Average Work Rate Research Articles

O2 Uptake in hyperthyroidism during constant work rate and incremental exercise

To investigate the effect of hyperthyroidism on the pattern and time course of O2 uptake (VO2) following the transition from rest to exercise, six patients and six healthy subjects performed cycle exercise at an average work rate (WR) of 18 and 20 W respectively. Cardiorespiratory variables were measured breath-by-breath. The patients also performed a progressively increasing WR test (1-min increments) to the limit of tolerance. Two patients repeated the studies when euthyroid. Resting and exercise steady-state (SS) VO2 (ml.kg-1.min-1) were higher in the patients than control (5.8, SD 0.9 vs 4.0, SD 0.3 and 12.1, SD 1.5 vs 10.2, SD 1.0 respectively). The increase in VO2 during the first 20 s exercise (phase I) was lower in the patients (mean 89 ml.min-1, SD 30) compared to the control (265 ml.min-1, SD 90), while the difference in half time of the subsequent (phase II) increase to the SS VO2 (patient 26 s, SD 8; controls 17 s, SD 8) were not significant (P = 0.06). The O2 cost per WR increment (delta VO2/delta WR) in ml.min-1.w-1, measured during the incremental period (mean 10.9; range 8.3-12.2), was always within two standard deviations of the normal value (10.3, SD 1). In the two patients who repeated the tests, both the increment of VO2 from rest to SS during constant WR exercise and the delta VO2/delta WRs during the progressive exercise were higher in the hyperthyroid state than during the euthyroid state.(ABSTRACT TRUNCATED AT 250 WORDS)

Energy and thermal regulation during bed rest and spaceflight.

In planning for long-duration (1- to 2-yr) space missions (microgravity), the availability of oxygen, water, and food is critical for survival. If astronauts would consume approximately 3,100 kcal and 2.2 liters of fluid per day, the requirements for a 2-yr flight would be 2,263,000 kcal and 1,606 liters for each astronaut. These estimates, based on limited microgravity simulation and flight data, include 1 h/day of moderate isotonic exercise. Each 30-min/day reduction in exercise training time would save 110,869 kcal and 91 liters of water per year. One daily 5-h extravehicular sortie at an average work rate of 1.7 l/min would require an additional 529,250 kcal and 1,095 liters of water per year. Results from microgravity simulation (bed rest) experiments suggest that 1) there is uncertainty whether basal metabolism is unchanged, 2) submaximal ergometer exercise oxygen uptake appears to be unchanged or lower, and 3) without vigorous exercise training near peak levels, the peak oxygen uptake is definitely reduced. In addition, the equilibrium level of exercise core temperature is elevated excessively by approximately 0.5 degrees C after bed-rest acclimation. Changes in the efficiency of work or metabolism in any or all of these conditions could affect nutritional requirements for long spaceflights. Further research is necessary to elucidate the metabolic factors that would be changed and the energy cost of intra- and extravehicular activity during prolonged exposure to microgravity.

The influence of training on endurance and blood lactate concentration during submaximal exercise.

The purpose of this study was to examine the effect of short-term training on maximum oxygen uptake (VO2 max) and two different measures of endurance performance. Endurance was determined for 15 female subjects (7 training, 8 control) as (1) exercise time to exhaustion at 80% VO2 max (T80%) and (2) the highest relative exercise intensity tolerable during a 30-minute test (T30 min), before and after a 6-week training period. In addition, VO2 max and the work rate equivalent to a blood lactate concentration of 4 mmol.l-1 (OBLA) were determined. Maximum oxygen uptake increased by 24% (p less than 0.01) for the training group (TG) and 7% (p less than 0.01) for the control group (CG). Cumulative average work rate (CAWR) during T30 min increased by 25% for the TG while there was no change for the CG. No significant difference was found pre- and post-training in the %VO2 max (estimated from CAWR) at which the TG and CG performed T30 min. Exercise time to exhaustion on T80% increased by 347% (p less than 0.01) and 16% (NS) for the TG and the CG respectively. Good correlations were found between VO2 max and CAWR (W) (pre-training r = 0.84; post-training r = 0.83), OBLA (W) and CAWR (W) (pre-training r = 0.89; post-training r = 0.88) and change in endurance time and the change in submaximal blood lactate concentration (r = 0.70, p less than 0.01). The results of this study suggest that the ability to sustain a high relative exercise intensity is not enhanced following short-term training.

Field performance evaluation of a manual rice transplanter

Field studies were conducted at the International Rice Research Institute, IRRI, farm on a manual rice transplanter, developed at the IRRI, under the following conditions: three levels of land preparation (low, medium and high); three water depths: 0–30 mm, 30–60 mm and 60–100 mm; and three seedling ages of 14–17, 18–21 and 22–25 days. The studies were extended to two other types of soils in farmers' fields to assess the results for the combination of land preparation, water depth and seedling age found to give minimum defective hills among treatment groups at the IRRI farm. At this farm the transplanter performed well, with less than 5% defective hills when using seedlings 14–17 days old in up to 100 mm water depth at the medium level of land preparation, up to 60 mm water depth at the low level of land preparation and up to 30 mm water in overprepared (high level) land. The transplanter also worked satisfactorily using 18–21 day old seedlings at up to 60 mm water depth in medium level prepared fields and up to 30 mm water in low level tilled fields. In sticky soils, at Zaragoza, the planting depth was greater and there were more defective hills of all kinds than at the IRRI farm. In the loam soils of Florida-Blanca the planting depth was less, and only floating hills were significantly more than at the IRRI farm. The machine had an average work rate of 0·034 ha/h.

Power requirements and mechanical efficiency of treadmill walking

The instantaneous energy levels of body segments are computed from kinematic measurements on a level treadmill at various speeds with freely chosen step rates and a constant speed with different imposed step rates. The changes in the energy levels of segments are combined to compute the average work rate required to accelerate the total body (positive internal work). This work is compared to total metabolic power consumption to obtain a minimal estimate of mechanical efficiency. The efficiency increases rapidly from 9% to 0.84 m/sec to a maximum of 23% at 1.70 m/sec. Thereafter, the efficiency slowly decreases with speed to 18% at 2.35 m/sec. When different step rates are imposed at one constant speed, the average positive work rate remains constant. This work rate level is identical to that required for walking at the same speed with self-determined (free) step rate. Thus, maximum gross efficiency results at the free step rate.

A Study and Discussion of the Average Work Rate of Psychiatric Patients being Trained by Industrial Therapy in Victoria

A Study and Discussion of the Average Work Rate of Psychiatric Patients being Trained by Industrial Therapy in Victoria