ABSTRACT
It is well known that decreased physical performance induces the decreased activity of daily living and increment of mortality rate in elderly subjects. On the other hand, a prolonged heart rate corrected-QT (QTc) interval is associated with an increased risk of cardiac sudden death and cardiac autonomic dysfunction. We investigated the associations between physical performance and QTc interval in elderly subjects. The subjects included 605 elderly persons (274 men and 331 women, age; 71.2±4.7 years) without a history of cardiovascular disease and taking cardioactive drugs. Resting 12-leads electrocardiography was measured after more than 5 minutes of rest. The QTc interval was calculated according to Bazett’s formula. The physical fitness test was performed to determine the physical performance (muscle strength, balance and walking abilities). The subjects were divided into four categories, which were defined as equally quantile distributions of QTc interval. The physical performance levels were significantly lower in the longest QTc interval group compared to the shortest QTc interval group in both men and women (p<0.05, respectively). Moreover, after adjusting for the age, the physical performance levels were significantly lower in the longest QTc interval group compared to the shortest QTc interval group, especially, this relationship was observed in late-stage elderly group (p<0.05, respectively). These results suggest that decreased physical performance levels were also associated with prolonged QTc interval in elderly subjects.
ABSTRACT
Prescribed exercise regimens based on the target heart rate (THR) and the target work rate (TWR) on a cycle ergometer at the intensity of the lactate threshold (LT) were evaluated before, and after 6 and 12 weeks of exercise therapy in obese subjects with (OBHT, n=38) and without hypertension (OB, n=55) matching for age, sex, BMI, body composition, as well as the blood glucose, cholesterol and triglyceride level. THR was 97.8±9.2 in OBHT and 98.3±10.7 in OB without group differences. The resting HR was higher in OBHT than in OB (76.3 vs. 72.1). Both the relative THR (%HR reserve) and the relative TWR (%Body weight) were lower in OBHT than in OB. During the training period, the VO<sub>2</sub>max, THR and TWR increased while body fat decreased significantly in both groups. The resting BP and HR decreased, and the %HRR increased significantly in OBHT. In conclusion, the lower THR and TWR are therefore recommended when initially prescribing an exercise regimen without an exercise stress test for obese individuals, particularly for the obese subjects with HT based on the exercise intensity at LT. Thereafter, careful modifications in the prescribed exercise regimen will be needed according to improvements in the fitness level and in coronary risk factors.
ABSTRACT
Heart rate (HR) corresponding to lactate threshold (LT) was evaluated in patients with multiple risk factors and applied to determine the target HR by Karvonen's formula calculated from the predicted HR max. The subjects were 52 outpatients (33 men and 19 women) aged from 23 to 70 years old (mean 46.9) with more than 2 risk factors including obesity, hypertension, diabetes mellitus, impaired glucose tolerance, dyslipidemia, hyperuricemia, and hyperinsulinemia. A multistage graded test of submaximal exercise on electric bicycle ergometer was performed for each subject before starting exercise therapy. The workload was increased every 4 minutes, and heart rate, blood pressure, and blood lactate concentration were measured during the last 1 minute of each stage. The LTHR ranged from 80 to 120 beats/min (mean 101±10) and Karvonen's coefficients ranged from 0.08 to 0.40 (mean 0.22±0.08) . Because of these differences and variance, it is suggested that LTHR should be measured directly or about 20% HR reserve should be prescribed at least when starting exercise therapy for these cases.