Abstract: PP07-2

Muscle Strength Is a Better Predictor of Impaired Heart Rate Recovery Than BMI Among Firefighters

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Abstract


Impaired heart rate recovery (HRR) after exercise testing and obesity have been described as risk factors for cardiovascular diseases and overall mortality. The obesity paradox phenomenon has shown that physical fitness could be an important modifier effect when obesity is associated with higher cardiovascular and mortality risks. We aimed to evaluate the associations between obesity, physical fitness and heart rate recovery after exercise testing among firefighters. view more

Impaired heart rate recovery (HRR) after exercise testing and obesity have been described as risk factors for cardiovascular diseases and overall mortality. The obesity paradox phenomenon has shown that physical fitness could be an important modifier effect when obesity is associated with higher cardiovascular and mortality risks. We aimed to evaluate the associations between obesity, physical fitness and heart rate recovery after exercise testing among firefighters. We performed a cross sectional study within a large US fire department, applying a weighted sampling strategy, selecting randomly 100 participants from the eligible population; 75 at low cardiovascular risk and 225 at high risk. Inclusion criteria were: male > 18 yrs old with a recorded submaximal Bruce-treadmill test and no restrictions on duty. Impaired HRR was defined as HRR < 18 bpm at the 1st or < 42bpm at the 2nd min of the recovery period after exercise testing. Cardiorespiratory fitness (CRF) was estimated by the treadmill test and categorized as low and high. Muscle strength was evaluated by the push-ups test (PUT) and obesity was defined as BMI ≥ 30 kg/m2. 30 participants were excluded due to incomplete data. Crude associations were estimated by the odds ratio (OR-95%CI) and the multivariate analysis was assessed by binary logistic regression. Mann-Whitney test was used when applicable, at the 5% level of significance. Participants were 46.5 ± 8.3 years old, with BMI equal to 31.1 ± 4.7 km/m2. Prevalence estimates were 21.5% for HRR impairment and 55.4% for obesity. Median (interquartile range) of HRR at the 1st and 2nd min were 37 (27 - 46) and 54 (44 - 62) bpm, respectively. The odds of having impaired HRR were 2.74 (1.58 - 4.75) among obese as compared to non-obese; 3.11 (1.43 - 6.76) for those ≥40 years old vs the youngers and 2.71 (1.61 - 4.56) for those with lower CRF vs the fittest ones. Participants with normal HRR had better PUT than those with impaired HRR [25 (16 - 30) vs 16.5 (18 - 10), respectively)(p<0.001). After adjustments for age, push-ups, BMI and CRF as categories, only the number of push-ups remained significantly associated with impaired HRR, with OR=0.96 (0.94 - 0.99). Physical fitness appears to mediate age and obesity related HRR impairment. Each extra push-up was associated with 4% reduction in the odds of having reduced HRR profile. Our data support the need for considering physical fitness level in cardiovascular risk analyses among firefighters and to recommend muscle training as a potential cardiovascular protection factor.
Nothing to Disclose: LGGP, MNK, SM, SNK

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