Endurance exercise : effects of high ambient temperature and central acting agents

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The effect of passive heating and face cooling on perceived exertion during exercise in the heat

Increased body temperature is thought to be an important component of the higher perception of exertion that is a feature of fatigue during exercise in the heat but a causal relationship has yet to be demonstrated. We have investigated the effect of passive heating on the perception of exertion during a standard bout of exercise and also assessed the effect of cooling the head on compensating for the increased body temperature on the feelings of exertion. Ten male subjects performed a 14-min cycling exercise [average power approximately 63% of maximum power output ( W(max))] at an ambient temperature of 35 degrees C at resting rectal temperature [mean (SD): 37.49 (0.27) degrees C; control (CON) trial] on one occasion, and after sitting in a sauna to raise rectal temperature [mean (SD): 38.95(0.13) degrees C; sauna (SAU) trial]. During the exercise, subjects reported their ratings of overall perceived exertion (RPE), perceived exertion of the legs (RPE(legs)) and thermal comfort (TC). A blood sample was collected by the end of the exercise for determination of plasma glucose, lactate and prolactin and haematocrit. RPE values were significantly elevated after passive heating [mean (SE): 14.5 (0.7) units in CON and 17.2 (0.5) units in SAU, at the end of exercise; P<0.001] as were the RPE(legs) ( P<0.01), while ratings of TC were similar in CON and SAU trials. Passive heating increased blood glucose ( P<0.05) but had no effect on lactate at the end of the exercise. Plasma prolactin was markedly elevated as a result of the sauna exposure [mean (SE): 1598 (152) versus 225 (31) mU l(-1) in SAU and CON trials, respectively; P<0.001]. Six of the subjects repeated the two trials but with the face cooled during exercise (trials CON(FAN) and SAU(FAN)) that was achieved by combining face fanning and spraying the face with a mist of cooled water. Face cooling decreased RPE values after sauna to a point that no differences between the two conditions existed. RPE(legs) scores and heart rate, however, remained higher in SAU(FAN) compared with CON(FAN) ( P<0.05). We conclude that hyperthermia is a causative element of the increased perception of exertion during submaximal exercise in the heat and that the effect of increased core temperature on the feelings of exertion is modulated by face cooling

The cadence and water temperature effect on physiological responses during water cycling

The aim of the study was to compare the maximal physiological responses during three protocols: maximal test on land cycle ergometer, maximal test on water cycling in an indoor pool at 27 8C (WC27) and at 31 8C (WC31). Moreover, the submaximal physiological responses were compared according cycling cadences and water temperatures during the water protocols. Ten young men were included and performed the protocols in separate days. Blood lactate (BL) concentration, heart rate (HR), oxygen uptake (V O2), ventilation (VE) and thermal comfort (TC) were collected during the exercise.The maximal HR and V O2 showed no significant differences between the protocols: HRmax: 189±7 (Land), 188±14 (WC27), 185±9 bpm (WC31) and _V O2max: 4.2±0.4 (Land), 4.1±0.5 (WC27) and 4.3±0.5 l min_1 (WC31). However, the maximal BL demonstrated significant lower values during the water protocols compared to the land protocol (p=0.018). All the submaximal physiological responses showed significant differences between the cadences (60, 70, 80 and 90 rpm). The effect of water temperature was significant for TC response (p_0.001) showing higher values at 31 8C than 27 8C (TCW27: 7±1 and TCW31:9±1). In conclusion, higher physiological responses were showed by increasing the cadence by 10 rpm and the subjects were more comfortable when cycling in the lower water temperature

Dynamic feet distance: a new functional assessment during treadmill locomotion in normal and thoracic spinal cord injured rats

Of all the detrimental effects of spinal cord injury (SCI), one of the most devastating is the disruption of the ability to perform functional movement. Very little is known on the recovery of hindlimb joint kinematics after clinically-relevant contusive thoracic lesion in experimental animal models. A new functional assessment instrument, the dynamic feet distance (DFD) was used to describe the distance between the two feet throughout the gait cycle in normal and affected rodents. The purpose of this investigation was the evaluation and characterization of the DFD during treadmill locomotion in normal and T9 contusion injured rats, using three-dimensional (3D) instrumented gait analysis. Despite that normal and injured rats showed a similar pattern in the fifth metatarsal head joints distance excursion, we found a significantly wider distance between the feet during the entire gait cycle following spinal injury. This is the first study to quantify the distance between the two feet, throughout the gait cycle, and the biomechanical adjustments made between limbs in laboratory rodents after nervous system injury.This research was supported by the Project UID/CVT/00772/2013 from FCT.info:eu-repo/semantics/publishedVersio

Promoting Nerve Regeneration in a Neurotmesis Rat Model Using Poly(DL-lactide--caprolactone) Membranes and Mesenchymal Stem Cells from the Wharton’s Jelly: In Vitro and In Vivo Analysis

In peripheral nerves MSCs can modulate Wallerian degeneration and the overall regenerative response by acting through paracrine mechanisms directly on regenerating axons or upon the nerve-supporting Schwann cells. In the present study, the effect of human MSCs from Wharton’s jelly (HMSCs), differentiated into neuroglial-like cells associated to poly (DL-lactide-ε-caprolactone) membrane, on nerve regeneration, was evaluated in the neurotmesis injury rat sciatic nerve model. Results in vitro showed successful differentiation of HMSCs into neuroglial-like cells, characterized by expression of specific neuroglial markers confirmed by immunocytochemistry and by RT-PCR and qPCR targeting specific genes expressed. In vivo testing evaluated during the healing period of 20 weeks, showed no evident positive effect of HMSCs or neuroglial-like cell enrichment at the sciatic nerve repair site on most of the functional and nerve morphometric predictors of nerve regeneration although the nociception function was almost normal. EPT on the other hand, recovered significantly better after HMSCs enriched membrane employment, to values of residual functional impairment compared to other treated groups. When the neurotmesis injury can be surgically reconstructed with an end-to-end suture or by grafting, the addition of a PLC membrane associated with HMSCs seems to bring significant advantage, especially concerning the motor function recovery