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Biomedical subjects

R J Lockwood

Publications and source records attributed to R J Lockwood.

3 recordsLinked to original sources
PubMed1994

Thermoregulation of paraplegic and able bodied men during prolonged exercise in hot and cool climates.

The purpose of this study was to compare the thermoregulatory responses of trained paraplegics (TP) and able bodied subjects (AB) performing submaximal exercise of the same relative intensity in both hot and cool conditions. Five TP (lesion range T12 to L3) and five AB subjects experienced in wheelchair use performed 60 minutes of constant load (55-60% of VO2 max) arm ergometry exercise in 37 degrees C and 15 degrees C climatic conditions. Heart rate (HR), sweat rate and rectal (Tr) and skin (Tsk) temperatures were recorded. In the hot climate the TP subjects recorded a significantly greater change in Tsk (delta Tsk) from 0 to 60 minutes of exercise than the AB subjects, because of greater thigh and calf temperatures, but no other significant differences were found between these groups. In the cool climate no significant differences were observed between the TP and AB groups. It was concluded that TP have a similar thermoregulatory ability to AB subjects who perform identical prolonged exercise in hot and cool conditions, although their lower limb skin temperatures are greater, probably because of venous pooling in the legs. While these results are a promising indication of the ability of TP to thermoregulate effectively while exercising in the, heat caution regarding their participation in endurance competitions in hot conditions should be expressed until data collected during wheelchair exercise (rather than arm ergometry) in the heat is available.

Adult↗
PubMed1993

The muscle silent period following transcranial magnetic cortical stimulation.

Transcranial magnetic stimulation (TMS) of the motor cortex during tonic muscle contraction produces a motor evoked potential followed by a silent period in the electromyogram. We sought to characterize the TMS induced silent period and to compare it to the silent period induced by supramaximal peripheral nerve stimulation. TMS was delivered to the motor cortex using a 9 cm diameter circular coil and the surface electromyogram was recorded from the contralateral abductor pollicis brevis muscle in six normal subjects. Increasing TMS stimulus intensity from 10 to 50% above threshold resulted in an increase in the duration of the silent period from a mean of 50 ms to 185 ms. Increasing the level of tonic muscle contraction from 5% of maximum to maximum resulted in a decrease in silent period duration from a mean of 155 ms to 133 ms. In contrast, the duration of the silent period following supramaximal median nerve stimulation showed greater shortening under similar conditions, from a mean of 160 ms at 5% of maximum contraction to 99 ms at 75% of maximum contraction. The TMS induced silent period was present during a TMS induced increase in the reaction time for a ballistic movement, the onset of movement being delayed until the end of the silent period. Peripheral nerve stimulation did not produce a delay in movement onset. The present findings favour a cortical origin for the TMS induced silent period, probably on the basis of intracortical inhibition, rather than peripheral inhibition of spinal motoneurones which is considered to be the basis for the silent period following peripheral nerve stimulation.

Adult↗