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J Brasher

Publications and source records attributed to J Brasher.

5 recordsLinked to original sources
PubMed1992

A height-adjusted step test for predicting maximal oxygen consumption in males.

A suitable testing device that is generally favored for estimating maximal oxygen consumption (VO2max) under field conditions or in environments where testing equipment is limited is the step test. Recently a mathematical model was reported to standardize the height of stepping for individuals of various heights. The purpose of this study was to validate this model in males. Thirty-three men aged 18 to 47 (x = 28) performed each of three rate-specific step tests and a Bruce treadmill test. Direct measurements of VO2max obtained from the treadmill test were correlated with a 15 second recovery heart rates after three different step tests were performed at stepping frequencies of 22, 26 and 30 ascents/minute. The correlation coefficients for prediction of VO2max from the recovery heart rate and directly measured oxygen consumption were 0.77 at 22 and 0.81 at 26 and 30 ascents/minute. Each relationship was statistically significant at the p < 0.01 level. It can be concluded that the single-stage height adjusted step test provides an effective predictor of VO2max in males and can be used when more complex methods of clinical testing are unavailable or not feasible.

Adolescent↗
PubMed1991

Physiological effects of wearing mouthguards.

Mouthguards are considered by most authorities to be an essential part of equipment for players participating in body-contact sports. Mouthguards provide excellent dental protection but not all players use them, complaining of breathing difficulties and problems with speaking. Although information exists concerning dental trauma and mouth protector use, there are no reported data that quantify the physiological effects of wearing mouthguards. The purpose of this study was to measure the ventilatory and gas exchange effects of wearing a mouthguard. Ten healthy men and seven women aged 20-36 years (mean(s.d.) 27.2(5.2) years) were used as subjects. Forced expiratory air volume at 1 s (FEV1) and peak expiratory flow rates (PEF) were measured on each subject while wearing either no mouthguard or one of three different over-the-counter mouthguards including one maxillary (mouthguard 1) and two different bimaxillary guards (mouthguards 2 and 3). To determine the effects of wearing each of the mouthguards during exercise, oxygen consumption (VO2) was measured while exercising on a cycle ergometer for 5 min at a light and heavy workload. An ANOVA of repeated measures was used to determine statistical differences. In each case, the wearing of a mouthguard significantly (P less than 0.05) reduced FEV1 and PEF in comparison with no mouthguard. FEV1 was reduced 8% with mouthguard 1, and 12% and 14% with mouthguards 2 and 3 respectively. PEF was reduced by 7, 15 and 15.8% with mouthguards 1, 2 and 3 respectively. The wearing of the different mouthguards did not significantly change VO2 while exercising at the lower work level whereas VO2 was significantly ( P < 0.05) reduced at the heavier workload. This surprising reduction in VO2 during heavy exercise may be due to a 'pursed-lip' type of breathing which has been shown to decrease CO2 tension, increase oxygenation and exercise tolerance. It can be concluded that although mouthguards may be perceptably uncomfortable and restrict forced expiratory air flow, they appear to be beneficial in prolonging exercise by improving ventilation and economy.

Adult↗
PubMed1991

Heat illness in football players in Alabama.

Fall football practice in Alabama generally begins during the later months of summer during some of the hottest periods of the year. Exercise during these periods significantly exposes young athletes to risks of heat illness and possible death and is made even more dangerous while training in full football uniform. In order to delineate specific guidelines to reduce the risk of heat illness, optimal practice times and fluid replacement schedules were studied for the state of Alabama. A review of five-year climatological data (1984-1988) for the months of August and September were conducted for four geographic regions of the state. A study of the data revealed that there were no environmental combinations at any time periods during the month of August for any locale in the state that would be considered safe for outdoors practice in full uniform. Similar results were recorded for September for cities in the south-central portion of the state. There were only two time periods during which players could practice outdoor with extreme caution. The periods were at 0900 and 1800 hrs in the north-central and northern portions of the state. If practice is conducted outdoors in Alabama during August and September, copious amounts of water should be consumed prior to practice; frequent water breaks should be scheduled throughout practice at which time each player should consume 150 - 200 ml; and the player should be carefully monitored for signs of heat illness.

Football↗