PHYSICAL RESPONSES TO DIFFERENT MODES OF INTERVAL EXERCISE IN PATIENTS WITH CHRONIC HEART-FAILURE - APPLICATION TO EXERCISE TRAINING

Method In exercise training with chronic heart failure patients, worki ng muscles should be stressed with high intensity stimuli without caus ing cardiac overstraining. This is possible using interval method exer cise. In this study, three interval exercise modes with different rati os of work/recovery phases (30/60 s, 15/60 s and 10/60 s) and differen t work rates were compared during cycle ergometer exercise in heart fa ilure patients. Work rate for the three interval modes was 50% (30/60 s), 70% (15/60 s) and 80% (10/60 s) of the maximum achieved during a s teep ramp test (increments of 25 w/10 s) corresponding to 71, 98 and 1 11 watts on average. Metabolic and cardiac responses to the three inte rval exercises were then examined including catecholamine levels and p erceived exertion. Parameters measured during interval exercise were c ompared with an intensity level of 75% peak VO2, determined during an ordinary ramp exercise test (increments of 12 . 5 W.min(-1)). Results ((x) over bar+/-SEM) (1) In all three interval modes, VO2, ventilation and lactate did not increase significantly during the course of exerc ise. Mean values during the last work phase were between 754+/-30 and 803+/-46 ml.min(-1) for VO2, between 26+/-3 and 28+/-11.min(-1) for ve ntilation and between 1 . 24+/-0 . 14 and 1 . 29+/-0 . 10 mmol.l(-1) f or lactate. (2) In mode 10/60 s, heart rate and systolic blood pressur e increased significantly (82+/-4-->85+/-4 beats.min(-1); 124+/-5-->13 4+/-5 mmHg; P<0 . 05 each), while in mode 15/60 s catecholamines incre ased significantly (norepinephrine 0 . 804+/-0 . 089-->1 . 135+/-0 . 0 94 nmol.l(-1); P<0 . 008; epinephrine 0 . 136+/-0 . 012-->0 . 193+/-0 . 019 nmol.l(-1); P<0 . 005). (3) In all three modes, rating of leg fa tigue and dyspnoea increased significantly during exercise but remaine d within the range of values considered 'very light to fairly light' o n the Borg scale. (4) Compared to an intensity level of 75% peak VO2, work rate during interval work phases was between 143 and 221%, while cardiac stress (rate-pressure product) was significantly lower (83-88% ). Conclusion All three interval modes resulted in physical response i n an acceptable range of values, and thus can be recommended.