continuous and intermittent exercise in chronic heart failure patients

Continuous and Intermittent Exercise in Chronic Heart Failure Patients

Louisa Beale1, John Silberbauer2, Guy Lloyd2, Peter Watt1, Gary Brickley1

1. Chelsea School Research Centre, University of Brighton, Eastbourne, East Sussex BN20 7SR

2. Eastbourne District General Hospital, Eastbourne, East Sussex BN21 2UD

Introduction: Exercise for Chronic Heart Failure (CHF) patients

Continuous (below VT) (Meyer (T), 2005; Gordon & Scott, 1995, Demopoulos, 1997)

• Similar physiological demands in individuals• Moderate and maintainable intensity• Above VT increases LV wall stress and decreases LV function

Intermittent (Interval) (Meyer (K), 1996 & 1997, Wisløff et al, 2007)

• Greater stimulus to the periphery without over-taxing weakened heart• Allows challenge to heart’s pumping capacity• Greater improvements than after continuous training

BACR guidelines• 60-75/80 % predicted HRmax OR 40-60/70% HRR (Karvonen)• β-blockers: deduct 20-30 beats.min-1 from HRmax

• RPE 11-14

Aim

To compare exercise training intensities derived from cardiopulmonary exercise testing with current exercise prescription guidelines in CHF

• What are the acute responses to continuous (CON) and intermittent (INT) exercise at an intensity equivalent to 90% VT?

• Are current BACR guidelines likely to prescribe an exercise intensity at or below VT?

Methods

Patients: 10 (8 male 2 female) CHF (NYHA Class II-III)

Mean ± SDAge (yr): 75 ± 8Height (m): 1.74 ± 0.12Body mass (kg): 85 ± 16VO2 peak (ml.kg.min-1) : 15.4 ± 4.5 Medication: β-blockers n= 9, anti-arrhythmic

n = 3

Exercise Tests: Maximal exercise testcycle ergometerramp rate 10 W/min

Measurements: Resp. gas exch., HR, BP, RPE

.

2 x 20 min exercise bouts, 1 week apart, randomised, equal work doneContinuous: 90% VTIntermittent: work phase 110% RCP: 30s (x 13) recovery phase: 60s (x14)

REST

VT

RCP

VO2

PEAK

Exe

rcis

e In

tens

ity (W

)

Continuous Intermittent

45W

20

averageworkload

MODERATE

HEAVY

SEVERE

EXTREME

90W

25W

Time

EXERCISE DOMAIN1 2

Results

Comparison of exercise data at VT with average values during CON and INT

Mean ± SEM

VT CON INTAverage HR (beats.min-1) 80 ± 3 78 ± 3 77 ± 3

Average VO2 (ml.min-1) 810 ± 98 859 ± 86 869 ± 83

METS 3.0 ± 0.8 3.0 ± 0.7 3.1 ± 0.5

RPE 11.7 ± 0.9 12.1 ± 0.6

RPP* 101 ± 5 98 ± 5

* BP(mm.Hg-1) x HR (beats.min-1)/100

No significant differences were found

HR response to continuous and intermittent exercise in CHF patients and control subjects

HR during continuous exercise @ 90% VT relative to BACR guidelines

Peak HR and target HR ranges recorded during a maximal exercise test vs. predicted values

Recorded Predicted p value Maximum heart rate (beats. min-1) 105 ± 5 118 ± 4 * 0.02 Heart rate reserve (beats. min-1) 48 ± 5 61 ± 5 * 0.02 60% maximum heart rate (beats. min-1) 63 ± 3 71 ± 2 * 0.02 80% maximum heart rate (beats. min-1) 84 ± 4 94 ± 3 * 0.02 40% heart rate reserve (beats. min-1) 76 ± 3 81 ± 2 * ** 0.02 0.00 70% heart rate reserve (beats. min-1) 90 ± 4 99 ± 2 * ** 0.02 0.00

* p< 0.05: difference between recorded and predicted values

** p< 0.05: difference between % maximum or peak HR and %HRR methods

Recorded Predicted

HRmax (beats.min-1) 105 ± 5 118 ± 4 *HRR (beats.min-1) 48 ± 5 61 ± 5 *60% HRmax (beats.min-1) 63 ± 3 71 ± 2 *

40% HRR (beats.min-1) 76 ± 3 81 ± 2 * 80% HRmax (beats.min-1) 84 ± 4 94 ± 3 * **70% HRR (beats.min-1) 90 ± 4 99 ± 2 * **

*p< 0.05: difference between recorded and predicted values**p< 0.05: difference between % HRmax and %HRR methods

Practical Implications

• Exercise at or just below VT is well-tolerated, and intermittent is an alternative to continuous (next study will investigate continuous vs. intermittent at a higher intensity)

• Difficulty of accurate exercise prescription in CHF patients without CPET

• Don’t rely on % predicted HRmax to guide exercise intensity

• 40-70% HRR does not correspond with 60-80% HRmax

• HRR (Karvonen) method is likely to prescribe exercise at or above RCP, i.e. heavy exercise domain

Continuous and Intermittent Exercise in Chronic Heart Failure Patients

Louisa Beale1, John Silberbauer2, Guy Lloyd2, Peter Watt1, Gary Brickley1

1.Chelsea School Research Centre, University of Brighton, Eastbourne, BN20 7SR2. Eastbourne District General Hospital, Eastbourne BN21 2UD

ANY QUESTIONS?

Comparison of HR as % HRR, and VO2 as % VO2R at VT and during CON and INT

Identifying Ventilatory Threshold

Identifying RCP

Identifying VT and RCP

HR response to continuous and intermittent exercise in CHF patients and control subjects