s.d.) at exhaustion during active heating and at the end of passive heating, respectively (P > 0.05). Mean arterial blood pressure was significantly lower throughout passive heating (active, 73 ± 9 mmHg; passive, 62 ± 12 mmHg; P < 0.01). Despite the significantly reduced blood pressure responses during passive heating, during both forms of heating the prolactin response was the same (active, 14.9 ± 12.6 ng ml−1; passive, 13.3 ± 9.6 ng ml−1; n.s.). These results suggest that thermoregulatory, i.e. core temperature, and not cardiovascular afferents provide the key stimulus for the release of prolactin, an indirect marker of central fatigue, during exercise in the heat.

Assessment Strategies to Support Higher Level Learning in Blended Delivery

A level 6 module was developed in order to implement innovative assessment strategies and encourage higher level learning. The module tutor (one of this paper’s authors) was seconded from teaching duties (40%) to the University’s academic development unit to work on the module transformation. The rationale for the redesign of the assessment strategy was to enhance the student learning experience whilst taking an innovative approach to computer aided learning and assessment. Information technology enabled assessment strategies and ways of using computer based assessment in higher level learning were examined. The redesigned module has been delivered two years running, and the students’ experience of the module evaluated following the final taught session each year. This paper outlines the experiences of the learners and the tutor and considers the potential for future development of blended learning and assessment.

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 ∼60% VO2peak at 70–80 rpm for 45 min on a semi-recumbent cycle ergometer at three different ambient temperatures [6°C (Cold), 18°C (Neutral) and 30°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 (ρ = 0.358–0.749). The end-of-exercise <38.0°C T CORE responses were not (ρ = −0.129, p > 0.05) but the >38.0°C T CORE responses were (ρ = 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.

The effects of phase control materials on hand skin temperature within gloves of soccer goalkeepers

In soccer, goalkeepers routinely wear gloves that may restrict heat loss from the hands and cause thermal discomfort. In order to alleviate this problem phase control materials (PCMs) have been incorporated into gloves to reduce heat load inside the glove, thereby maintaining a comfortable temperature. The aim of this study was to assess the efficacy of these materials during a simulation of goalkeeping activities. Seven subjects carried out two sessions of goalkeeperspecific exercise on a non-motorized treadmill, one session with a PCM glove and one session with a normal foam material glove (NFM). All sites of skin temperature measurement, except mean whole-body skin temperature, showed uniformly that the PCM glove caused a greater increase in skin temperature of the hand compared to the NFM glove. These results suggest that this particular specification of PCM promotes heat gain rather than heat loss and is therefore inappropriate to enhance thermal comfort in this setting.

Reliability of Intestinal Temperature Using an Ingestible Telemetry Pill System During Exercise in a Hot Environment

Abstract Ruddock, AD, Tew, GA, and Purvis, AJ. Reliability of intestinal temperature using an ingestible telemetry pill system during exercise in a hot environment. J Strength Cond Res 28(3): 861–869, 2014—Ingestible telemetry pill systems are being increasingly used to assess the intestinal temperature during exercise in hot environments. The purpose of this investigation was to assess the interday reliability of intestinal temperature during an exercise-heat challenge. Intestinal temperature was recorded as 12 physically active men (25 ± 4 years, stature 181.7 ± 7.0 cm, body mass 81.1 ± 10.6 kg) performed two 60-minute bouts of recumbent cycling (50% of peak aerobic power [watts]) in an environmental chamber set at 35° C 50% relative humidity 3–10 days apart. A range of statistics were used to calculate the reliability, including a paired t-test, 95% limits of agreement (LOA), coefficient of variation (CV), standard error of measurement (SEM), Pearsons correlation coefficient (r), intraclass correlation coefficient (ICC), and Cohens d. Statistical significance was set at p ⩽ 0.05. The method indicated a good overall reliability (LOA = ±0.61° C, CV = 0.58%, SEM = 0.12° C, Cohens d = 0.12, r = 0.84, ICC = 0.84). Analysis revealed a statistically significant (p = 0.02) mean systematic bias of −0.07 ± 0.31° C, and the investigation of the Bland–Altman plot suggested the presence of heteroscedasticity. Further analysis revealed the minimum “likely” change in intestinal temperature to be 0.34° C. Although the method demonstrates a good reliability, researchers should be aware of heteroscedasticity. Changes in intestinal temperature >0.34° C as a result of exercise or an intervention in a hot environment are likely changes and less influenced by error associated with the method.

Kinematics and neuromuscular recruitment during vertical treadmill exercise

The vertical treadmill (VertiRun) is an unresearched, partial weight-bearing exercise mode for lower limb rehabilitation. The user undertakes a “running-like” action whilst body weight is supported by a bench and the limb is drawn downwards against overhanging resistance cables on a vertically hung nonmotorised treadmill. This study sought to describe the kinematics and neuromuscular recruitment during VertiRun exercise in the supine, 40°, and 70° postures. Twenty-one healthy male participants (age, 25±7 years; stature, 1.79±0.07 m; body mass, 77.7±8.8 kg) volunteered for sagittal plane kinematic analysis of the ankle, knee and hip and electromyography of lower limb musculature in all three postures. Results indicated similar kinematic and neuromuscular profiles in the 40° and 70° postures which differed from the supine. Regardless of posture, a basic movement pattern was observed where the hamstrings and gastrocnemius muscles were active to extend the hip, flex the knee, plantarflex the ankle and draw the leg down the treadmill belt in the contact phase. The rectus femoris and tibialis anterior were active to flex the hip and knee, and dorsiflex the ankle to draw the leg upwards during the swing phase. The vasti muscles were not active during VertiRun exercise. The VertiRun demonstrated similar kinematic and neuro-muscular patterns to overground gait, allows workload progression based on effort and posture changes, and is a low-impact exercise mode that could maintain physical fitness without loading injured tissues. This study suggests that the VertiRun could supplement rehabilitation programmes for lower-limb injuries.

Sprint interval training on the vertical treadmill improves aerobic and anaerobic running performance

The vertical treadmill (VertiRun) is an unresearched mode of exercise where users engage in a “running-like” action whilst body weight is supported by a recumbent bench and overhanging resistance cables are tethered to the user’s ankles. The purpose of this study was to determine the effects of training on a VertiRun and any cross-training effect on running performance. Thirty active males (age, 22±4 years; stature, 1.79±0.08 m; body mass, 78.5±12.6 kg) volunteered for this study. Participants’ aerobic and anaerobic running performance were determined by incremental maximum rate of oxygen consumption (VO2max) treadmill test and a maximum anaerobic running test (MART), respectively. Participants were matched and then randomly assigned to either a VertiRun group, 20-m shuttle sprint group or control group. The intervention consisted of 4–6, 30-sec all-out efforts with 4-min recovery between bouts, 3 days a week for 6 weeks. The pre- and postintervention VO2max and MART were analysed using a mixed repeated measures analysis of variance. MART increased by 4.5% in the VertiRun group (P=0.006) and 4% in the sprint group (P<0.001). VO2max increased by 6.2% in the VertiRun group (P=0.009) and 5.5% in the sprint group (P=0.020). The MART and VO2max of the control group were unchanged (P=0.910 and P=0.915, respectively). These data suggest that the VertiRun could be an effective cross-training mode for running and could supplement training programmes. Also, as VertiRun is a low-impact exercise it might be useful in the physical preparation of athletes returning to sport following lower limb injury.

Effect of hand cooling on body temperature, cardiovascular and perceptual responses during recumbent cycling in a hot environment

ABSTRACT The purpose of this study was to quantify physiological and perceptual responses to hand immersion in water during recumbent cycling in a hot environment. Seven physically active males (body mass 79.8 ± 6.3 kg; stature 182 ± 5 cm; age 23 ± 3 years) immersed their hands in 8, 14 and 34°C water whilst cycling at an intensity (W) equivalent to 50% O2peak for 60 min in an environmental chamber (35°C, 50% relative humidity). 8 and 14°C water attenuated an increase in body temperature, and lowered cardiorespiratory and skin blood flow demands. These effects were considered to be practically beneficial (standardised effect size > 0.20). There was a tendency for 8 and 14°C to extend exercise duration versus 34°C (>7%). Heart rate, intestinal, mean skin and mean body temperature were less in 8°C compared to 14°C; these differences were considered practically beneficial. Augmented heat loss at the palm-water surface might enable cooler blood to return to the body and limit physiological strain. These findings provide a mechanistic basis for continuous hand cooling and indicate that endurance exercise in hot environments could be improved using this method. Future research should investigate its effectiveness during cycling and running performance.