Shannon S. D. Bredin

Health benefits of physical activity: the evidence

The primary purpose of this narrative review was to evaluate the current literature and to provide further insight into the role physical inactivity plays in the development of chronic disease and premature death. We confirm that there is irrefutable evidence of the effectiveness of regular physical activity in the primary and secondary prevention of several chronic diseases (e.g., cardiovascular disease, diabetes, cancer, hypertension, obesity, depression and osteoporosis) and premature death. We also reveal that the current Health Canada physical activity guidelines are sufficient to elicit health benefits, especially in previously sedentary people. There appears to be a linear relation between physical activity and health status, such that a further increase in physical activity and fitness will lead to additional improvements in health status.

Prescribing exercise as preventive therapy

Energy expenditure of about 1000 kcal (4200 kJ) per week (equivalent to walking 1 hour 5 days a week) is associated with significant health benefits. Health benefits can be achieved through structured or nonstructured physical activity, accumulated throughout the day (even through short 10-minute bouts) on most days of the week. In this article we outline the means of evaluating cardiovascular and musculoskeletal fitness, the methods of evaluating physical activity levels, the current recommendations for exercise (including intensity, type, time and frequency) and the resources available for patients and physicians interested in learning more about the evaluation of physical activity and fitness levels and the prescription of exercise.

The health benefits of interactive video game exercise.

The purpose of this study was to evaluate the effectiveness of interactive video games (combined with stationary cycling) on health-related physical fitness and exercise adherence in comparison with traditional aerobic training (stationary cycling alone). College-aged males were stratified (aerobic fitness and body mass) and then assigned randomly to experimental (n = 7) or control (n = 7) conditions. Program attendance, health-related physical fitness (including maximal aerobic power (VO2 max), body composition, muscular strength, muscular power, and flexibility), and resting blood pressure were measured before and after training (60%-75% heart rate reserve, 3 d/week for 30 min/d for 6 weeks). There was a significant difference in the attendance of the interactive video game and traditional training groups (78% +/- 18% vs. 48% +/- 29%, respectively). VO2 max was significantly increased after interactive video game (11% +/- 5%) but not traditional (3% +/- 6%) training. There was a significantly greater reduction in resting systolic blood pressure after interactive video game (132 +/- 6 vs. 123 +/- 6 mmHg) than traditional (131 +/- 7 vs. 128 +/- 8 mmHg) training. There were no significant changes in body composition after either training program. Attendance mediated the relationships between condition and changes in health outcomes (including VO2 max, vertical jump, and systolic blood pressure). The present investigation indicates that a training program that links interactive video games to cycle exercise results in greater improvements in health-related physical fitness than that seen after traditional cycle exercise training. It appears that greater attendance, and thus a higher volume of physical activity, is the mechanism for the differences in health-related physical fitness.

The challenge of low physical activity during the school day: at recess, lunch and in physical education

Purpose To describe physical activity (PA) intensity across a school day and assess the percentage of girls and boys achieving recommended guidelines. Methods The authors measured PA via accelerometry in 380 children (8–11 years) and examined data representing (1) the whole school day, (2) regular class time, (3) recess, (4) lunch and (5) scheduled physical education (PE). Activity was categorised as sedentary (SED), light physical activity (LPA) or moderate to vigorous physical activity (MVPA) using age-specific thresholds. They examined sex differences across PA intensities during each time period and compliance with recommended guidelines. Results Girls accumulated less MVPA and more SED than boys throughout the school day (MVPA −10.6 min; SED +13.9 min) recess (MVPA −1.6 min; SED +1.7 min) and lunch (MVPA −3.1 min; SED +2.9 min). Girls accumulated less MVPA (−6.2 min), less LPA (−2.5 min) and more SED (+9.4 min) than boys during regular class time. Fewer girls than boys achieved PA guidelines during school (90.9% vs 96.2%), recess (15.7% vs 34.1%) and lunch (16.7% vs 37.4%). During PE, only 1.8% of girls and 2.9% of boys achieved the PA guidelines. Girls and boys accumulated similar amounts of MVPA, LPA and SED. Conclusion The MVPA deficit in girls was due to their sedentary behaviour as opposed to LPA. Physical activity strategies that target girls are essential to overcome this deficit. Only a very small percentage of children met physical activity guidelines during PE. There is a great need for additional training and emphasis on PA during PE. In addition schools should complement PE with PA models that increase PA opportunities across the school day.

Predicting the effect of interactive video bikes on exercise adherence: An efficacy trial

Exercise games that employ video game technology are increasing in the marketplace but have received scant research attention despite their popularity. The purpose of this study was to evaluate the effect of videobike gaming on the constructs of the theory of planned behavior (TPB) and adherence in comparison to a cycling condition where participants listen to self-selected music. Participants were 29 inactive young men assigned randomly to experimental (n = 16) or comparison (n = 13) conditions. The recommended training regime consisted of moderate intensity activity (60–75% heart rate reserve), 3 days/week for 30 min/day for 6 weeks. At the end of the first session, participants were asked to complete TPB measures and these were subsequently measured 6 weeks later. Attendance was used as the measure of adherence. Results showed that affective attitude and adherence across the 6 weeks significantly favored the videobike condition over the comparison condition. Regression analyses suggested partial mediation of the effect of the videobike condition on adherence via affective attitude. This is the first study to provide evidence that interactive videobikes may improve adherence over traditional cycling because the activity produces higher affective attitudes. The results are promising for expanding to community-based evaluation.

Pulse Decomposition Analysis of the digital arterial pulse during hemorrhage simulation

Background Markers of temporal changes in central blood volume are required to non-invasively detect hemorrhage and the onset of hemorrhagic shock. Recent work suggests that pulse pressure may be such a marker. A new approach to tracking blood pressure, and pulse pressure specifically is presented that is based on a new form of pulse pressure wave analysis called Pulse Decomposition Analysis (PDA). The premise of the PDA model is that the peripheral arterial pressure pulse is a superposition of five individual component pressure pulses, the first of which is due to the left ventricular ejection from the heart while the remaining component pressure pulses are reflections and re-reflections that originate from only two reflection sites within the central arteries. The hypothesis examined here is that the PDA parameter T13, the timing delay between the first and third component pulses, correlates with pulse pressure. T13 was monitored along with blood pressure, as determined by an automatic cuff and another continuous blood pressure monitor, during the course of lower body negative pressure (LBNP) sessions involving four stages, -15 mmHg, -30 mmHg, -45 mmHg, and -60 mmHg, in fifteen subjects (average age: 24.4 years, SD: 3.0 years; average height: 168.6 cm, SD: 8.0 cm; average weight: 64.0 kg, SD: 9.1 kg). Results Statistically significant correlations between T13 and pulse pressure as well as the ability of T13 to resolve the effects of different LBNP stages were established. Experimental T13 values were compared with predictions of the PDA model. These interventions resulted in pulse pressure changes of up to 7.8 mmHg (SE = 3.49 mmHg) as determined by the automatic cuff. Corresponding changes in T13 were a shortening by -72 milliseconds (SE = 4.17 milliseconds). In contrast to the other two methodologies, T13 was able to resolve the effects of the two least negative pressure stages with significance set at p < 0.01. Conclusions The agreement of observations and measurements provides a preliminary validation of the PDA model regarding the origin of the arterial pressure pulse reflections. The proposed physical picture of the PDA model is attractive because it identifies the contributions of distinct reflecting arterial tree components to the peripheral pressure pulse envelope. Since the importance of arterial pressure reflections to cardiovascular health is well known, the PDA pulse analysis could provide, beyond the tracking of blood pressure, an assessment tool of those reflections as well as the health of the sites that give rise to them.

The relationship between hypertension and obesity across different ethnicities.

Background and objective: Hypertension and obesity are major contributors to cardiovascular disease, and the relationship between these conditions is known to vary among ethnicities. However, this relationship has not previously been examined in aboriginal populations. The present investigation aimed to identify and compare this relationship among white (n = 3566), aboriginal (n = 850), East Asian (n = 446), and South Asian (n = 222) individuals from the province of British Columbia, Canada. Methods: Blood pressure, BMI, and waist circumference were directly measured along with self-reported antihypertensive medication usage. Relative risk ratios were calculated to evaluate the risk of hypertension among individuals of varying BMI and waist circumference measurements. The relative risks of hypertension were compared both within and between four ethnic groups. Results: Greater relative risks for hypertension were observed among individuals with increased BMI or increased waist circumference among all four ethnic groups. Aboriginal individuals appear to experience the greatest increases in relative risk for hypertension with increased BMI or waist circumference compared to other ethnic groups. The differences in the risk of developing hypertension between aboriginal and white populations appear to be largely associated with differences in body composition (i.e., BMI or waist circumference). East Asian and South Asian populations experience greater relative risk for hypertension than white populations at the same level of BMI or waist circumference. Conclusion: Hypertension prevention and treatment strategies among aboriginal, East Asian, and South Asian populations should target reducing fat mass and abdominal fat.

The 6-Minute Walk Test as a Predictor of Objectively Measured Aerobic Fitness in Healthy Working-Aged Adults

Abstract There is a paucity of research examining the 6-minute walk test (6MWT) in young to middle-aged healthy individuals, and little is known about the utility of the 6MWT for predicting aerobic fitness. Purpose: 1) To characterize the aerobic demand of the 6MWT in a group of healthy working-aged adults; 2) to examine the ability of the 6MWT to objectively differentiate the fitness level between participants; and 3) to create prediction equations for 6MWT distance and maximal oxygen consumption (VO2 max) using the 6MWT results in combination with easily measured anthropometric and demographic variables. Methods: Participants (N = 44; men, 23; women, 21) completed the 6MWT, VO2 max, and a battery of simple fitness measures. Results: The aerobic demand of the 6MWT was 28.7 ± 5.7 mL·kg-1·min-1 (72.7% ± 11.6% of VO2 max). Rank order correlation revealed a moderate strength association between 6MWT distance and VO2 max (r = 0.49; P = 0.001). Using stepwise multiple linear regression, we were able to account for 72.4% of the variance in VO2 max using the 6MWT when combined with participant body weight, sex, resting heart rate (HR), and age according to the following equation: VO2 max (mL · kg-1 · min-1) = 70.161 + (0.023 × 6MWT [m]) - (0.276 × weight [kg]) - (6.79 × sex, where m = 0, f = 1) - (0.193 × resting HR [beats per minute]) - (0.191 × age [y]). Conclusion: The 6MWT is of moderate-to-vigorous intensity, and may be useful in the classification of aerobic fitness, which is associated with health outcomes. Inclusion of further patient characteristics greatly increases the predictive value of the 6MWT for estimating VO2 max, which has important implications for those seeking a noninvasive and simple-to-use determinant of maximal aerobic power.

Metabolic Requirements of Interactive Video Game Cycling

BACKGROUND Interactive video game exercise leads to improved exercise adherence and health-related physical fitness in comparison to traditional stationary cycling. It has been postulated that interactive video game exercise has greater metabolic requirements than traditional cycling; however, this has not been tested to date. PURPOSE To examine the metabolic requirements of interactive video game exercise in comparison to traditional stationary cycling at matched incremental workloads. METHODS Fourteen participants (seven males and seven females) were examined during three separate sessions: 1) incremental cycle ergometer exercise for the assessment of maximal aerobic power and peak workload; 2) traditional cycling on a cycle ergometer using 5-min constant workloads of 25%, 50%, and 75% of maximal power output; and 3) cycling using identical constant, relative workloads while playing interactive video games. Measurements of oxygen consumption, heart rate, and rating of perceived exertion were assessed throughout. RESULTS During interactive video game exercise, steady-state heart rate (26% +/- 18% and 14% +/- 13%), energy expenditure (61% +/- 41% and 25% +/- 21%), and oxygen consumption (34% +/- 17% and 18% +/- 12%) were significantly higher at the constant submaximal workloads of 25% and 50%, respectively. There was no significant difference in rating of perceived exertion between conditions at any workload. CONCLUSIONS Interactive video game cycling results in greater metabolic requirements (despite similar perceptions of exertion) at submaximal constant workloads than traditional cycling. This form of training may be a novel and an attractive intervention in the battle against physical inactivity and associated health complications.

Aortic stiffness increased in spinal cord injury when matched for physical activity.

PURPOSE The objective of this study is to compare arterial stiffness between those with spinal cord injury (SCI) and able-bodied (AB) individuals when matched for habitual level of physical activity. METHODS A total of 17 SCI and 17 AB individuals were matched for sex, age, weight, blood pressure, and levels of self-reported habitual physical activity (Godin-Shephard). Measures included central pulse wave velocity (PWV) (carotid-femoral PWV (cfPWV)) and lower limb PWV (femoral--toe PWV(ftPWV)) as well as large and small arterial compliance. RESULTS The cfPWV was significantly elevated (7.3 ± 2.1 vs. 5.7 ± 1.4 m·s, P < 0.05) in SCI compared with AB. No other measures of arterial stiffness were different between the groups. Moderate to vigorous physical activity was significantly correlated with both large (r = 0.48, P < 0.05) and small (r = 0.65, P < 0.01) artery compliance, but not cfPWV or ftPWV. CONCLUSIONS Both large and small artery compliance appear to be associated with habitual physical activity in physically active individuals with SCI. However, we did not show that physical activity is associated with PWV in physically active individuals with SCI. These findings suggest that factors other than physical inactivity may mediate the increase in arterial stiffness widely reported in the SCI population.