Effects of lifestyle activity vs structured aerobic exercise in obese women: a randomized trial.

CONTEXT: Physical inactivity contributes to weight gain, but only 22% of Americans are regularly active. OBJECTIVE: To examine short- and long-term changes in weight, body composition, and cardiovascular risk profiles produced by diet combined with either structured aerobic exercise or moderate-intensity lifestyle activity. DESIGN: Sixteen-week randomized controlled trial with 1-year follow-up, conducted from August 1995 to December 1996. PARTICIPANTS AND SETTING: Forty obese women (mean body mass index [weight in kilograms divided by the square of height in meters], 32.9 kg/m2; mean weight, 89.2 kg) with a mean age of 42.9 years (range, 21-60 years) seen in a university-based weight management program. INTERVENTIONS: Structured aerobic exercise or moderate lifestyle activity; low-fat diet of about 1200 kcal/d. MAIN OUTCOME MEASURES: Changes in body weight, body composition, cardiovascular risk profiles, and physical fitness at 16 weeks and at 1 year. RESULTS: Mean (SD) weight losses during the 16-week treatment program were 8.3 (3.8) kg for the aerobic group and 7.9 (4.2) kg for the lifestyle group (within groups, P<.001; between groups, P = .08). The aerobic group lost significantly less fat-free mass (0.5 [1.3] kg) than the lifestyle group (1.4 [1.3] kg; P = .03). During the 1-year follow-up, the aerobic group regained 1.6 [5.5] kg, while the lifestyle group regained 0.08 (4.6) kg. At week 16, serum triglyceride levels and total cholesterol levels were reduced significantly (P<.001) from baseline (16.3% and 10.1% reductions, respectively) but did not differ significantly between groups and were not different from baseline or between groups at week 68. CONCLUSIONS: A program of diet plus lifestyle activity may offer similar health benefits and be a suitable alternative to diet plus structured aerobic activity for obese women.

Effects of weight loss and exercise training on natural killer cell activity in obese women.

PURPOSE: The purposes of this study were two-fold: (1) to evaluate the effects of an 8-wk weight loss program on natural killer (NK) cell activity in obese women and 2) to determine whether an additional program of combined aerobic and resistance exercise training modified the effects of caloric restriction on immune function. METHODS: Twenty-two healthy obese women with a mean weight of 96.9 +/- 14 kg and age of 38 +/- 7 yr were randomly assigned to diet-alone (D) or diet-plus-exercise training (D + EX) conditions. Subjects consumed 950 kcal.d-1 using prepackaged portion-controlled foods. Subjects in the D + EX group participated 3 times.wk-1 in a supervised program of light-to moderate-intensity aerobic activity and resistance training. Data were analyzed using a repeated measures ANOVA. RESULTS: After 8 wk of treatment, body weight decreased significantly in both groups (10.8% in D vs 11.4% in D + EX), whereas absolute and relative VO2peak increased in only D + EX (12.3% in D vs 57.7% in D + EX). Both groups experienced significant decreases in peripheral blood leukocytes and lymphocytes, although cell numbers remained within clinically normal range at week 8. NK cell (CD56+) proportion was unchanged in both groups after weight loss. The proportion of peripheral mononuclear cells expressing the interleukin-2 receptor-alpha (IL-2R alpha) (CD25+) decreased significantly (25.2%) in D and was unchanged in D + EX, resulting in a significant difference between groups at week 8. NK cell cytotoxicity was suppressed in D and unchanged in D + EX after treatment. Changes in NK cell activity were significantly correlated with proportional changes in (CD25+) (r = 0.584, P = 0.022), but not CD56+. CONCLUSIONS: A combined program of light- to moderate-intensity aerobic and resistance exercise offsets the apparent decrement in NK cell activity associated with weight loss.

Applied physiology of ice hockey.

Today's elite hockey players are physically bigger and have improved levels of physiological fitness when compared with their predecessors. Correspondingly, previous ice hockey studies that have become widely referenced may have little relevance to current players and the way the game is presently played. A great need exists to apply exercise science to the game of ice hockey. Although much has been written about the physiology of ice hockey, there is little information based on well controlled studies. Particularly, there is a paucity of knowledge concerning optimal training schedules, training specificity, recovery profiles and seasonal detraining. Moreover, the reports that do exist have attempted to make comparisons across all levels of skill and talent. Thus, fundamental questions remain as to actual physiological exercise response and specialised training programmes for ice hockey players, particularly at the elite level. There is a demand for new properly designed experiments to find answers pertaining to the appropriate training methods for today's ice hockey players. Future research directions should consider the relationships between performance and such variables as neuromuscular skills, strength, power, peripheral adaptations, travel, hydration, detraining and sport-specific training programmes. Incidence and severity of injury among ice hockey players in relation to fatigue and fitness must also be investigated. Much of the information currently used in ice hockey will remain speculative and anecdotal until these studies are conducted.

Application of impedance cardiography during exercise.

Impedance cardiography has been used over the last 30 years to measure stroke volume on a beat-by-beat basis. Cardiac output has been successfully measured with either upper or lower body exercise during light or moderate workloads. With strenuous exercise, movement artifacts severely limit the acquisition of a quality impedance cardiogram. Advances in computer technology and signal conditioning techniques have created the next generation of impedance cardiograph systems. The purpose of this study was to evaluate such a system, the noninvasive continuous cardiac output monitor (NCCOM3-R7), at rest and during submaximal upright cycle exercise. In addition, the relationships between thoracic impedance (Z(o)), first derivative of the change in thoracic impedance (dZ/dt) and posture were evaluated using the NCCOM3-R7 and the Minnesota impedance cardiograph 304B (MIC). Twenty-eight healthy men and women participated. The Z(o) progressively increased when moving from the supine to seated to standing position with both instruments. However, the NCCOM3-R7 yielded lower Z(o) values and higher dZ/dt values compared with the MIC for all postures. Z(o) and dZ/dt values appear to be dependent upon factors such as posture, gender, electrical current, and characteristics of the instrumentation. Exercise cardiac output values seemed reasonable for most subjects, although population subsets exist where the accuracy must be questioned. The general consensus supported by the impedance literature and reaffirmed by the present observations is that impedance cardiography provides a reasonable estimate of the directional changes in stroke volume and cardiac output during exercise and can be used to monitor changes in thoracic fluid balance. As this technology evolves and is further refined, it will undoubtedly play an increasing role in environmental medicine, exercise stress testing, cardiac rehabilitation, and sports medicine.

Immune responses and increased training of the elite athlete.

Ten elite male runners (age, 29.8 +/- 1.7 yr; maximum oxygen consumption, 65.3 +/- 4.9 ml.kg-1.min-1; 10-km times, 31 min 43 s +/- 1 min 46 s) deliberately increased training schedules by an average of 38% for 3 wk. Resting heart rate and maximal oxygen intake were unchanged, but the heart rate response to acute exercise was decreased. Following heavy training, blood samples taken at rest showed trends to a decreased helper/suppressor cell ratio, an increased phytohemagglutinin (PHA)- and concanavalin (ConA)-stimulated lymphocyte proliferation, and a decreased production of immunoglobulins IgG and IgM. Whereas PHA-stimulated lymphocyte proliferation was initially unchanged by acute exercise, after 3 wk of heavy training the same acute exercise caused an 18% suppression of proliferation. Acute exercise following heavy training did not alter pokeweed-stimulated IgG or IgM synthesis. There was no correlation between changes in lymphocyte subpopulations, helper/suppressor ratios, and mitogen-induced cellular proliferation. The immune system of endurance-trained athletes at rest seemed to tolerate the stress of heavy training, but superimposition of a bout of acute exercise on the chronic stress of heavy training resulted in immunosuppression, which was transient and most likely not of clinical significance.

Physical activity and the immune system.

Methods of examining immune function include a charting of susceptibility to infections, differential blood counts or lymphocyte counts, and measures of cell proliferation and immunoglobulin synthesis in response to external mitogens. The reported acute response to exercise is transient and quite variable, depending upon the type of exercise, the immunological methodology used, the intensity of effort relative to the fitness of the individual, and the timing of observation. A leucocytosis, a granulocytosis, a small lymphocytosis, and a decrease in the proportion of T to B cells reflect mainly changes of blood volume, demargination, and migration of cells. Lymphocyte subsets show a decreased helper/suppressor cell ratio and an increase of natural killer cells. Because of the lymphocytosis, mitogens induce an increased overall cell proliferation, but proliferation for a given number of cells is decreased. Prolonged exercise leads to a decrease of serum and salivary immunoglobulin levels. Soluble factors such as interleukin-1 and interferon are increased by a bout of exercise. Cross-sectional comparisons and training experiments suggest that under resting conditions well-conditioned individuals show some lymphocytosis, increased natural killer cell activity, higher levels of interleukin-1, and possibly an enhanced reaction to mitogens. Moderate training does not greatly change exercise responses at a given fraction of maximal effort. Excessive training suppresses immune function, but the changes are small, variable, and thus difficult to relate to overtraining. Moreover, because of their transient nature, they have only a limited influence upon the risks of infection or cancer.

Physiological profiles of the Canadian National Judo Team.

The physiology of Canadian National Judo Team members is described. These athletes differed widely in body size (height 157.4-187.7 cm; mass 56.5-100.8 kg). Aerobic fitness (treadmill) was high (VO2max = 4.49 I.min-1; 59.2 mL.kg-I.min-I), but relative VO2max decreased with increasing body mass. Elite judoka of other nations (Australia, 53.2; Poland, 59.0; Norway, 58.5) had comparable aerobic fitness. Significant (p less than 0.05) correlations between upper- (arm cranking, PWC170) versus lower-body aerobic fitness (r = 0.48), and upper- versus lower-body anaerobic power (r = 0.89) and capacity (r = 0.88) (Wingate) were observed. Peak power output (AnPP = 9.3 W.kg-I) and anaerobic capacity (AnCap = 260 J.kg-I) during arm cranking averaged 80% of leg-cranking values (AnPP = 13.7 W.kg-I; AnCap = 320 J.kg-I). Upper-body strength (bench press, one repetition, maximum = 100 kg) was also associated with upper-body anaerobic power (r = 0.72). Judoka exhibit a high degree of aerobic and anaerobic conditioning, and a pattern of total body fitness that is specifically required for their sport.