Biomedical subjects

A F Meintjes

Publications and source records attributed to A F Meintjes.

3 recordsLinked to original sources

PubMed1989

Improved physical fitness failed to alter the EEG patterns of sleep in young women.

We investigated the effect of a 12-week physical training programme on the sleep of nine unfit women. Data were collected at 0, 4, 8 and 12 weeks of the training programme. Changes in fitness were assessed by changes in maximal oxygen consumption (VO2max) and onset of blood lactate turn point (LTP). Lean body mass (LBM) was calculated from total body potassium measurements. The all-night sleep recordings were made following days during which the subjects carried out their normal daily routines and did no extra exercise. Although cardiorespiratory fitness improved significantly as indicated by an increase in both VO2max and LTP, there was no change in LBM. The improvement in cardiorespiratory fitness did not result in any changes in the sleep parameters measured. Other workers have reported an improvement in sleep quality in eight army recruits during their basic training. The male recruits showed improved cardiorespiratory fitness and an increase in muscle bulk. These results suggest that increased fitness only facilitates sleep when there is an associated increase in LBM. Alternatively it may be that the response of sleep to improved fitness is sex-linked.

Adult↗

PubMed1988

Daily exposure to forty percent oxygen causes a decrease in platelet count.

A study was undertaken to evaluate a previous observation made in this laboratory that hyperoxic treadmill training is associated with a decrease in the circulating platelet count (PLT). The subjects studied breathed air containing 40% oxygen for 30 min/day, 5 days/week, for 6 weeks, while at rest in the seated position. Such exposure resulted in a consistent fall in PLT between day 1 and day 5 of each week (P less than .01). In addition, there was a progressive decline in PLT over the 6 weeks of exposure to the hyperoxic air, PLT being inversely correlated with the duration of hyperoxic exposure (rs = -0.886, P less than .02). The total decrease in PLT over the 6 weeks was 56 +/- 46 x 10(9) l(-1) (P less than .025). Not surprisingly, these changes were mirrored in the plateletcrit (Pct). The decrease in PLT did not appear to be secondary to either hemodilution or reduced erythropoietic stimulation. The mechanism of production and the biological significance of these changes remain to be elucidated.

Administration, Inhalation↗

PubMed1988

Submaximal exercise effects on sleep patterns in young women before and after an aerobic training programme.

We studied the sleep patterns of nine young women when sedentary (untrained) and following a 12 week physical fitness training programme. A comparison of baseline sleep patterns and of sleep patterns following one hour of submaximal exercise performed in the evening was carried out at 0 and 12 weeks. The submaximal exercise task was for each subject to cycle for one hour at 70% of her maximal oxygen consumption (VO2 max) as measured when untrained and on completion of the training programme respectively. Changes in fitness were assessed by changes in VO2 max and anaerobic threshold (AT). On the day leading to the all night baseline sleep recordings the subjects carried out their normal daily routines and did no specific exercise. Lean body mass (LBM) was calculated from total body potassium measurements before and after training. A significant improvement in cardiorespiratory fitness did not result in any changes in baseline sleep parameters. The response to the submaximal exercise was an increase in stage 2 NREM sleep and a decrease in slow-wave sleep (SWS, stages 3 & 4) which is possibly indicative of a stress effect. However, in the trained compared to the untrained state, SWS was significantly higher after an exercise load.

Adult↗