Use of the six-minute walk test in exercise prescription in male patients after coronary artery bypass surgery

Introduction
It is unclear whether it is possible to determine the training load on the basis of the 6-minute walk test (6-MWT) in patients after cardiac surgery with low tolerance of physical exercise. Aim: Use of the 6-MWT to determine an individual initial training load in walking training on a treadmill in the early phase of cardiac rehabilitation in men after coronary artery bypass graft (CABG) surgery.

Material and methods
Twenty-two men aged 54 to 74 years, up to 3 months after CABG surgery participated in walking training on a treadmill (12–15 sessions). Patients underwent the initial and final treadmill exercise stress test (TEST) and the 6-MWT. Based on 6-MWT results, the initial training load was prescribed. Before the 6-MWT and 3 minutes after its completion, lactate concentration was determined.

Results
The 6-MWT distance increased from 420 ±80 m to 519 ±61 m (p < 0.001), and the energy expenditure from 4.4 ±1.4 MET to 6.3 ±1.3 MET (p < 0.001). There was a positive correlation between 6-MWT distance and energy expenditure in the TEST before rehabilitation (r = 0.60, p = 0.005), and after rehabilitation (r = 0.75, p < 0.001). A negative correlation was found between the baseline 6-MWT distance and distance increment in the final 6-MWT (r = –0.66, p = 0.002). The 6-MWT did not induce hyperlactatemia.

Conclusions
The 6-MWT can be used in exercise intensity prescription, especially for determining the individual initial training load, load progression, as well as its correction during follow-up tests.