The effects of exercise modality and intensity on energy expenditure and cardiorespiratory response in adults with obesity and treated obstructive sleep apnoea

Abstract

To inform recommendations for the exercise component of a healthy lifestyle intervention for adults with obesity and treated obstructive sleep apnoea (OSA), we investigated the total energy expenditure (EE) and cardiorespiratory response to weight-supported (cycling) and unsupported (walking) exercise. Individuals with treated OSA and a body mass index (BMI) > 30 kg/m² performed an incremental cardiopulmonary exercise test on a cycle ergometer and a treadmill to determine the peak oxygen uptake [Formula: see text]. Participants subsequently completed two endurance tests on each modality, matched at 80% and 60% of the highest [Formula: see text] determined by the incremental tests, to intolerance. The cardiorespiratory response was measured and total EE was estimated from the [Formula: see text]. Sixteen participants completed all six tests: mean [SD] age 57 [13] years and median [IQ range] BMI 33.3 [30.8-35.3] kg/m². Total EE during treadmill walking was greater than cycling at both high (158 [101] vs. 29 [15] kcal; p < 0.001) and moderate (178 [100] vs. 85 [59] kcal; p = 0.002) intensities, respectively, with similar cardiorespiratory responses and pattern of EE during rest, exercise and recovery. Contrary to current guidelines, walking might be the preferred training modality to achieve the combination of weight loss and increased cardiorespiratory fitness in adults with obesity and treated OSA.

Keywords: Energy expenditure; exercise; obesity; obstructive sleep apnoea; weight supported; weight unsupported.

Figure 1.

An example of how the power was calculated for the constant power tests from the incremental treadmill (triangles) tests and cycle (circles) tests. The $\stackrel{.}{\text{V}}{\text{O}}_2$ (solid reference line) was highest $\left(\stackrel{.}{\text{V}}{\text{O}}_{2\text{pk}}\right)$ on the treadmill test; 80% and 60% $\stackrel{.}{\text{V}}{\text{O}}_{2\text{pk}}$ were 2168 and 1626 mL minute⁻¹, respectively. Therefore, the power for the cycle endurance tests at 80% and 60% $\stackrel{.}{\text{V}}{\text{O}}_{2\text{pk}}$ were 134 W (circled 1) and 87 W (circled 2), respectively. The power for the endurance treadmill tests at 80% and 60% $\stackrel{.}{\text{V}}{\text{O}}_{2\text{pk}}$ was 102 W (circled 3) and 54 W (circled 4), respectively. The respective grade and speed for treadmill exercise was derived from the original protocol. In this case it was 9% grade at 4.2 km hour⁻¹ and 8% grade at 2.9 km hour⁻¹. $\stackrel{.}{\text{V}}{\text{O}}_{2\text{pk}}$: peak oxygen uptake; $\stackrel{.}{\text{V}}{\text{O}}_2$: oxygen uptake.

Figure 2.

A comparison of the exercise cardiorespiratory responses between incremental treadmill (triangles) and cycle (circles) ergometer tests in adults with obesity. $\stackrel{.}{\text{V}}{\text{O}}_2$: oxygen uptake; $\stackrel{.}{\text{V}}\text{E}$: ventilation, RER: respiratory exchange ratio.

Figure 3.

A comparison of the symptom responses between incremental treadmill (triangles) and cycle (circles) ergometer tests in adults with obesity.

Figure 4.

A comparison of the energy expenditure between weight-unsupported (treadmill) and -supported (cycling) exercise in adults with obesity. Treadmill (triangles) and cycling (circles) at high (a) and moderate (b) intensity exercise. The shaded area under the curve represents total energy expenditure, that is, work, above rest including recovery. Dashed line --- represents VO_2pk. $\stackrel{.}{\text{V}}{\text{O}}_{2\text{pk}}$: peak oxygen uptake.