Lactic acid accumulation in cardiac patients performing circuit weight training: implications for exercise prescription.

Objective: Because blood lactic acid (LA) levels may be important in prescribing exercise for cardiac patients, this study documented the LA response to four different circuit weight training (CWT) protocols and compared these responses to both maximal treadmill and LA threshold values.

Design: Intervention study following a crossover trial design.

Setting: A phase III community-based setting.

Circuit weight training in cardiac patients: determining optimal workloads for safety and energy expenditure.

Background: While most studies suggest circuit weight training (CWT) to be safe in cardiac rehabilitation populations, few investigators have controlled variables known to impact CWT intensity. Therefore, the purposes of this study were to determine the energy cost and evaluate safety of cardiac patients while varying rest interval duration and lifting load in a CWT format.

Methods: Nine male subjects with documented coronary artery disease had maximal oxygen uptake (VO2max), one-repetition maximum (1-RM), and body composition tested.

Physiologic responses of cardiac patients to supine, recumbent, and upright cycle ergometry.

Physiological responses were compared in nine stable male cardiac patients (mean +/- standard error (SE): age, 68.3 +/- 8.1 years; height, 172.

Postexercise oxygen consumption in trained females: effect of exercise duration.

Many research studies report the long-lasting elevation of metabolism following exercise. However, little is known regarding the impact of duration and intensity on this phenomenon, particularly in trained women in whom the time of the menstrual cycle has been controlled. This study examined the effects of a constant walking intensity (70% of maximal oxygen uptake (VO2max)) on the treadmill at various levels of duration (20, 40, and 60 min) on 3-h recovery of oxygen uptake (VO2).

Effects of frequency and duration of exercise sessions on physical activity levels and adherence.

The purpose of this study was to assess the relations among physical activity, adherence, and frequency and duration of exercise sessions for 33 male and female sedentary university students. Analysis indicated that frequency and duration of the exercise program did not significantly affect adherence. However, frequency and duration of the exercise sessions did significantly affect leisure activity once the structured exercise program terminated.

Reflex venomotor responses to lower body negative pressure following endurance training.

The effect of endurance training on reflex venomotor control during an orthostatic challenge was investigated in 11 sedentary male volunteers. An exercise (E) group (n = 6) underwent 12 weeks of endurance exercise training, whereas a control (C) group (n = 5) remained sedentary. Training significantly increased VO2max values in E (pre-training: 37.

Changes in plasma volume during bed rest: effects of menstrual cycle and estrogen administration.

Bed rest (BR) is associated with a decrease in plasma volume (PV), which may contribute to the impaired orthostatic and exercise tolerances seen immediately after BR. The purpose of this study was to determine whether increases in blood estrogen concentration, either during normal menstrual cycles or during exogenous estrogen administration, would attenuate this loss of PV. Nineteen healthy women (21-39 yr of age) completed the study.

Effect of exercise hemoconcentration and hyperosmolality on exercise responses.

We investigated the effects of a decrease in plasma volume (PV) and an increase in plasma osmolality during exercise on circulatory and thermoregulatory responses. Six subjects cycled at approximately 65% of their maximum O2 uptake in a warm environment (30 degrees C, 40% relative humidity). After 30 min of control (C) exercise (no infusion), PV decreased 13.

Cardiovascular response to lower body negative pressure (LBNP) following endurance training.

Eleven sedentary male volunteers were assigned to either an exercise (E) group (n = 6; endurance exercise for 12 weeks) or a control (C) group (n = 5; no exercise). After training, E significantly increased (p less than 0.01) their VO2max (pretraining: 37.

Effect of prolonged bed rest on lung volume in normal individuals.

Pulmonary function was assessed in supine subjects before, during, and after three separate bed-rest studies of 11 and 12 days duration. Forced vital capacity (FVC) increased during bed rest in each subject. Total lung capacity (TLC) was measured by helium dilution in one bed-rest study and increased in each subject, while residual volume and functional residual capacity of the respiratory system did not change.

Heat stress associated with the use of vapor-barrier garments.

Use of personal protective devices in the workplace, while intended to diminish risk of injury, may in some cases increase personal risk from environmental hazards. A case of a juvenile diabetic with complaints of near syncope while working in a plastics laminating process is analyzed. Although his symptoms might be attributed to a variety of causes, they were traced to the effects of heat stress related to wearing vapor-barrier disposable coveralls in a warm environment (85 degrees F).

Effect of positive-pressure breathing on cardiovascular and thermoregulatory responses to exercise.

Five healthy male volunteers performed 20 min of both seated and supine cycle-ergometer exercise (intensity, 50% maximal O2 uptake) in a warm environment (Tdb = 30 degrees C, relative humidity = 40-50%) with and without breathing 10 cmH2O of continuous positive airway pressure (CPAP). The final esophageal temperature (Tes) at the end of 20 min of seated exercise was significantly higher during CPAP (mean difference = 0.18 +/- 0.

Exercise, performance and temperature control: temperature regulation during exercise and implications for sports performance and training.

Thermoregulation is an important consideration not only for athletic performance but also for the safety of the athlete. This article presents a broad overview of the mechanisms by which body heat is dissipated in an individual exercising in a hot environment. Particularly emphasised are more recent views of body heat loss mechanisms and the influences of non-thermal inputs, such as effects due to changing blood volume or blood flow distribution.

Cardiac output and skin blood flow in lean and obese individuals during exercise in the heat.

Five obese (% body fat greater than or equal to 27%) and five relatively lean (% body fat less than 20%) men performed upright exercise on a cycle ergometer at intensities of 30, 50, and 70% of their maximal aerobic power [VO2max (ml X kg fat-free wt-1 X min-1)] in both a thermoneutral [dry bulb temperature (Tdb) = 22 degrees C, wet bulb temperature (Twb) = 14 degrees C] and a hot (Tdb = 38 degrees C, Twb = 20 degrees C) ambient environment. Cardiac output (Q) was measured by CO2 rebreathing and forearm blood flow (FBF) was measured by venous occlusion plethysmography. Esophageal temperature (Tes) was measured by a thermocouple placed in the esophagus at approximately heart level, and mean skin temperature (Tsk) was calculated from the average of thermocouple readings from six skin sites.