Physical training in the fire station and firefighters' cardiovascular health.

BACKGROUND: Few fire departments in Québec have a diversified health promotion programme. Yet, many allow firefighters to physically train during working hours. AIMS: To compare the weekly physical activity (PA) level and cardiovascular health indicators of firefighters who physically train on duty to those who do not. METHODS: Participants underwent a cardiovascular health assessment and completed an online questionnaire. RESULTS: One hundred and five full-time male firefighters participated in the study. Two groups were formed: firefighters who physically train while on duty (E, n = 64) and firefighters who do not (NoE, n = 41). Following statistical adjustments, off-duty weekly PA was not different between the two groups (E: 239 ± 224 versus NoE: 269 ± 249 min, P = 0.496); however, total weekly PA was higher (P = 0.035) in E (381 ± 288 min) than in NoE (274 ± 200 min). A difference was also observed in obesity prevalence measured with waist circumference (E: 9% versus NoE: 27%, P = 0.026) and in physical inactivity prevalence (E: 0% versus NoE: 27%, P < 0.001). After statistical adjustments, E firefighters have a significantly lower waist-to-height ratio than NoE firefighters (E: 0.51 ± 0.05 versus NoE: 0.54 ± 0.05, P = 0.017). CONCLUSIONS: Results show that firefighters who physically train while on duty have a higher total PA level on a weekly basis and have better cardiovascular health indicators. Our findings suggest that fire services should promote physical training while on duty to improve firefighters' cardiovascular health.

Cardiovascular disease risk in female firefighters.

BACKGROUND: Female firefighters are in the minority in the Québec firefighter population and worldwide. To our knowledge, no study has focused on cardiovascular risk factors in female firefighters, and further research in this area is needed to evaluate and reduce the risk of on-duty sudden cardiac death. AIMS: To evaluate the prevalence of cardiovascular disease (CVD) risk factors in female firefighters in Québec. METHODS: A cross-sectional study using an online questionnaire to evaluate lifestyle and CVD risk factors and symptoms. RESULTS: Forty-one female firefighters (age: 38.2 ± 9.9 years) participated in this study, representing ~7% of all female Québec firefighters. The prevalence of obesity (body mass index ≥ 30 kg/m2), hypertension, dyslipidaemia, type 2 diabetes mellitus, smoking and physical inactivity was 12% (95% confidence interval [CI] 4-26%), 5% (95% CI 0.6-19%), 5% (95% CI 0.6-19%), 3% (95% CI 0.1-14%), 14% (95% CI 5-29%) and 62% (95% CI 5-7%), respectively. Among survey participants, 76% (59-88%) had moderate to high CVD risk according to the 2013 American College of Sports Medicine guidelines. Eighty-two per cent of participants did not meet the National Fire Protection Association's required cardiorespiratory fitness standard of 12 metabolic equivalents. CONCLUSIONS: A high proportion of female firefighters in this study were at moderate to high risk of CVD. These findings suggest that they would benefit from healthy lifestyle initiatives.

Daily physical education in primary school and physical activity in midlife: the Trois-Rivières study.

AIM: Although a commonly stated purpose of physical education (PE) classes is to foster life-long participation in physicalactivity (PA), few longitudinal studies have assessed the impact of childhood PE interventions on PA as an adult. The Trois-Rivières Growth and Development Study provided a unique opportunity to address this question. METHODS: In 2008, 86 participants in the original 1970-1977 Trois-Rivières Study (44 women and 42 men aged 44.0 ± 1.2 years) completed a questionnaire examining their current PA level and different correlates of PA (i.e. individual's intention to engage in PA, perceived enjoyment, usefulness and ease in engaging in PA, perceived social support and social norms). Participants had initially been assigned to either an experimental program (5 h/week of specialist-taught PE) or a control group (40 min/week of home-room teacher-taught PE) from grades 1 to 6. RESULTS: There were no current differences between the experimental and control groups neither in the frequency, duration nor volume of PA undertaken at the current follow-up. Furthermore, no differences between groups were found for any of the PA correlates examined. CONCLUSION: Providing daily PE throughout primary school seems insufficient to ensure that individuals will remain active in midlife. The development of a life-course approach to PA promotion is thus warranted.

Daily quality physical education in childhood and adult bone density.

AIM: Previous studies, mainly of self-selected athletes, have suggested that childhood activities can have a prolonged influence on bone mineral density. This investigation explored whether experimentally assigned daily quality physical education (PE) during childhood influenced bone density at an age of 42.8±1.5 years. METHODS: Participants from the Trois-Rivières Longitudinal Study were divided into 4 groups: the first 2 groups (19 women and 21 men) had received 5 h/week of specialist-taught PE in primary school in 1970-1977, whereas the third and fourth groups (10 women and 10 men) had followed the standard PE programme of 40 min/week. RESULTS: Bone densities, measured by dual X-ray absorptiometry (lumbar vertebrae and femoral neck), did not differ significantly between experimental and control subjects. CONCLUSION: This result may reflect a normal or even a faster decrease of bone mineral density in experimental subjects over the 30 years since completion of the program, or an intervention that was designed to enhance cardiorespiratory and muscular fitness rather than bone health.

Factors influencing the adoption of a health promoting school approach in the province of Quebec, Canada.

This study examined a prediction model that integrated three categories of predictors likely to influence adoption of the Quebec Healthy Schools (HS) approach, i.e. attributes of the approach, individual and contextual characteristics. HS receptivity was considered as a potential mediator. For this study, 141 respondents representing 96 schools participated in a postal survey. We used bivariate logistic regression to assess factors associated with HS adoption and Baron and Kenny's method to test the mediation effect of HS receptivity. Four predictors related to school organizational characteristics had more weight in influencing the adoption of HS: the 'presence of leaders within schools', 'perceived school contextual barriers', 'school investment in healthy lifestyles' and 'beliefs in collective efficacy'. The influence of the latter two predictors was not direct but mediated by HS receptivity. Our findings showed that standard attributes generally considered as predictors of the adoption of an innovation are not the strongest determinants to explain HS adoption in the present context. The results shed light on the crucial role of organizational context in the adoption of this type of approach.

Binding properties of glutamate receptors in streptozotocin-induced diabetes in rats.

The biochemical mechanisms by which diabetes modulates cognitive function are not well established. Here, we determined the effects of streptozotocin (STZ) administration on the binding properties of alpha-amino-3-hydroxy-5-methylisoxazolepropionic acid (AMPA) and N-methyl-D-aspartate (NMDA) subtypes of glutamate receptors in rats, using quantitative autoradiographic analysis of (3)H-AMPA and [(3)H]glutamate binding on brain tissue sections. The STZ injection (70 mg/kg intraperitoneally) produced a reduction of (3)H-AMPA binding in various brain regions, an effect that is due to a decrease in receptor affinity. The STZ-induced reduction of (3)H-AMPA binding varied in different brain structures, being more pronounced in the striatum, cerebral cortex, and hippocampus and almost absent in the cerebellum. Western blots performed on hippocampal membranes revealed that the decrease in (3)H-AMPA binding is possibly associated with changes in immunologic properties for one glutamate receptor subunit (GluR1). Finally, the effect of STZ-induced diabetes appeared to be specific to the AMPA subtype of glutamate receptors, as the same treatment did not modify [(3)H]glutamate binding to NMDA receptors. These changes in AMPA receptor properties may have important implications for understanding the biochemical mechanisms underlying cognitive impairment in diabetes.

Effects of dominant somatotype on aerobic capacity trainability.

PURPOSE: This study examined the association between dominant somatotype and the effect on aerobic capacity variables of individualised aerobic interval training. METHODS: Forty one white North African subjects (age 21.4+/-1.3 years; Vo2max = 52.8+/-5.7 ml kg(-1) min(-1)) performed three exercise tests 1 week apart (i) an incremental test on a cycle ergometer to determine Vo2max and Vo2 at the second ventilatory threshold (VT2); (ii) a VAM-EVAL track test to determine maximal aerobic speed (vVo2max); and (iii) an exhaustive constant velocity test to determine time limit performed at 100% vVo2max (tlim100). Subjects were divided into four somatometric groups: endomorphs-mesomorphs (Endo-meso; n = 9), mesomorphs (Meso; n = 11), mesomorphs-ectomorphs (Meso-ecto; n = 12), and ectomorphs (Ecto; n = 9). Subjects followed a 12 week training program (two sessions/week). Each endurance training session consisted of the maximal number of successive fractions for each subject. Each fraction consisted of one period of exercise at 100% of vVo2max and one of active recovery at 60% of vVo2max. The duration of each period was equal to half the individual tlim100 duration (153.6+/-39.7 s). After the training program, all subjects were re-evaluated for comparison with pre-test results. RESULTS: Pre- and post-training data were grouped by dominant somatotype. Two way ANOVA revealed significant somatotype-aerobic training interaction effects (p<0.001) for improvements in vVo2max, Vo2max expressed classically and according to allometric scaling, and Vo2 at VT2. There were significant differences among groups post-training: the Meso-ecto and the Meso groups showed the greatest improvements in aerobic capacity. CONCLUSION: The significant somatotype-aerobic training interaction suggests different trainability with intermittent and individualised aerobic training according to somatotype.

Greater physical fitness is associated with better air ventilation efficiency in firefighters.

Firefighting is a hazardous task associated with a heavy workload where task duration may be limited by air cylinder capacity. Increased fitness may lead to better air ventilation efficiency and task duration at a given heavy work intensity. This study compared performance, air ventilation and skeletal muscle oxygen extraction during a maximal graded walking test (GWT), a 10 METS (metabolic equivalent) treadmill test (T10) and a simulated work circuit (SWC). Participants (n = 13) who performed the SWC in a shorter time had significantly lower air cylinder ventilation values on the T10 (r = -0.495), better peak oxygen consumption (r = -0.924) during the GWT and significantly greater skeletal muscle oxygen extraction during the SWC (HbDiff, r = 0.768). These results demonstrate that the fastest participants on the SWC had better air ventilation efficiency that could prolong interventions in difficult situations requiring air cylinder use.

Plasma catecholamines in the aorta and the phrenicoabdominal vein in exercising dogs.

Plasma epinephrine and norepinephrine concentrations were measured in the aorta and phrenicoabdominal vein in five dogs at rest and during short-duration mild- and moderate-intensity exercise and during prolonged mild-intensity exercise. Plasma epinephrine and norepinephrine concentrations increased with exercise in both the aorta and the phrenicoabdominal vein. Plasma epinephrine concentration was much higher in the phrenicoabdominal vein than in the aorta (24-43 times). Plasma epinephrine concentrations in the aorta and phrenicoabdominal vein were significantly correlated (r = 0.88). This confirms that peripheral epinephrine concentration is a reliable index of the activity of the adrenal medulla during exercise. The epinephrine-to-norepinephrine ratio in the phrenicoabdominal vein was stable (4:1) throughout the experimental protocol, suggesting that the proportion of the two amines released by the adrenal medulla did not vary through this range of adrenal activity in dogs.

Lack of antilipolytic effect of lactate in subcutaneous abdominal adipose tissue during exercise.

The purpose of our study was to evaluate the potential inhibition of adipose tissue mobilization by lactate. Eight male subjects (age, 26. 25 +/- 1.75 yr) in good physical condition (maximal oxygen uptake, 59.87 +/- 2.77 ml. kg-1. min-1; %body fat, 10.15 +/- 0.89%) participated in this study. For each subject, two microdialysis probes were inserted into abdominal subcutaneous tissue. Lactate (16 mM) was perfused via one of the probes while physiological saline only was perfused via the other, both at a flow rate of 2.5 microl/min. In both probes, ethanol was also perfused for adipose tissue blood flow estimation. Dialysates were collected every 10 min during rest (30 min), exercise at 50% maximal oxygen consumption (120 min), and recovery (30 min) for the measurement of glycerol concentration. During exercise, glycerol increased significantly in both probes. However, no differences in glycerol level and ethanol extraction were observed between the lactate and control probes. These findings suggest that lactate does not impair subcutaneous abdominal adipose tissue mobilization during exercise.

Effect of carbohydrate ingestion on adipose tissue lipolysis during long-lasting exercise in trained men.

To study whether sucrose administration acts on lipid mobilization during prolonged exercise, we used subcutaneous abdominal adipose tissue microdialysis in eight well-trained subjects submitted at random to two 100-min exercises (50% maximal aerobic power) on separate days. After 50 min of exercise, the subjects ingested either a sucrose solution (0.75 g/kg body wt) or water. By using a microdialysis probe, dialysate was obtained every 10 min from the subjects at rest, during exercise, and during a 30-min recovery period. During exercise without sucrose, plasma and dialysate glycerol increased significantly. With sucrose, the response was significantly lower for dialysate glycerol (P < 0.05). Plasma free fatty acid level was lower after sucrose than after water ingestion (P < 0.05). With water ingestion, plasma catecholamines increased significantly, whereas insulin fell (P < 0.05). With sucrose ingestion, the epinephrine response was blunted, whereas the insulin level was significantly increased. In conclusion, the use of adipose tissue microdialysis directly supports a lower lipid mobilization during exercise when sucrose is supplied, which confirms that the availability of carbohydrate influences lipid mobilization.

Impaired modulation of AMPA receptors by calcium-dependent processes in streptozotocin-induced diabetic rats.

The mechanisms by which diabetes impairs cognitive function are not well-established. In the present study, we determined the electrophysiological and biochemical nature of disturbances in the mechanism of long-term potentiation (LTP) in diabetic rats. As previously reported, the administration of streptozotocin (STZ) was found to reduce the magnitude of LTP in the CA1 region of the hippocampus, while the same treatment did not interact with the capacity of the hippocampus to generate long-term depression induced by low-frequency stimulation. In addition, STZ treatment did not modify the component of excitatory postsynaptic potentials mediated by activation of the N-methyl-D-aspartate (NMDA) subtype of glutamate receptors, suggesting that NMDA receptor function remained intact in STZ-treated slices. At the biochemical level, the capacity of calcium to increase [3H](RS)-alpha-amino-3-hydroxy-5-methylisoxazole propionic acid (3H-AMPA) binding to glutamate/AMPA receptors in rat brain tissue sections was markedly affected in most regions of the hippocampus of STZ-treated rats. Moreover, changes in 3H-AMPA binding properties elicited by both exogenous phospholipase A2 and melittin, a potent activator of endogenous phospholipases, were also altered in synaptoneurosomes from diabetic rats. Taken together, the present data suggest that the loss of LTP maintenance in STZ-treated rats is more likely the result of disruption of calcium-dependent processes that are suspected to modulate postsynaptic AMPA receptors during synaptic potentiation. Understanding the biochemical factors participating in the impairment of AMPA receptor modulation might provide important clues revealing the very basis of memory deficits in diabetes.

Effects of potassium-aspartate salt administration on glycogen use in the rat during a swimming stress.

The ergogenic effect of aspartate salts on performance during prolonged exercise is still controversial. Potential mechanisms of the suggested ergogenic effect of aspartate on exercise performance are a sparing of muscle glycogen stores or its faster resynthesis during exercise. The purpose of this study was to determine whether aspartate causes a sparing of muscle glycogen during exercise. Six groups of rats were studied: one group received a single injection of aspartate (1 g.kg-1, IP) and was then sacrificed at rest, a second group of aspartate-treated rats was sacrificed after a 60-min swim. The third and fourth groups were given an injection of physiological saline and then sacrificed respectively at rest and after a 60-min swim. The fifth and sixth groups were given an aspartate or a saline injection and then sacrificed after swimming to exhaustion. The exhaustion times after saline (178.9 +/- 38.2 min) and aspartate (174.4 +/- 45.2 min) were not significantly different. Results did not confirm an ergogenic effect of a single dose of aspartate on swimming endurance in the rat. Aspartate-treated rats had a significantly lower plasma FFA concentration after swimming to exhaustion when compared to control rats (respectively, 0.70 +/- 0.25 vs. 1.16 +/- 0.45 mM). Also, the results of the present study do not support the hypothesis of a sparing of muscle or liver glycogen with aspartate, because a similar content of glycogen remained in the muscles and liver of control rats after a 60-min swim or after swimming to exhaustion.

Plasma galanin immunoreactivity in the rat after swimming.

The purpose of our experiment was to study plasma immunoreactive galanin in the rat after swimming. Four groups of rats were used. At rest, one group was studied after an intravenous injection of D-glucose while another group received a corresponding saline injection. The two remaining groups, treated respectively with glucose and saline, were investigated after a 30-min swimming session. After 30 min of rest in their respective cages, or after swimming, the animals were anesthetized for immediate blood sampling. The main observation was that plasma galanin was higher after swimming than after rest only in glucose-treated rats, in the vena cava (11.82 +/- 2.90 vs. 5.05 +/- 1.65 pM) and the portal vein (15.75 +/- 3.74 vs. 6.58 +/- 1.75 pM). Both saline- and glucose-treated groups had a significant increase of plasma norepinephrine from rest to swimming in the vena cava. A decrease of plasma insulin was observed in the portal vein of exercised glucose-treated rats, while plasma glucose was higher in the portal vein of this group. In conclusion, after swimming, plasma galanin level was increased only in glucose-treated rats. A significant correlation was also observed between plasma galanin and glucose (r = 0.69, p < 0.01), suggesting that the presence of glucose is necessary to induce galanin liberation during exercise.

Capsaicin-sensitive nerves and endurance exercise in the rat.

The purpose of our study was to clarify the role of capsaicin-sensitive nerves in the control of plasma catecholamine and glucose concentrations during exercise. In vehicle-treated rats, plasma epinephrine (E) and norepinephrine (NE) levels were significantly higher in animals exercised to exhaustion than in the group sacrificed at rest. However, it was not the case for the neonatally capsaicin-treated animals. The epinephrine and norepinephrine levels were not significantly higher in the capsaicinized animals exercised to exhaustion than in those studied at rest. As a result, plasma epinephrine and norepinephrine levels were higher in control than in capsaicinized exhausted animals. Impairment of capsaicin-sensitive nerves by the neonatal capsaicin treatment prevented the exercise-induced increase of catecholamine output despite a significant decrease in plasma glucose levels and a lower liver glycogen content at rest. We suggest that this impairment of catecholamine output during exercise was caused by depletion of substance P in C-fibers directed to the adrenal medulla. This is supported by the observation of a lower plasma epinephrine level in capsaicin-treated rats. We conclude that C-fibers are therefore involved in the control of catecholamine secretion by the adrenal medulla during exercise to exhaustion. However, such an impairment of catecholamine output was not associated with a further decrease in plasma glucose levels or a shorter time-to-exhaustion. This also suggests that a partial dysfunction of the adrenal medulla is not sufficient to alter exercise endurance and plasma glucose levels.

PNMT inhibition decreases exercise performance in the rat.

The purpose of this investigation was to examine the effect of phenylethanolamine N-methyltransferase (PNMT) inhibition on the regulation of peripheral metabolic and hormonal responses during treadmill exercise in the rat. Changes in plasma catecholamine (epinephrine, norepinephrine, and dopamine), glucagon and glucose, and the glycogen content of the liver and two skeletal muscles were studied in four groups of rats. Two groups of rats were studied at rest: one group had been treated with LY134046, an inhibitor of PNMT, and the second group was treated with physiological saline. A third group treated with LY134046 was studied after treadmill exercise (28 m.min-1 and 8% slope). In this group of rats, exhaustion came after 37.5 +/- 7.9 minutes of exercise. In order to make appropriate comparisons, a fourth group of rats treated with physiological saline was exercised for 37.5 min. Running endurance during the treadmill exercise was thus reduced in LY134046-treated rats. Plasma epinephrine and glucagon concentrations and other metabolic (plasma glucose and gastrocnemius lateralis and superficial vastus lateralis muscles and liver glycogen contents) responses were similar between LY134046- and saline-treated rats at rest and after exercise. These results suggest that PNMT inhibition in epinephrine brain neurons might be the principal factor involved in the LY134046-induced reduction of exercise endurance.

Daily primary school physical education: effects on physical activity during adult life.

PURPOSE: The purpose of this investigation was to study the influence of a daily primary school physical education program on physical activity (PA) level, attitudes toward physical activity, and perceptions of barriers to physical activity during adulthood. METHODS: We compared two groups: 1) an experimental group of men and women (N = 147) who had received five physical education sessions per week throughout their 6 yr of primary school education in the early 1970s; and 2) a control group, drawn from the data bank of the Québec Health Survey, and matched for age, gender, and socioeconomic profile (N = 720). Experimental and control subjects filled out an identical questionnaire about their current physical activity level, their attitudes toward PA, and their perceptions of barriers to PA. The control group was stratified to obtain the same sociodemographic profile as the experimental group. RESULTS: Our principal results were: 1) a frequency distribution that showed a higher rate of physical activity in experimental women than in control women; 2) similar intentions to exercise and attitudes toward exercise in the experimental and control groups, with no differences in opportunities for exercising or in the support received from their family and friends; and 3) a lower prevalence of regular smokers in experimental men than in control men. There were also some differences in the types and frequency of physical activities selected between experimental and control subjects. CONCLUSION: Our results strongly suggest that daily physical education at the primary school level has had a significant long-term positive effect on the exercise habits on women, despite similar perceived barriers, attitudes, and intention to exercise in the two groups. The program has also had a significant health effect in men, substantially reducing the risk of becoming a regular smoker. Because the program was not specifically designed to promote health, we hypothesize that a health-oriented physical education program could have an even stronger effect.

Modelling and gait evaluation of asymmetrical-keel foot prosthesis.

The paper documents a new concept in prosthetic foot design. It is based on the capacity of a flexible keel to allow a greater medio-lateral function than previously available. The heel has a complex curvature consisting of a medially concave shape that joins the mid-foot. There a hump acting as a leaf-spring ends at the metatarsal break, with an inwardly curved toe extremity. These curvatures contribute to increased medio-lateral control at heel-strike and propulsion for weight transfer and push-off. Results from finite-element modelling indicate that the asymmetrically shaped keel is at least twice as active in storing energy compared with a completely symmetrical one. A preliminary gait study is carried out for a 24-year-old below-knee amputee fitted with the new design, the SPACE foot and a dynamic elastic response foot with a symmetrical keel. With the SPACE foot, there is a 14% increase in walking speed combined with a reduction in the phasic asymmetries. The absolute difference between the initial and terminal double support is 1.4% for the asymmetrical keel design compared with 4.4% for the symmetrical keel foot prosthesis. The peak ankle power generation burst indicates that the SPACE foot behaves as a dynamic elastic response foot.

Eye Injuries in Sports: Results of a Five-Year Study.

In brief: From 1982 to 1986, Quebec ophthalmologists reported 869 sports-related eye injuries. Hyphema was the most common injury, with a frequency of 33%. Most injuries occurred in ice hockey, followed by racket sports (32% and 28%, respectively); most of the injured players were not wearing eye protection. The authors suggest that wearing eye protection should be mandatory in some sports and encouraged in many others.

Estimation of energy expenditure in a work environment: comparison of accelerometry and oxygen consumption/heart rate regression.

The aim of this study was to compare estimation of energy expenditure (EE) in working environments, either from accelerometry or from an individual oxygen consumption/heart rate (VO(2)/HR) regression curve. The study participants were 46 volunteer workers aged 27+/-6 years old. A significant correlation between EE predicted by the VO(2)/HR curve and the accelerometer was observed (r=0.78, p <0.01). However, more disparities were observed between the two methods when the mean job intensity was not within 16% and 23% higher than resting HR. The accelerometer overestimated by a mean of 34.4% the prediction by VO(2)/HR regression if the intensity of the task was lower than a total of 1000 kcal/shift and underestimated the prediction by a mean of -24.9% if EE estimation of the work shift was higher than a total of 1500 kcal/shift. Despite a high correlation between both methods in the whole group, EE evaluated by accelerometry does not correspond to EE predicted by the VO(2)/HR regression curves when evaluated individually.