European journal of applied physiology
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Eur. J. Appl. Physiol. · Aug 2012
Reduction in corticospinal inhibition in the trained and untrained limb following unilateral leg strength training.
This study used transcranial magnetic stimulation to measure the corticospinal responses following 8 weeks of unilateral leg strength training. Eighteen healthy, non-strength trained participants (14 male, 4 female; 18-35 years of age) were matched for age, gender, and pre-training strength; and assigned to a training or control group. The trained group participated in unilateral horizontal leg press strength training, progressively overloaded and wave periodised, thrice per week for 8 weeks. ⋯ The trained leg showed an increase in strength of 21.2% (P = 0.001) and 29.0% (P = 0.007, compared to pre-testing) whilst the untrained contralateral leg showed 17.4% (P = 0.01) and 20.4% (P = 0.004, compared to pre-testing) increases in strength at 4 and 8 weeks, respectively. EMG and corticospinal excitability did not change; however, corticospinal inhibition was significantly reduced by 17.7 ms (P = 0.003) and 17.3 ms (P = 0.001) at 4 and 8 weeks, respectively, in the trained leg, and 25.1 ms (P = 0.001) and 20.8 ms (P = 0.001) at 4 and 8 weeks, respectively, in the contralateral untrained leg. This data support the theory of corticospinal adaptations underpinning cross-education gains in the lower limbs following unilateral strength training.
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Eur. J. Appl. Physiol. · Jul 2012
Experimental knee pain impairs postural stability during quiet stance but not after perturbations.
The objective of this study was to examine the effect of experimental knee-related pain on postural control. Twelve healthy subjects stood as quietly as possible on a movable force platform (that measured the centre of pressure and provided fast perturbations) before, during, and after experimental knee-related pain. Lower limb electromyographic (EMG) activity and joint angles were measured. ⋯ The additional impairment by bilateral pain suggests that the non-painful limb in unilateral pain conditions compensates for the impaired postural control. These results show that knee-related pain impairs postural stability during quiet standing, indicating the vulnerability of patients with knee pain to falls. This measure could potentially help clinicians who seek to assess how pain responses may contribute to patient's postural control and stability during quiet standing.
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Eur. J. Appl. Physiol. · Jun 2012
Development of a perceptual hyperthermia index to evaluate heat strain during treadmill exercise.
Fire suppression and rescue is a physiologically demanding occupation due to extreme external heat as well as the physical and thermal burden of the protective garments. These conditions challenge body temperature homeostasis and results in heat stress. Accurate field assessment of core temperature is complex and unreliable. ⋯ Thermal sensation increased from baseline (1.78 ± 0.77) to termination (4.50 ± 0.68). Perceived exertion and thermal sensation were measured concurrently with body core temperature to develop a two-dimensional graphical representation of three exertional heat strain zones representative of a range of mean body core temperature responses such that low risk (green) incorporated 36.0-37.4°C, moderate risk (yellow) incorporated 37.5-37.9°C, and high risk (red) incorporated 38.0 to greater than 40.5°C. The perceptual hyperthermia index (PHI) may provide a quick and easy momentary assessment of the level of risk for exertional heat stress for firefighters engaged in fire suppression that may be beneficial in high-risk environments that threaten the lives of firefighters.
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Eur. J. Appl. Physiol. · Jun 2012
Reliability of near infrared spectroscopy (NIRS) for measuring forearm oxygenation during incremental handgrip exercise.
The purpose of this study was to test the reliability of a new handgrip exercise protocol measuring forearm oxygenation in 20 healthy subjects on two occasions. The retest took place 48 h later and at the same time of the day. The incremental exercise consisted of 2 min steps of cyclic handgrip contraction (1/2 Hz) separated by 1 min of recovery. ⋯ The absolute SmO(2) values showed reliable ICC's for every submaximal intensity except at 60% MVC. An ICC of r = 0.774 (p < 0.001) was found at maximal intensity. The results of the present study show that deoxy[Hb + Mb] and SmO(2) responses during this protocol are highly reliable and indicate that this protocol could be used to get insight into deoxygenation and oxygen saturation in a population with low exercise tolerance.
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Eur. J. Appl. Physiol. · May 2012
Cognitive function following treadmill exercise in thermal protective clothing.
Occupational injuries are common among firefighters who perform strenuous physical exertion in extreme heat. The thermal protective clothing (TPC) worn by firefighters inhibits normal thermoregulation, placing the firefighter at risk of hypohydration and hyperthermia that may result in cognitive decline. We tested whether cognitive function changes after treadmill exercise in TPC. ⋯ Recall on a memory test was reduced 60 and 120 min after exercise. The mean of the 10 slowest reaction times increased in the 120 min after exercise. Fifty minutes of treadmill exercise in TPC resulted in near maximal physiologic strain but alterations in neurocognitive performance were not noted until an hour or more following exercise in TPC.