Monitoring changes in oxygen extraction by working muscles during an incremental cyclergometer exercise in chronic heart failure (CHF) patients, before and after a 16 week period of resistance training, by near infrared spectroscopy (NIRS). Subjects: 12 CHF patients (age 45-75, all males, NYHA class II) carrying an implantable defibrillator. Incremental test to exhaustion with steps of 10W*min^-1 before and after a 4 month resistance training. In comparison with pre training, post training NIRS recordings showed a doubling (P<0.05) in oxygen extraction at workloads 40 W to 70 W (all subjects). At the peak load of 97±18 before and 108±35W after training, extraction was 45.7±29.8% and 65.3±35.22% (P<0.05), respectively.

Resistance training, which is seldom prescribed, and often even forbidden, to CHF patients, is expected to produce skeletal muscle hypertrophy or to prevent atrophy (a common, severe, evolution of chronic heart failure), but ought not to interfere with oxygen utilization. The present results, to the contrary, demonstrate that resistance trained muscles in CHF patients significantly improve their oxygen utilization, as attested by enhanced extraction during similar absolute and relative workloads. This may be attributed either to build up of mitochondrial oxidative enzymes, or to enhanced capillarity, or both, although the precise mechanism cannot be disclosed in our experimental setup.