Obesity is very common worldwide and breathing problems at night (obstructive sleep apnea, OSA) are common in obesity. Despite the best treatment, obesity and OSA are linked to early death from heart problems. They are also associated with lower levels of physical activity. Exercise strategies for weight loss, increasing physical activity and improving fitness are needed for obesity. In Obese individuals with OSA

1. The investigators will compare corridor walking tests compared to laboratory exercise tests. The null hypothesis is that the peak oxygen uptake achieved and the cardiopulmonary response during both the six-minute walk test and Incremental Shuttle Walk Test would not be different from that observed during an Incremental Treadmill Test.
2. The investigators will investigate whether cycling or walking uses more calories for the same intensity. We hypothesise that cycling (weight supported) will be endured for long.
3. The investigators will compare commonly used exercise tests with levels of daily physical activity.

The information from these three projects will help us set up the optimal exercise program for obese individuals.

Inclusion Criteria:

• Obstructive Sleep Apnea
• Obesity BMI>30
• Controlled on Continuous Positive Airway Pressure for three months

Exclusion Criteria:

• cardiac co-morbidity e.g ischaemic heart disease, chronic heart failure, valvular heart disease
• pulmonary co-morbidity
• neurological condition limiting the ability to perform walking or cycling
• orthopaedic condition limiting the ability to perform walking or cycling

Obstructive Sleep Apnea