Dopamine is a neurotransmitter found in the retina. Delays in the visual evoked responses and abnormalities in contrast sensitivity occur in patients with Parkinson's disease. Improvement in the P100 has followed L-dopa therapy. Suspected abnormalities at the retinal level in Parkinson's disease are observed in reductions in photopic, scotopic, and pattern-derived electroretinograms. We studied 35 patients with Parkinson's disease and 26 controls of comparable age and visual acuities using visual evoked responses, color vision, and contrast sensitivity testing. Contrast sensitivity thresholds were significantly different at most frequencies tested, using both stationary and temporally modulated sinusoidal gratings. The total error score of the Farnsworth-Munsell 100 Hue Test revealed significant differences between the patients and controls. The contrast thresholds derived from certain spatial frequencies and the total error in color score were significantly related to the duration of disease. A stepwise discriminant analysis correctly identified 94% of the patients and 94% of the controls. The significant error in chromatic discrimination observed in Parkinson's disease patients may be due to altered intraretinal dopaminergic synaptic activity in these patients.

All athletes completed the exercise task even though the gradual increase in aural temperature observed for the HP and LP groups suggests a degree of thermal imbalance. However, this was much less than observed for TP athletes, who demonstrated a much greater imbalance in temperature regulation. Increasing the exercise or environmental strain may result in the thermoregulatory responses of athletes with a spinal cord injury being compromised.

The increased participation in wheelchair sports in conjunction with environmental challenges posed by the most recent Paralympic venues has stimulated interest into the study of thermoregulation of wheelchair users. This area is particularly pertinent for the spinal cord injured as there is a loss of vasomotor and sudomotor effectors below the level of spinal lesion. Studies within this area have examined a range of environmental conditions, exercise modes and subject populations. During exercise in cool conditions (15-25 degrees C), trained paraplegic individuals (thoracic or lumbar spinal lesions) appear to be at no greater risk of thermal injury than trained able-bodied individuals, although greater heat storage for a given metabolic rate is evident. In warm conditions (25-40 degrees C), trained subjects again demonstrate similar core temperature responses to the able-bodied for a given relative exercise load but elicit increased heat storage within the lower body and reduced whole-body sweat rates, increasing the risk of heat injury. The few studies examining a wide range of lesion levels have noted that, for paraplegic individuals where heat production is matched by available sweating capacity, excessive heat strain may be offset. Studies relating to tetraplegic subjects (cervical spinal lesions) are fewer in number but have consistently shown this population to elicit much faster rates of core and skin temperature increase and thermal imbalance in both cool and warm conditions than paraplegic individuals. These responses are due to the complete absence or severely reduced sweating capacity in tetraplegic subjects. During continuous exercise protocols, the main thermal stressor for tetraplegic subjects appears to be environmental heat gain, whereas during an intermittent-type exercise protocol it appears to be metabolic heat production. Fluid losses during exercise and heat retention during passive recovery from exercise are related to lesion level. Future research is recommended to focus on the specific role of absolute and relative metabolic rates, sweating responses, training status and more sport- and vocation-specific exercise protocols.

Resting energy expenditure of persons with a spinal cord injury (SCI) is generally lower than that seen in able-bodied (AB) individuals due to the reduced amounts of muscle mass and sympathetic nervous system available. However, outside of clinical studies, much less data is available regarding athletes with an SCI. In order to predict the energy expenditure of persons with SCI, the generation and validation of prediction equations in relation to specific levels of SCI and training status are required. Specific prediction equations for the SCI would enable a quick and accurate estimate of energy requirements. When compared with the equivalent AB individuals, sports energy expenditure is generally reduced in SCI with values representing 30-75% of AB values. The lowest energy expenditure values are observed for sports involving athletes with tetraplegia and where the sport is a static version of that undertaken by the AB, such as fencing. As with AB sports there is a lack of SCI data for true competition situations due to methodological constraints. However, where energy expenditure during field tests are predicted from laboratory-based protocols, wheelchair ergometry is likely to be the most appropriate exercise mode. The physiological and metabolic responses of persons with SCI are similar to those for AB athletes, but at lower absolute levels. However, the underlying mechanisms pertaining to substrate utilization appear to differ between the AB and SCI. Carbohydrate feeding has been shown to improve endurance performance in athletes with generally low levels of SCI, but no data have been reported for mid to high levels of SCI or for sport-specific tests of an intermittent nature. Further research within the areas reviewed may help to bridge the gap between what is known regarding AB athletes and athletes with SCI (and other disabilities) during exercise and also the gap between clinical practice and performance.

The results of this study suggest that ingestion of NaHCO(3) improves sprint performance during prolonged intermittent cycling.