Scott G. Thomas

Effect of television viewing at mealtime on food intake after a glucose preload in boys.

Television viewing (TVV) is considered a contributing factor to the development of childhood obesity yet it is unclear whether obesity results, in part, from increased energy intake during TVV. The objective of this study was to determine the effect of TVV on food intake (FI) of boys at a meal and its effect on caloric compensation at the test meal after a premeal glucose drink. On four separate mornings and in random order, boys received equally sweetened preloads containing Splenda sucralose or glucose [1.0 g/kg body weight (BW)] in 250 mL of water 2 h after a standard breakfast. Food intake from a pizza meal was measured 30 min later with or without TVV. Both preload treatment (p < 0.01) and TVV (p < 0.001) affected FI (kcal). TVV increased lunchtime FI by an average of 228 kcal. Glucose suppressed FI in the no TVV condition compared with control, but the effect was not statistically significant during TVV. Body composition and subjective appetite scores were positively associated with FI at the test lunch. In conclusion, TVV while eating a meal contributes to increased energy intake by delaying normal mealtime satiation and reducing satiety signals from previously consumed foods.

Potential markers of heavy training in highly trained distance runners.

Markers of a heavy increase in training were examined in ten highly trained distance runners (mean(s.d.) age 29.8(1.7) years, maximal oxygen intake 65.3 ml kg-1 min-1, personal best 10-km time 31 min 4 s) who undertook a deliberate 38% increment of training over a 3-week period. Their running performance did not improve, and six of the ten subjects developed sustained fatigue, suggesting that training was excessive, although the full clinical picture of overtraining did not develop. The Profile of Mood States was the best single marker of disturbed function, indicating increased fatigue and decreased vigour. There were no useful changes of resting heart rate or perceived exertion during submaximal running, sleep was undisturbed, and there were no orthopaedic injuries. Two subjects developed rhinoviral infections following the heavy training, and a third complained of symptoms that were diagnosed 2 weeks later as exercise-induced asthma. The increase of serum cortisol normally induced by 30 min of submaximal exercise was no longer seen when the same acute exercise was performed after heavy training. Resting lymphocyte proliferation tended to increase in response to phytohaematoglutinin (PHA) and concanavalin A (Con A), the ratio of helper to suppressor cells (H/S) decreased, and pokeweed mitogen induced smaller increases in IgG and IgM synthesis. Whereas before heavy training, PHA-stimulated lymphocyte proliferation was unchanged by 30 min of acute submaximal exercise, after 3 weeks of heavy training the same bout of exercise caused an 18% suppression of proliferation. Likewise, heavy training brought about a decrease of T-lymphocytes in response to acute submaximal exercise, but an abolition of the acute exercise-induced decrease in the H/S ratio. The previously observed exercise-induced decrease of IgG synthesis did not occur when the same acute bout of exercise was performed after heavy training. We conclude that such minor and transient changes of immune function may possibly be a warning that training is becoming excessive, but they have only a limited significance for overall immune function.

Effects of an Aerobic Exercise Program on Aerobic Capacity, Spatiotemporal Gait Parameters, and Functional Capacity in Subacute Stroke

Background and objective. In spite of the challenges, engaging in exercise programs very early after stroke may positively influence aerobic capacity and stroke-related outcomes, including walking ability. The objective of this study was to evaluate the feasibility of adding aerobic cycle ergometer training to conventional rehabilitation early after stroke and to determine effects on aerobic capacity, walking ability, and health-related quality of life. Methods. A prospective matched control design was used. All participants performed a graded maximal exercise test on a semi-recumbent cycle ergometer, spatiotemporal gait assessments, 6-Minute Walk Test, and Stroke Impact Scale. The Exercise group added 30 minutes of aerobic cycle ergometry to conventional inpatient rehabilitation 3 days/week until discharge; the Control group received conventional rehabilitation only. Results. All Exercise participants (n = 23) completed the training without adverse effects. In the 18 matched pairs, both groups demonstrated improvements over time with a trend toward greater aerobic benefit in the Exercise group with 13% and 23% increases in peak VO2 and work rate respectively, compared to 8% and 16% in the Control group (group-time interaction P = .71 and .62). A similar trend toward improved 6-Minute Walk Test distance (Exercise 53% vs Controls 23%, P = .23) was observed. Conclusion. Early aerobic training can be safely implemented without deleterious effects on stroke rehabilitation. A trend toward greater improvement in aerobic capacity and walking capacity suggests that such training may have an early beneficial effect and should be considered for inclusion in rehabilitation programs.

Quantitating the capillary supply and the response to resistance training in older men

Abstract Resistance training (RT) has been shown to increase aerobic power in older humans. To determine the effects of RT on the capillary supply in this population, nine older men (65–74 y) engaged in 9 weeks RT of the lower body. Following RT, peak O2 uptake (V.O2,peak) increased by 7% (P<.01). Needle biopsies (vastus lateralis muscle) revealed significant increases (mean ± SE) in fibre area (3,874 ± 314 μm2 to 4,778 ± 309 μm2), fibre perimeter (P, 262 ± 11 μm to 296 ± 11 μm), capillary contacts (3.7 ± .2 to 4.3 ± .3) and the individual capillary-to-fibre ratio (C:Fi, 1.33 ± .32 to 1.61 ± .37, P<.005). To evaluate the potential for blood-tissue exchange, both fibre area-based and perimeter-based measures of the capillary supply were compared. While the area-based measures were maintained, C:Fi/P was increased, consistent with an increase in the size of the fibre-capillary interface and thus, an increased potential for oxygen flux following RT. Of the measurements of capillary supply, V.O2,peak correlated best with C:Fi/P (r = 0.69, P<.005). These results indicate a significant increase in the capillary supply relative to the perimeter, but not the cross-sectional area, of the muscle fibres following RT in older men, and that C:Fi/P is strongly correlated to the V.O2,peak in this population.

Aerobic and Resistance Training in Coronary Disease: Single versus Multiple Sets

PURPOSE The purpose of this study was to compare resistance training (RT) (one set vs three sets) combined with aerobic training (AT) versus AT alone in persons with coronary artery disease. METHODS Subjects (n = 72) were randomized to AT (5 d x wk(-1)) or combined AT (3 d x wk(-1)) with either one set (AT/RT1) or three sets (AT/RT3) of RT performed 2 d x wk(-1). VO2peak, ventilatory anaerobic threshold (VAT), strength and endurance, body composition, and adherence were measured before and after 29 wk of training. RESULTS Fifty-three subjects (mean +/- SEM age 61 +/- 2) completed the training. The increase from baseline in VO2peak (L x min(-1)) averaged 11% for AT (P < 0.05), 14% for AT/RT1 (P < 0.01), and 18% for AT/RT3 (P < 0.001), however, the difference between groups was not significant. VAT improved significantly in the AT/RT3 group only (P < 0.05). The AT/RT3 group gained more lean mass than the AT group (1.5 versus 0.4 kg, P < 0.01), yet gains between AT/RT1 and AT were similar (P = 0.2). Only AT + RT groups demonstrated a reduction in body fat (P < 0.05). Strength and endurance increased more in the AT + RT groups than AT alone (P < 0.05). Adherence to number of sets performed was lower in AT/RT3 than AT/RT1 (P < 0.02). CONCLUSIONS Combined AT + RT yields more pronounced physiological adaptations than AT alone and appears to be superior in producing improvements in VO2peak, muscular strength and endurance, and body composition. The data support the use of multiple set RT for patients desiring an increased RT stimulus which may further augment parameters that affect VO2peak, VAT, lower body endurance, and muscle mass in a cardiac population.

The Canadian Home Fitness Test. 1991 update

The Canadian Home Fitness Test (CHFT) was developed in the mid-1970s (Bailey et al. 1974. 1976) as a simple home tool for the screening of fitness. Subjects were encouraged to climb and descend the domestic staircase at an age and sex-specific rate set by the music from a long-playing gramophone or tape recording, and to make an approximate classification of their fitness status from the attained speed of stepping and the immediate recovery heart rate. It was reasoned that the initial testing (with associated recommendations on an appropriate exercise prescription) should create an awareness of fitness, and that gains of fitness seen at repetition of the test might help to sustain an interest in exercise, Because of the simplicity of the test protocol. many Canadian investigators believed that the procedure had potential for the field-testing of cardiorespiratory fitness, and on this basis it became one element of the Canadian Standard Test of Fitness (CSFT) [Fitness Canada 1986], with subjects climbing standardised double 8-inch (20.3cm) steps, and heart rates being counted more precisely by electrocardiogram or observer palpation. In this modified format, the CHFT was used in a large survey of occupational fitness (Canadian Public Health Association 1979), in the Canada Fitness Survey of 1981 (Canadian Fitness and Lifestyle Institute 1983; Shephard 1986) and in surveys of Canadian Forces personnel (Bell & Allen 1983; CF Expres 1983). Early criticisms of the procedure on counts of safety, lack of precision in speed of the recorded music, difficulties in maintaining the stepping rhythm or counting the recovery heart rate accurately were considered and answered in a comprehensive review of the test (Shephard 1980). Practical evidence of the value of the CHFT concept is that several individuals have since marketed music-paced fitness tests, apparently without acknowledgement of prior Canadian work. The present paper considers new information on the safety, motivational value and accuracy of the CHFT.

Autonomic Regulation of the Circulation During Exercise and Heat Exposure Inferences from Heart Rate Variability

Minimal information is available on the autonomic response to exercise under adverse environmental conditions. Traditionally, pharmacological blockade has been used to study autonomic responsiveness but, owing to its invasive nature, such studies have been limited in their scope. Recent advances in electrocardiographic tape recording, telemetry and associated computing systems have provided investigators with noninvasive methods for assessing the autonomic response to various physiological stressors. This article describes methods for the analysis of heart rate variability (HRV) and discusses the reports of those who have used HRV analysis to evaluate autonomic regulation during exercise, heat exposure and the combination of these 2 stressors.Spectral analysis of HRV reduces variations in the R-R interval into component sine waves of differing amplitude and frequency. Amplitude (variance) is displayed as a function of frequency, and power (cumulative variance) is calculated for specified frequency ranges (<0.03Hz, 0.03 to 0.15Hz and 0.15 to 0.5Hz). Parasympathetic nervous system activity can be inferred from the several indices of high frequency power; however, the estimation of sympathetic nervous system activity from low frequency power is more problematic.Data on HRV have shown that sympathovagal regulation during exercise is dependent on the intensity of the activity and the environmental conditions. At the onset of exercise, heart rate is increased by a reduction in vagal tone and a temporary increase in sympathetic tone. A continuation of physical activity is associated with a continued withdrawal of vagal activity and an attenuation of sympathetic nervous system tone. However, with the additional stimulus of a heated environment, sympathetic activity remains increased throughout exercise.

Systems Modelling of the Relationship Between Training and Performance

Mathematical models may provide a method of describing and predicting the effect of training on performance. The current models attempt to describe the effects of single or multiple bouts of exercise on the performance of a specific task on a given day. These models suggest that any training session increases fitness and provokes a fatigue response. Various methods of quantifying the training stimulus (training impulse, absolute work, psychophysiological rating) and physical performance (criterion scale, arbitrary units) are employed in these models. The models are empirical descriptions and do not use current knowledge regarding the specificity of training adaptations. Tests of these models with published data indicate discrepancies between the predicted and measured time course of physiological adaptations, and between the predicted and measured performance responses to training. The relationship between these models and the underlying physiology requires clarification. New functional models that incorporate specificity of training and known physiology are required to enhance our ability to guide athletic training, rehabilitation and research.

Effects of exercise on cravings to smoke: The role of exercise intensity and cortisol

Abstract Research consistently demonstrates that a bout of moderate exercise alleviates cravings to smoke among abstaining smokers. The aims of this study were to examine whether doses of exercise (moderate or vigorous) reduced cravings differently, and whether reductions in cravings were associated with changes in cortisol concentration. Using a within-participant, crossover design, 18 participants conducted three 15-min treatment sessions on separate days: passive, walking (45–50% heart rate reserve), and running (80–85% heart rate reserve) conditions. Participants rated cravings at baseline, mid-treatment, and 0, 10, 20, and 30 min after each treatment. Salivary cortisol samples were collected at baseline, immediately after, and 30 min after each condition. Significant group × time interactions were identified, demonstrating significant reductions in craving items after the walking and running conditions compared with the passive control. No significant differences in craving reductions were found between walking and running conditions. Post hoc comparisons found that running condition cravings to smoke scores were reduced for a longer duration post-treatment than post-walking condition scores. The decline in cortisol concentration was attenuated in the running group only. Vigorous exercise has a similar effect to moderate exercise in terms of the magnitude of craving reduction. However, performing bouts of moderate-intensity exercise may be a better recommendation for reducing cravings.

The effect of duration of exercise at the ventilation threshold on subjective appetite and short-term food intake in 9 to 14 year old boys and girls

BackgroundThe effect of exercise on subjective appetite and short-term food intake has received little investigation in children. Despite a lack of reported evaluation of short-duration activity programs, they are currently being implemented in schools as a means to benefit energy balance. The purpose of this study was to determine the effect of duration of exercise at the ventilation threshold (VeT) on subjective appetite and short-term food intake in normal weight boys and girls aged 9 to 14 years.MethodsOn 4 separate mornings and in random order, boys (n = 14) and girls (n = 15) completed 2 rest or 2 exercise treatments for 15 (short-duration; SD) or 45 min (long-duration; LD) at their previously measured VeT, 2 h after a standardized breakfast. Subjective appetite was measured at regular intervals during the study sessions and food intake from a pizza meal was measured 30 min after rest or exercise.ResultsAn increase in average appetite, desire to eat, and hunger (p < 0.05) was attenuated by SD exercise, but was further increased (p < 0.05) by LD exercise. However, food intake after SD and LD exercise was similar to after rest in both boys and girls (p = 0.55). The energy cost of SD and LD exercise resulted in a lower net energy balance compared to resting during the study measurement period in boys (SD: Δ = -418 ± 301 kJ; LD: Δ = -928 ± 196 kJ) and in girls (SD: Δ = -297 ± 105 kJ; LD: Δ = -432 ± 115 kJ).ConclusionNeither SD nor LD exercise at the VeT increased short-term food intake and SD exercise attenuated increases in appetite. Thus, SD exercise programs in schools may be an effective strategy for maintaining healthier body weights in children.