Myocardial infarction size and scar dimensions: the influence of activity.

OBJECTIVE: The purpose of this study was to determine myocardial infarct size and scar dimensions in experimentally infarcted rats that were randomly assigned to a moderate, mild, or no exercise condition after infarction. DESIGN: Pretest-posttest control group design (experimental). SUBJECTS: 57 male Harlan Sprague Dawley rats between 62 to 64 days of age and weighing 220 to 290 gm at the onset of the study. OUTCOME MEASURES: Infarction size, scar thickness, thinnest portion of scar. INTERVENTION: Mild exercise versus moderate exercise versus no exercise. RESULTS: No differences were found in infarct size, scar thickness, or thinnest portion of scar among the three groups. CONCLUSION: This study establishes that treadmill exercise, begun after an appropriate period of recovery, does not necessarily increase infarct size or scar thinning in the rat model. Further, animal and human studies are needed to fully explore the benefits and hazards of cardiac rehabilitation or exercise testing before or soon after discharge.

Weight-training effects on bone mineral density in early postmenopausal women.

We tested the hypothesis that weight training would be an effective modality in maintaining or increasing bone mineral density (BMD) at the lumbar spine, femoral neck, and bone mineral content (BMC) at the distal wrist in early postmenopausal women. A total of 17 women completed a 9 month weight-training program, and 9 women served as a control group. Resistance training occurred three times per week using exercises designed to increase muscular strength. Mean change in lumbar BMD in the weight-trained group (1.6 +/- 1.2%, mean +/- SEM) was significantly different from the change in the control group (-3.6 +/- 1.5%, p less than 0.01) over the 9 month period. No significant weight-training effect was detected at the femoral neck or distal wrist site. We conclude that weight training may be a useful exercise modality for maintaining lumbar BMD in early postmenopausal women.

Dietary carbohydrate and intensity of interval swim training.

We tested the effects of 9 d of a high-carbohydrate diet (80% of calories as CHO, 80% CHO diet) vs. a moderate-CHO diet (43% of calories as CHO, 43% CHO diet) on the abilities of collegiate swimmers to maintain a high intensity of interval swim training. Interval swim times and other physiological indices were recorded the last 5 d of each diet. Swim-interval distances ranged from 50-m interval sets to continuous 3000-m swims. There were no diet effects on mean swim velocities for any interval distance, and mean (+/- SEM) velocities for all swims were identical for both diets. There were no diet effects on the physiological indices; however, postswim blood lactate concentrations were higher after the 80% CHO diet. When mean +/- SEM daily caloric intake is 19.56 +/- 2.16 MJ (4675 +/- 516 kcal) for swimmers undertaking swim training to develop aerobic capacity, an 80% CHO diet provides no advantage over a 43% CHO diet for maintaining interval-swim-training intensity.

Menstrual irregularities in athletic women may be predictable based on pre-training menses.

With the use of a personally conducted survey the age at menarche, incidence of menstrual irregularity, whether training occurred before or after menarche, certain personality traits (anxiety, curiosity, anger), and the type of athletic activity performed, were assessed in 161 highly competitive women athletes of various types (e.g. professional dancers, basketball players, fencers, gymnasts, field hockey players, swimmers) and 65 age-matched nonathletic women. No significant difference was found between the mean age at menarche of competitive athletes 13.2 +/- 1.4 (SD) yrs and nonathletes 12.6 +/- 1.1 yrs or between athletes who trained before menarche 13.7 +/- 1.5 (SD) yrs compared to athletes who trained after menarche 12.7 +/- 1.3 yrs. However, there were significant differences in reference to the mean age at menarche for athletes and nonathletes when compared to current menstrual frequency (p less than 0.05) and for groups of athletes currently regular 12.9 +/- 1.2 (SD) yrs when compared to those currently irregular 13.4 +/- 1.6 yrs (PR greater than F = 0.0419), regardless of athletic status. Trait personality characteristics (anxiety, curiosity, anger) based on the Spielberger State-Trait Personality Inventory (STPI), showed no significance among the various athletes, or athletes compared to non-athletes, however, athletes having the highest mean anxiety scores 19.5 +/- 4.2 (SD) and lowest mean anger scores 17.0 +/- 3.6 (SD) had irregular menses. Predictability for the development of irregular menses was done by regression and stepwise discrimination with maximum improvement technique statistics using pre-training frequency of menses and post-training frequency of menses.(ABSTRACT TRUNCATED AT 250 WORDS)

Carbon dioxide storage capacity of endurance and sprint-trained athletes in exercise.

The purpose of this study was to compare CO2 storage capacity of endurance and sprint-trained athletes during steady state exercise. Ten subjects, five sprinters and five distance runners, performed a submaximal treadmill exercise at two different work rates, 45% and 65% of VO2max. CO2 storage capacity was determined by measuring the excess CO2 washout associated with hyperventilation, normalized for body weight and expressed per unit change in mixed venous PCO2 (ml kg-1 Torr-1). Mixed venous PCO2 (PvCO2) was measured by rebreathing equilibration. It was found that CO2 storage capacities of the runners were significantly (P less than 0.05) greater than the sprinters at the two work rates. The sprinters CO2 storage capacities were 2.69 and 2.14 ml kg-1 Torr-1 at low and high work rates, respectively. The corresponding mean values for the runners were 4.56 and 3.92 ml kg-1 Torr-1, respectively. These results may be explained by the metabolic differences between the sprinters and runners. The sprinters' musculature depends more heavily on the glycolytic metabolic pathway, which is associated with an increased lactate production and hence a reduction in the combining power of the blood for CO2 during exercise. At the low work rate, the body's storage capacity for CO2 was significantly (P less than 0.05) greater than the higher work rate for both groups. Obviously, at the higher work level more blood would be presented to the lungs per unit time allowing an increase in CO2 clearance from the body stores.

Physiological adjustments to higher- or lower-intensity exercise in elders.

A program of physical activity for people over 60 yr of age was developed to determine whether exercising at lower intensities (LI) is a significant conditioning stimulus. In addition, differences in aerobic capacities (VO2max) elicited by training at LI, as opposed to training at higher intensities (HI), were evaluated. Thirty-two volunteers over 60 yr of age (mean = 67.8 yr) participated in a 9-wk exercise program. After initial testing of VO2max on a cycle ergometer, subjects were assigned randomly to the HI, LI, or control group. Endurance training of the two exercise groups on cycle ergometers was maintained at 30-45% (N = 14) or 60-75% (N = 14) of the range (HRR) between the subject's resting and maximum heart rate for 25 min during each exercise session. These training intensities represented 57 and 70% of the VO2max of the LI and HI groups, respectively. Participants averaged three exercise sessions per week. Non-exercising volunteers served as control subjects. A one-way ANOVA with repeated measures was utilized for comparisons of retest, groups, and interaction. As a result of the exercise program, significant changes (P less than 0.005) in absolute (VO2max, 1 X min-1) and relative (VO2max, ml X min-1 X kg-1) aerobic capacities were realized within each training group while initial and post-training VO2max were not significantly different between the two groups. Similar changes were documented by a reduction in heart rate at submaximal exercise intensities and during recovery. It was concluded that exercising at LI (30-45% HRR) is an adequate training stimulus in older individuals and produces changes in VO2max that are comparable to those elicited by HI (60-75% HRR) training.

Gastric-emptying characteristics of two glucose polymer-electrolyte solutions.

Inadequate carbohydrate and fluids can limit physical performance; optimal delivery of both should be the goal of any beverage designed especially for the athlete. In this study, the gastric-emptying characteristics of two carbohydrate-electrolyte solutions were compared with water. The 5% carbohydrate solution contained 3% Polycose glucose polymers and 2% fructose, whereas the 7% solution contained 5% Polycose glucose polymers and 2% fructose. Both solutions contained similar amounts of sodium, potassium, calcium, magnesium, and chloride in the range suggested by the American College of Sports Medicine for rehydration solutions. Four hundred milliliters of each solution were administered to six male subjects and the amount of fluid emptied at 30 and 60 min by each subject was calculated. A non-absorbable dye, phenol red, was used to correct for gastric secretion. The gastric emptying of the 7% solution in healthy adult male subjects was not significantly different from the 5% solution or cold water. Inclusion of a polymerized form of glucose in a 7% glucose polymer-fructose solution can supply 70 g of carbohydrate per liter and also maximizes rehydration. This solution may be particularly useful in those activities where fluid and energy loss are particularly important.

Metabolic effects of heavy physical training on female 'age-group' swimmers.

Twelve female age-group swimmers and twelve female controls, aged ten to sixteen, performed a pre-training discontinuous maximal cycle ergometer test to determine the capacities of their anaerobic (alactacid and lactacid) and aerobic energy systems. Heart rate and oxygen uptake were determined during rest, exercise, and recovery. Blood samples were collected before and after exercise for determination of blood lactic acid concentrations. Tests were readministered to both groups immediately following the swimmers' competitive season. It was concluded that female swimmers possess significantly superior oxygen transport systems as compared to the untrained controls and that the high level of aerobic fitness is maintained throughout their training programme.

Metabolic responses to interval training programs of high and low power output.

The metabolic responses of 30 college-aged males were compared following high power (30-sec runs with 19 repetitions-Group HP) and low power (120-sec runs with 7 repetitions-Group LP) interval training programs (8-wk, 3 days/wk). Measurements included: maximal aerobic power (Vo2max, open circuit spirometry); maximal lactacid capacity (net-LAmax, blood LA accumulation following exhaustive exercise); net energy production (net Vo2 and netLA) following a 2-min run that was exhaustive before but not following training; and maximal muscular power (stair-climbing procedure). The results indicated: 1) significant but equal increases in Vo2 max in both groups; 2) no change in either group in netLAmax; 3) net Vo2 during the 2-min run was unchanged, however, netLA was significantly greater in Group LP; 4) no changes in either group in muscular power. It was concluded that low power and high power output interval training programs elicit similar changes in maximal aerobic and anaerobic metabolism, and that the physiological and or biochemical changes responsible for lowered lactic acid production during heavy, but submaximal exercise following training are produced to a greater extent by the low power program.

Oxygen cost during exercise in simulated subgravity environments.

Oxygen cost (VO2) and heart rate (HR) were determined during treadmill walking in simulated subgravity environments. The long axis of the subject's body was suspended parallel to the floor in a slow rotation room with feet aligned on the surface of a treadmill mounted 90 degrees on the wall. Without rotation, the subjects were virtually weightless against the treadmill; with centrifugation, environments of 0.25, 0.5 and 1 G were simulated. VO2 (open circuit) and HR (ECG) were measured during the 5th minute of walking at 3.2, 4.7 and 6.1 km/h. Similar measurements were also determined during walking at 1/2-G using the inclined plane technique. VO2 per unit mass and HR were significantly reduced in all subgravity environments. However, net VO2 per unit weight carried and, therefore, mechanical efficiency was found to be independent of gravity. This supports the idea that the most probable cause for the decreased O2 cost with reduced gravity is less body weight carried.

Frequency and duration of interval training programs and changes in aerobic power.

This study was designed to ascertain whether 7- and 13-wk interval training programs with training frequencies of 2 days/wk would produce improvement in maximal aerobic power (VO2max) comparable to that obtained from 7- and 13-wk programs of the same intensity consisting of 4 training days/wk. Sixty-nine young healthy college males were used as subjects. After training, there was a significant increase in VO2max (bicycle ergometer, open-circuit spirometry) that was independent of both training frequency and duration. However, there was a trend for greater gains after 13 wk. Maximal heart rate (direct lead ECG) was significantly decreased following training, being independent of both training frequency and duration. Submaximal VO2 did not change with training but submaximal heart rate decreased significantly with greater decreases the more frequent and longer the training. Within the limitations of this study, these results indicate that: 1) maximal stroke volume and/or maximal avO2 difference, principle determinants of VO2max, are not dependent on training frequency nor training duration, and 2) one benefit of more frequent and longer duration interval training is less circulatory stress as evidenced by decreased heart rate, during submaximal exercise.