Influence of exercise modality on agreement between gas exchange and heart rate variability thresholds

The main purpose of this study was to investigate the level of agreement between the gas exchange threshold (GET) and heart rate variability threshold (HRVT) during maximal cardiopulmonary exercise testing (CPET) using three different exercise modalities. A further aim was to establish whether there was a 1:1 relationship between the percentage heart rate reserve (%HRR) and percentage oxygen uptake reserve ( % V ˙ O 2  R ) at intensities corresponding to GET and HRVT. Sixteen apparently healthy men 17 to 28 years of age performed three maximal CPETs (cycling, walking, and running). Mean heart rate and V ˙ O 2 at GET and HRVT were 16 bpm (P<0.001) and 5.2 mL·kg-1·min-1 (P=0.001) higher in running than cycling, but no significant differences were observed between running and walking, or cycling and walking (P>0.05). There was a strong relationship between GET and HRVT, with R2 ranging from 0.69 to 0.90. A 1:1 relationship between %HRR and % V ˙ O 2  R was not observed at GET and HRVT. The %HRR was higher during cycling (GET mean difference=7%; HRVT mean difference=11%; both P<0.001), walking (GET mean difference=13%; HRVT mean difference=13%; both P<0.001), or running (GET mean difference=11%; HRVT mean difference=10%; both P<0.001). Therefore, using HRVT to prescribe aerobic exercise intensity appears to be valid. However, to assume a 1:1 relationship between %HRR and % V ˙ O 2  R at HRVT would probably result in overestimation of the energy expenditure during the bout of exercise.

Selection of Aerobic Exercise Intensity Using Heart Rate Reserve in Stroke Patients

OBJECTIVE: To determine the intensity of aerobic exercise in stroke patients using heart rate reserve (HRR) by comparing maximal oxygen consumption (VO2max) and VO2 at % HRR in maximal exercise test of treadmill, arm ergometer and bicycle ergometer. METHOD: Twenty nine stroke patients who could walk independently were included. Maximal exercise test using treadmill, arm ergometer and bicycle ergometer was performed. Heart rate, rating of perceived exertion, minute ventilation, oxygen consumption and respiratory exchange ratio were measured through respiratory gas analysis. When the standard criteria for maximal oxygen consumption (VO2max) was achieved, each test was terminated. We compared the measured VO2max with the VO2 at % heart rate reserve (HRR) and figured out the statistically significant % HRR point. RESULTS: Twenty-four (82.7%), twenty-four (82.7%) and twenty-five (86.2%) patients completed maximal exercise test using treadmill, arm ergometer and bicycle ergometer. Most patients who completed maximal exercise test satisfied the VO2max criteria with VO2 plateau at the end of the exercise test (41.3~48.2%) or RER > 1.0 (79.3~82.7%) or peak HR >age-predicted maximal heart rate (APMHR)-10 or peak HR > 70% {208-(0.7 x age)} when they took beta- blockers (6.8~13.7%). The differences between measured VO2max and VO2 above 60% HRR at treadmill test, 65% HRR at arm ergometer test, 65% HRR at bicycle ergometer test were not statistically significant (>0.05). CONCLUSION: Exercise above 60% HRR at treadmill test, 65% HRR at arm and bicycle ergometer test can be useful as aerobic exercise intensity in stroke patients.

APPLICATION OF HEART RATE AT LACTATE THRESHOLD TO KARVONEN'S FORMULA IN CASES OF MULTIPLE RISK FACTORS / 体力科学

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.