Developing a new device for continuously recording, in vivo, the excretion rate of sweat (perspiration) in humans.

BACKGROUND: Some methodologies used for evaluating sweat production and antiperspirants are of a stationary aspect, that is, most often performed under warm (38°C) but resting conditions in a rather short period of time. The aim is to develop an electronic sensor apt at continuously recording sweat excretion, in vivo, during physical exercises, exposure to differently heated environments, or any other stimuli that may provoke sweat excretion. MATERIAL AND METHODS: A sensor (20 cm2 ) is wrapped under a double-layered textile pad. Fixed onto the armpits, these two arrays of electrodes are connected to electronic system through an analog multiplexer. A microcontroller is used to permanently record changes in the conductance between two electrodes during exposure of subjects to different sweat-inducing conditions or to assess the efficacy of applied aluminum hydrochloride (ACH)-based roll-ons at two concentrations (5% and 15%). RESULTS: In vitro calibration, using a NaCl 0.5% solution, allows changes in mV to be related with progressively increased volumes. In vivo, results show that casual physical exercise leads to sweat excretions much higher than in warm environment (37 or 45°C). Only, an exposure to a 50°C environment induced comparable sweat excretion. In this condition, sweat excretions were found similar in both armpits and both genders. Decreased sweat excretions were recorded following applications of ACH, with a dose effect. CONCLUSION: Developing phases of this new approach indicate that usual method or guidelines used to determine sweat excretions in vivo do not reflect true energy expenditure processes. As a consequence, they probably over-estimate the efficacy of antiperspirant agents or formulae.

Acute and 2 days delayed effects of exhaustive stretch-shortening cycle exercise on barefoot walking and running patterns.

This study investigated the acute and 2 days delayed influences of exhaustive stretch-shortening cycle exercise (SSC) on barefoot walking and running gait patterns. The SSC exercise was performed on a sledge apparatus, on which the subjects (N = 10) repeated until exhaustion intermittent series of 25 bilateral submaximal rebounds. Maximal drop-jumps and submaximal barefoot treadmill walking and running were performed before (PRE) and after (POST) the exhaustive exercise and repeated 48 h (D2) later. Electromyographic activity and 3D kinematics of the right lower limb and foot were recorded for 15 s at gait initiation (BEG) and at the end (END: at 3 min of walk and 5 min of run). The exhaustive SSC exercise resulted in 6% reductions in maximal drop jump performance at POST and D2, and affected mostly both gait patterns at D2. The walking pattern presented compensatory neural adjustments within the triceps surae muscle group. This expected pain-induced protective strategy of the soleus muscle was sufficient to preserve the kinematics pattern. The running condition revealed a major knee strategy, which might support the concept of pain protective strategy of knee extensor muscles at the expense of impact cushioning. Regardless the testing session, most parameters showed fatigue-induced changes at gait initiation (BEG), which were opposite to subsequent BEG to END adjustments. This is likely to support anticipatory strategies rather than progressive adjustments during the exercise.

Characterisation of forces exerted by the entire hand during the power grip: effect of the handle diameter.

The objective of this study was to analyse the effect of the handle diameter on the grip forces exerted by the hand during a maximal power grip task. A handle ergometer, combining six instrumented beams and a pressure map, was used to determine the forces exerted by the palm side of the hand regrouping data from 10 anatomical sites (fingertips, phalanges, thumb, palm…). This methodology provided results giving new insight into the effect of the handle diameter on the forces exerted by the hand. First, it appeared that the relationship between the hand length/handle diameter ratio and the maximal grip force fit a U-inverted curve with maximal values observed for a handle diameter measuring 17.9% of the hand length. Second, it was showed that the handle diameter influenced the forces exerted on the anatomical sites of the hand. Finally, it was showed that the handle diameter influenced the finger force sharing particularly for the index and the little fingers. Practitioner Summary: This study analysed the effect of the handle diameter on the grip forces exerted by the hand during a maximal power grip force. This study showed that measurement of the totality of the forces exerted at the hand/handle interface is needed to better understand the ergonomics of handle tools. Our results could be re-used by designers and clinicians in order to develop handle tools which prevent hand pathologies.

The electrically assisted bicycle: an alternative way to promote physical activity.

OBJECTIVE: The aim of this study was to analyze the physiologic demand of pedaling on an electrically assisted bicycle to test its potential as an alternative method to perform exercise. DESIGN: Twenty participants (ten trained vs. ten untrained in endurance) novice in the electrically assisted bicycle performed the same cycling protocol composed of nine 5-min submaximal cycling periods without electrical support (NO), with a light support (S1), or with a high support (S4). The cycling conditions were tested at two different imposed speeds (16 and 21 km·hr(-1)) and one freely chosen speed (mean [SD], 18.1 [0.7] km·h(-1)). RESULTS: Mean power output, intensity, and energy expenditure were significantly lowered by the use of an electrical support, in similar proportions between the groups. For all subjects, the intensity of the electrically assisted bicycle in all measured conditions (S1 or S4) was sufficiently high to achieve the standards for moderate-intensity health-enhancing physical activity for adults (>3 metabolic equivalents). However, a vigorous intensity (>6 metabolic equivalents) was reached with the NO and S1 supports in the untrained group whatever the cycling speed and only at 21 km·hr(-1) with the light support (S1) in the endurance-trained group. CONCLUSIONS: By reducing the perceived sensation of effort while maintaining a sufficiently high energy expenditure, the electrically assisted bicycle has a great potential to promote physical activity in industrialized societies.