Developing legally defensible physiological employment standards for prominent physically demanding public safety occupations: a Canadian perspective.

Canadian court decisions and human rights legislation impose strict legal criteria for developing applicant and incumbent physiological employment standards to qualify as a bona fide occupational requirement. These legal criteria compel researchers and employers to ensure that the standards are criterion-based and validly linked to the critical life threatening physically demanding tasks of the occupation, and this has led to the establishment of a systematic research process template to ensure this connection. Validation of job-related physiological employment standards is achieved using both construct and content procedures and reliability is established via test-retest procedures. The 1999 Supreme Court of Canada Meiorin Decision also obliges employers to demonstrate that it is impossible to accommodate an individual applicant or employee who is adversely impacted by lowering the physiological employment standards without imposing undue hardship on the employer. Recent evidence has demonstrated convincingly that familiarization opportunities, motivational feedback/coaching during test performance, and participation in a 6-week job-specific physical fitness training program can overcome the adverse impact of a physiological employment standards on a sub-group of participants, thereby providing "de facto" accommodation. In this article, the authors review the physiological employment standards for prominent Canadian physically demanding public safety occupations; police, correctional officers, nuclear emergency personnel, structural fire fighters, and wildland fire fighters, to illustrate the steps, challenges, and solutions involved in developing and implementing physiological employment standards designed to meet the requirements to qualify as a bona fide occupational requirement.

Physiological fitness and health adaptations from purposeful training using off-road vehicles.

The purpose of this study was to evaluate fitness and health adaptations from a training program riding all-terrain vehicles (ATV) and off-road motorcycles (ORM) as the exercise stimulus. Participants (n = 58) were randomized to a control group (n = 12) or one of four experimental groups; 2 days/week ATV (n = 11), 2 days/week ORM (n = 12), 4 days/week ATV (n = 11), or 4 days/week ORM (n = 12). Aerobic fitness, musculoskeletal fitness, body composition, clinical health, and quality of life (QOL) were compared at baseline and following 6 weeks of training. In all riding groups, there were improvements in blood pressure (SBP = 9.4 ± 10.1, DBP = 5.8 ± 6.2 mmHg), fasting glucose (0.5 ± 0.7 mmol/l), subcutaneous adiposity (0.9 ± 1.1%), body mass (0.7 ± 2.7 kg), waist circumference (1.3 ± 2.5 cm), and isometric leg endurance (26 ± 44 s). All changes were of moderate to large magnitude (Cohen's d 0.52-0.94) with the exception of a small loss of body mass (Cohen's d = 0.27). Although changes occurred in the riding groups for aerobic power (2.9 ± 4.6 ml kg(-1) min(-1)), leg power (172 ± 486 w), and curl-ups (13.2 ± 22.7), these changes were not significantly different from the control group. No significant alterations occurred in resting heart rate, trunk flexibility, back endurance, hand grip strength, long jump, pull/push strength, or push-up ability as a result of training. Physical domain QOL increased in all 2 days/week riders but mental domain QOL increased in all ORM, but not ATV riders regardless of volume. Ambient carbon monoxide levels while riding (<30 ppm) were within safe exposure guidelines. Positive adaptations can be gained from a training program using off-road vehicle riding as the exercise stimulus.

Fat oxidation rate and the exercise intensity that elicits maximal fat oxidation decreases with pubertal status in young male subjects.

The range of exercise intensities that elicit high fat oxidation rates (FOR) in youth and the influence of pubertal status on peak FOR are unknown. In a longitudinal design, we compared FOR over a range of exercise intensities in a small cohort of developing prepubertal male subjects. Five boys all at Tanner stage 1 (ages 11-12 yr) and nine men (ages 20-26 yr) underwent an incremental cycle ergometry test to volitional exhaustion. FOR curves were determined from indirect calorimetry during the final 30 s of each increment. The same protocol was duplicated annually in the boys as they progressed through puberty. The peak FOR was considerably higher (P<0.05) in boys at Tanner 1 (8.6+/-1.5 mg.kg lean body mass(-1).min(-1)) (mean+/-SD) compared with men (4.2+/-1.1 mg.kg lean body mass(-1).min(-1)). FOR dropped as boys developed through puberty (Tanner 2/3 peak rate=7.6+/-0.6 mg.kg lean body mass(-1).min(-1); Tanner 4 peak rate=5.4+/-1.8 mg.kg lean body mass(-1).min(-1), main effect of Tanner stage; P<0.05) to the levels found in men (not significant). The exercise intensity that elicited peak FOR was higher in the boys at Tanner 1 [56+/-6% peak aerobic power (VO2 peak)] than in men (31+/-4% VO2 peak) (P<0.001). This value tended to decrease by Tanner stage 4 (45+/-10% VO2 peak, main effect of Tanner stage; P=0.06). We conclude that, compared with men, prepubertal boys have higher relative FOR throughout a wide range of exercise intensities and that FOR drops as boys develop through puberty.

The 2004 Canadian recommendations for the management of hypertension: Part III--Lifestyle modifications to prevent and control hypertension.

OBJECTIVE: To provide updated, evidence-based recommendations regarding the role of lifestyle modification in the treatment and prevention of hypertension. OUTCOMES: Lifestyle modification interventions including exercise, weight reduction, alcohol consumption, dietary modification, intake of dietary cations and stress management are reviewed. Antioxidants and fish oil supplements are also reviewed, although specific recommendations cannot be made at present. EVIDENCE: MEDLINE searches were conducted from January 2002 to September 2003 to update the 2001 recommendations for the management of hypertension. Supplemental searches in the Cochrane Collaboration databases were also performed. Reference lists were scanned, experts were contacted, and the personal files of the subgroup members and authors were used to identify additional published studies. All relevant articles were reviewed and appraised independently using prespecified levels of evidence by content and methodology experts. RECOMMENDATIONS: Key recommendations include the following: lifestyle modification should be extended to nonhypertensive individuals who are at risk for developing high blood pressure; 30 min to 45 min of aerobic exercise should be performed on most days (four to five days) of the week; an ideal body weight (body mass index 18.5 kg/m2 to 24.9 kg/m2) should be maintained and weight loss strategies should use a multidisciplinary approach; alcohol consumption should be limited to two drinks or fewer per day, and weekly intake should not exceed 14 standard drinks for men and nine standard drinks for women; a reduced fat, low cholesterol diet that emphasizes fruits, vegetables and low fat dairy products, and maintains an adequate intake of potassium, magnesium and calcium, should be followed; salt intake should be restricted to 65 mmol/day to 100 mmol/day in hypertensive individuals and less than 100 mmol/day in normotensive individuals at high risk for developing hypertension; and stress management should be considered as an intervention in selected individuals. VALIDATION: All recommendations were graded according to the strength of the evidence and voted on by the Canadian Hypertension Education Program Evidence-Based Recommendations Task Force. Individuals with irreconcilable competing interests (declared by all members, compiled and circulated before the meeting) relative to any specific recommendation were excluded from voting on that recommendation. Only those recommendations achieving at least 70% consensus are reported here. These guidelines will continue to be updated annually.

Familial aggregation of 7-year changes in musculoskeletal fitness.

The purpose of this study was to determine the degree of familial resemblance in baseline and 7-year changes in musculoskeletal fitness. Data from the 1981 Canada Fitness Survey and the Campbell's Survey 7-year follow-up were used. The sample consisted of 1264 people (635 males and 629 females) between the ages of 7 and 69 years for whom measurements of musculoskeletal fitness were available at baseline. A subsample of 834 people had measurements at both baseline and 7-year follow-up. Sit-and-reach trunk flexibility, number of push-ups without time limit, number of sit-ups in 60 seconds, and hand-grip strength were used as indicators of musculoskeletal fitness. The data were adjusted for the effects of age and body mass index (and baseline level of the variable for changes) by using regression procedures, and they were standardized to zero mean and unit variance within each of the four sex-by-generation groups (fathers, mothers, sons, and daughters). Familial correlation models were fitted to the data by using the computer software SEGPATH. The results indicate significant familial resemblance for all indicators of musculoskeletal fitness for baseline measures and 7-year changes. The heritabilities, or the percentages of the total variance attributable to heredity, were 64% for trunk flexibility, 37% for push-ups, 59% for sit-ups, and 48% for grip strength. Similarly, heritabilities for the change scores were 48% for trunk flexibility, 52% for push-ups, 41% for sit-ups, and 32% for grip strength. The results suggest that familial, and perhaps genetic, factors are important in explaining the variance in musculoskeletal fitness not only cross-sectionally but also for changes over time.

Physical activity assessment options within the context of the Canadian Physical Activity, Fitness, and Lifestyle Appraisal.

The Canadian Physical Activity, Fitness, and Lifestyle Appraisal (CPAFLA) is a standardized battery of tests that is commonly used to assess asymptomatic individuals. This paper reviews evidence concerning the reliability, validity, and utility of the procedure currently used to assess habitual physical activity in the CPAFLA and surveys available physical activity assessment options. Special considerations related to age, gender, ethnicity, seasonal variations, and within-week variance are discussed. The potential assessment options are discussed with consideration given to the logistical and pragmatic constraints inherent in the CPAFLA. New technologies for future assessment of physical activity are briefly presented and recommendations for future research forwarded.

Cardiac performance in endurance-trained and moderately active young women.

PURPOSE: To compare the cardiac performance of endurance-trained (ET) and moderately active (MA) young women before exercise and throughout incremental work rates to maximum with particular interest in whether their stroke volume (SV) levels off at a submaximal work rate or increases to maximum. METHODS: Blood volume (BV), and exercise cardiac performance were examined in seven ET (VO2max = 64.3 +/- 2.0 mL.kg(-1).min(-1)) and seven MA (VO2max = 42.1 +/- 1.0 mL.kg(-1).min(-1)) women, aged 18-30 yr. Cardiac time intervals were measured at matched heart rates (HR). RESULTS: ET had a significantly larger BV than MA in both mL (ET = 5053 +/- 139, MA = 4327 +/- 202) and mL.kg(-1) (ET = 83.1 +/- 1.4, MA = 72.9 +/- 2.7). The SV of ET was significantly larger than the SV of MA throughout exercise, and the SV of ET increased progressively throughout incremental work rates to maximum. Although the SV of MA initially leveled off at a submaximal work rate, it underwent a secondary increase at very heavy work rates. Both diastolic filling rate (DFR) and left ventricular emptying rate (LVER) were significantly faster in ET compared with MA at HR of 150 bpm, 170 bpm and HRmax, and in both ET and MA, DFR was significantly faster than LVER at 170 bpm and HRmax. CONCLUSIONS: In young women, ET have a larger SV than MA due to an enhanced DFR and LVER, with the primary advantage being DFR (possibly due to their larger BV). In addition, the SV of ET increases progressively throughout incremental work rates to maximum with no plateau, whereas the SV of MA levels off through moderate to heavy work rates then undergoes a secondary increase at very heavy work rates.

Musculoskeletal fitness and health.

The purpose is to examine the relationship between musculoskeletal fitness and health status. Muscular strength is positively associated with independence and overall quality of life, and negatively associated with morbidity and potentially premature mortality. Muscular endurance is positively related to overall quality of life. Elevated muscular endurance may reduce the incidence of falling and its associated injuries. Muscular power is predictive of functional capacity, resultant disability, and potentially premature mortality. Flexibility is positively associated with mobility and independence. Women and the aged may be susceptible to musculoskeletal impairments leading to reduced health status and thus may represent primary target groups for intervention programs. High levels of musculoskeletal fitness are associated with positive health status, and low levels of musculoskeletal fitness are associated with lower health status.

Canadian musculoskeletal fitness norms.

The purpose of this report is to provide representative norms for measurements of musculoskeletal fitness (partial curl-ups, vertical jump, and leg power) for which Canadian norms are not currently available. Partial curl-ups, vertical jump, trunk flexion (sit and reach), grip strength, muscular endurance (push-ups), body mass index, and subcutaneous adiposity (sum of five skinfolds) were assessed, and leg power was calculated in 571 self-reportedly healthy participants (312 females and 259 males) aged 15-69 yr. The representativeness of the sample was confirmed by statistically comparing the fitness characteristics of the participants in the present study to those in the Canada Fitness Survey of 1981 and the Campbell's Survey of 1988. Normative data for partial curl-ups, vertical jump, and leg power were generated for males and females in six age groups (15-19, 20-29, 30-39, 40-49, 50-59, 60-69) for use in fitness appraisal protocols for the Canadian population.

Health-related fitness, physical activity, and history of back pain.

The relationship between history of back pain and measurements of both health-related fitness and physical activity participation was examined in 233 males and 287 females aged 15-69 years. Participants were divided by gender into those reporting no history (NH) or a history (H) of recurring back pain. Analysis of variance indicated that trunk flexion, back extensor endurance, and physical activity participation were significantly higher for NH and waist girth significantly lower for NH in both genders. In females, mean abdominal muscular endurance was significantly higher in NH. Forward stepwise discriminant function analyses indicated that the best discriminators between NH and H were back extensor endurance and physical activity participation in both genders and waist girth in females. These findings support using measurements of trunk flexion, abdominal muscular endurance, back extensor endurance, physical activity participation, and waist girth as indicators of back fitness in the evaluation of back health.

Health implications of musculoskeletal fitness.

Although it is well documented that physical activity participation can bring about improvements in musculoskeletal fitness, related health implications have only been substantiated in the elderly. Currently, interpretations of the results of musculoskeletal fitness appraisals for the general population are based largely on an intuitive belief that enhanced musculoskeletal fitness is associated with higher levels of health throughout adulthood. Musculoskeletal fitness was measured in 312 females and 259 males aged 15-69 years. Health levels were determined using two previously validated questionnaires and expressed as composite health scores derived from principal components analysis. Grip strength, push strength, pull strength, push-ups, and trunk forward flexion were significant predictors of health scores after controlling for the potentially confounding effects of gender age, aerobic fitness, waist circumference, and smoking status. These findings indicate that musculoskeletal fitness is related to health in males and females aged 15 to 69 years.

Blood volume, aerobic power, and endurance performance: potential ergogenic effect of volume loading.

OBJECTIVE: Blood volume (BV) and hemoglobin concentration ([Hb]) play important roles in oxygen transport. Manipulation of both BV and [Hb] can markedly affect systemic oxygen transport and maximal aerobic capacity (VO2max). However, the role of BV in oxygen transport and aerobic performance is not well understood. It has recently been postulated that an acute expansion of BV using plasma volume (PV), independent of changes in [Hb], may represent a potential ergogenic property. Therefore, the primary objective of this review was to determine the potential ergogenic properties of volume loading. DATA SOURCES: An extensive research of Medline and Sport-Discus along with cross-referencing was conducted. Articles were included on the basis of their relevancy to the purpose of this review. Only articles published in English were included in the analysis. STUDY SELECTION: All study designs using human participants were reviewed. DATA EXTRACTION: A systematic analysis of data regarding the effect of BV on the determination of oxygen transport, aerobic capacity, and endurance performance was conducted. Particular emphasis was given to articles that examined BV as the key independent variable. Articles relevant to the evaluation of the impact of BV on aerobic capacity and endurance performance were reviewed according to the strengths of the individual study designs. RESULTS: Seven investigations evaluated the impact of acute changes in BV, independent of changes in [Hb], on VO2max. Of these investigations, three revealed that acute manipulations of BV result in no change or a slight reduction in VO2max. Three investigations revealed a significant improvement in VO2max after acute PV expansion. One investigation revealed a nonsignificant increase in VO2max after acute PV expansion. Seven investigations evaluated the impact of acute changes in BV, independent of changes in [Hb], on endurance performance: two revealed a significant improvement in endurance performance after acute PV expansion, and five revealed an unchanged or reduced endurance performance after acute PV expansion. The majority of investigations showing an improvement in VO2max and/or endurance performance after acute PV expansion were conducted using untrained individuals. CONCLUSION: Volume loading does not result in an improvement in VO2max and/or endurance performance in endurance athletes. Volume loading in untrained individuals may improve VO2max, but does not bring these individuals to the aerobic capacity of endurance-trained athletes. Also, volume loading generally does not lead to improvement in endurance performance, irrespective of its effects on VO2max.

The economic burden of physical inactivity in Canada.

BACKGROUND: About two-thirds of Canadians are physically inactive. As a risk factor for several chronic diseases, physical inactivity can potentially be a substantial public health burden. We estimated the direct health care costs attributable to physical inactivity in Canada, the number of lives lost prematurely each year that are attributable to a sedentary lifestyle and the effect that a reduction of 10% in inactivity levels (a Canadian objective for 2003) could have on reducing direct health care costs. METHODS: We calculated summary relative risk (RR) estimates from prospective longitudinal studies of the effects of physical inactivity on coronary artery disease, stroke, colon cancer, breast cancer, type 2 diabetes mellitus and osteoporosis. We then computed the population-attributable fraction (PAF) for each illness from the summary RR and the prevalence of physical inactivity (i.e., 62%) and applied the PAF to the total direct health care expenditures for 1999 and to the number of deaths in 1995 associated with each disease to determine the health care costs and lives lost prematurely that were directly attributable to physical inactivity. RESULTS: About $2.1 billion, or 2.5% of the total direct health care costs in Canada, were attributable to physical inactivity in 1999. A sensitivity analysis (simultaneously varying each of the health care costs and PAF by +/- 20%) indicated that the costs could be as low as $1.4 billion and as high as $3.1 billion. About 21,000 lives were lost prematurely in 1995 because of inactivity. A 10% reduction in the prevalence of physical inactivity has the potential to reduce direct health care expenditures by $150 million a year. INTERPRETATION: Physical inactivity represents an important public health burden in Canada. Even modest reductions in inactivity levels could result in substantial cost savings.

Induced hypervolemia, cardiac function, VO2max, and performance of elite cyclists.

OBJECTIVE: To determine whether plasma volume expansion (PVexp) in elite endurance-trained (ET) cyclists, who already possess both a high blood volume (BV) and a high VO2max, leads to further enhancements in their cardiac function, VO2max, and endurance performance (time to exhaustion at 95% VO2max). METHODS: Nine male ET cyclists (V02max = 68.9 +/- 0.6 (SEM) mL x kg(-1) x min(-1)) were studied employing a double blind, cross-over design; i) before PVexp, ii) after sham PVexp (Sham), iii) after restoration of normocythemia, iv) after PVexp (6% dextran), and v) upon reestablishment of normocythemia. RESULTS: PVexp resulted in a 547 +/- 61 mL increase in BV (P < 0.05). Maximal cardiac output and maximal stroke volume were higher (P < 0.05) after PVexp, but the magnitude of these increases was only sufficient to counter the hemodilution effect (lowered O2 content) of PVexp, such that O2 transport, VO2max, and endurance performance remained unchanged. CONCLUSIONS: Expansion of BV in elite ET cyclists, who already possess a high BV, does not improve their VO2max and endurance performance. Elite ET athletes may already be at an optimal BV, which is at or near the limits of their diastolic reserve capacity.

Exercise cardiac function in young through elderly endurance trained women.

PURPOSE: To clarify the physiological reasons for the decline in aerobic power of endurance trained (ET) women with aging. METHODS: Blood volume, VO2max, and exercise cardiac function were examined in 23 ET women; six age 20-29 yr, six age 40-45 yr, six age 49-54 yr, and five age 58-63 yr. RESULTS: Blood volume was unchanged with aging. VO2max declined progressively at a rate of 0.51 mL x kg(-1) x min(-1) x yr(-1). During maximal exercise, there was an increase in total peripheral resistance (TPR) and a decrease in heart rate, stroke volume, and cardiac output with increasing age. At all ages, cardiac filling (diastole) was significantly faster than cardiac emptying (systole). Stroke volume did not plateau at a submaximal work rate but increased progressively to maximum. CONCLUSIONS: The decline in VO2max with age in ET women is due to decreases in maximal heart rate, stroke volume and cardiac output, and the primary advantage in the exercise cardiac performance of ET women of all ages is diastolic rather than systolic function.

Haemoglobin, blood volume, cardiac function, and aerobic power.

Alterations in [Hb], which are mediated through changes in arterial oxygen content, and alterations in BV, which are mediated through changes in cardiac output (Q), have a significant effect on both VO2max and aerobic performance. If BV is held constant, a decrease in [Hb] (anaemia) causes a decrease in VO2max and aerobic performance, while an increase in [Hb] (blood doping) causes an increase in VO2max and aerobic performance. If [Hb] is held constant, an increase in BV can cause and increase in both VO2max and aerobic performance, while a decrease in BV can cause a decrease in VO2max and aerobic performance. In addition, an increase in BV can compensate for moderate reductions in [Hb] through increase in Q, allowing VO2max to remain unchanged or even increase. Also, a large portion of the difference in the enhanced cardiovascular function of endurance athletes is due to their high BV and the resultant enhancement of diastolic function. Hence, optimizing both [Hb] and BV is a very important consideration for endurance performance.

Reproducibility of the acetylene rebreathe technique for determining cardiac output.

PURPOSE: The acetylene rebreathe technique is a well established method for the determination of cardiac output (Q) at rest and during exercise. We sought to demonstrate that the acetylene rebreathe technique allows for highly reproducible determinations of Q. METHODS: Nine elite male endurance cyclists (VO2max = 68.9 +/- 0.6 mL.kg-1.min-1) performed a modified acetylene rebreathe maneuver during incremental exercise on four repeat test days. A key modification to the method originally described by Grollman was the maintenance of a positive filling pressure during the inhalation portion of the procedure. RESULTS: There were no significant differences in determinations of Q at the same submaximal heart rates on four separate test days. The coefficient of variation for repeat determinations of maximal Q during the same work rate, expressed as the standard deviation of the difference between duplicate measurements, is 4.8%. The coefficient of variation for determinations of maximal Q at the same heart rate on different days, expressed as the standard deviation of the difference between four test days, is 2.6%. CONCLUSION: These findings illustrate that the acetylene rebreathe technique can be used with confidence to assess Q across repeated experimental days.

Exercise cardiac function in endurance-trained males versus females.

OBJECTIVE: To examine and compare the exercise cardiac function of endurance-trained (ET) women and men. PARTICIPANTS: Six ET women aged 20 to 29 years (mean VO2max = 64 ml.kg-1.min-1) and 9 ET men aged 20 to 29 years (mean VO2max = 69 ml.kg-1.min-1) were included in the study. MAIN OUTCOME MEASURES: Cardiac output (Q), stroke volume (SV), diastolic filling rate (DFR), and left ventricular ejection rate (LVER) were compared at rest and during exercise at heart rates (HRs) of 110, 130, 150, 170 bpm, and max. Resting blood volume (BV) and hemoglobin concentration ([Hb]) were also compared. RESULTS: Compared to women, men had a higher BV and [Hb]. At HRmax, men had a higher Q (31.0 +/- 0.6 versus 24.1 +/- 0.9 l.min-1), SV, DFR, and LVER than women. When expressed relative to body mass (kg), there were no gender differences in SVmax, and women had a significantly higher a-v DO2max (approximately 19%) than men. The SV of the men and women did not plateau at a submaximal level but continued to increase progressively to HRmax. During maximal exercise, the DFR was significantly faster than the LVER in the men and the women. CONCLUSIONS: When ET men and women are matched for body mass, the gender difference in SVmax is reduced so that it is no longer statistically significant. However, there are still significant gender differences in Q, DFR, LVER, BV, and [Hb] that contribute to a higher VO2max (ml.kg-1.min-1) in ET men compared to women. To augment SVmax, women and men rely to a greater extent on diastolic filling than on left ventricular emptying.

Effect of alterations in blood volume on cardiac function during maximal exercise.

Recently, we proposed that the higher stroke volume (SV) and cardiac output (Q) of endurance-trained (ETR) versus untrained (UTR) individuals are attributable primarily to the enhanced diastolic filling of ETR consequent to a larger blood volume (BV). To test this hypothesis, we examined the effects of manipulating BV on the cardiac function of six ETR and six UTR males. Both groups were examined in the control BV condition (BVctl), then ETR were examined immediately following a 500 mL reduction in BV (BVred) and UTR were examined immediately following a 500 mL expansion of BV (BVexp). In BVctl, compared with UTR, ETR had significantly greater BV (16%), maximal diastolic filling rate (47.4%), maximal ventricular emptying rate (24.6%), SVmax (31.6%), Qmax (29%) and VO2max (54.5%). Following BVexp in UTR, there were immediate significant increases in maximal diastolic filling rate (22.5%), SVmax (9.1%), Qmax (8.9%), and VO2max (12.7%). Following BVred in ETR there were immediate significant decreases in maximal diastolic filling rate (27%), SVmax (14.3%), Qmax (14.7%), and VO2max (7.0%). Maximal systolic emptying rate did not change significantly following BVred or BVexp. We conclude that changes in SV and Q consequent to alterations in BV are attributable primarily to changes in diastolic function, and the majority of the higher diastolic filling rate of ETR is due to their larger BV.