The benefits of exercise in the general population are well established [1, 2]. The current physical activity recommendation for adults aged between 18-65 years to promote and maintain health is to accumulate at least 30 minutes of moderately intense physical activity on at least five days of the week. Sedentary behaviour, such as time spent sitting is positively associated with coronary heart disease risk factors, obesity, and development of the metabolic syndrome [3, 4]. More recently, the link between sedentary behaviour and the development of certain cancer types has been reported.
Newer evidence indicates that increased physical activity after a cancer diagnosis may reduce the risk of cancer recurrence and mortality [5–7]. Cancer survivors are at risk of developing new primary tumours as well as secondary tumours and chronic diseases such as cardiovascular disease, osteoporosis, and diabetes . This increased risk across conditions may be genetic or treatment-related but may also reflect the fact that common life-style factors, including a sedentary lifestyle, increase the risk for more than one disease .
Physical activity is also advocated during and after the treatment for cancer. However, the adverse effects of treatment which frequently impact on physical functioning and quality of life, may persist even years after treatment [9–11], and must be taken into account. Many treatments for cancer are toxic, increasing the risk for a number of medical problems and late treatment effects such as neuropathy  and cardiovascular disease [12–14]. Cardiopulmonary capacity may also be compromised in cancer survivors because of side effects of therapy regimens such as weight gain and inactivity secondary to treatment. The reduction in cardiopulmonary capacity may lead to decreases in quality of life [15, 16]. A downward trajectory in aerobic fitness is generally observed, possibly caused by chemotherapy and associated side-effects such as anaemia, tachycardia, dehydration, and cardiac dysfunction [17, 18].
Other cancer survivors experience somatic symptoms which may also persist for years after treatment such as chronic fatigue [19, 20], weight gain , loss of muscle strength [21, 22] and difficulty sleeping . Physical and functional well-being are essential dimensions for overall quality of life , and poor physical functioning may explain some of the psychological distress experienced by cancer survivors [21, 22].
The rationale for physical activity interventions following cancer diagnosis includes minimizing biological processes associated with tumour growth , enhancing behavioural changes to try to minimise lifestyle risk factors for recurrence of cancer , and improving psychosocial factors during and after cancer . The main physiological outcomes of physical activity after cancer are improved fitness and physical functioning [27, 28], reduced fatigue , and modestly decreased weight and body fat .
Even though there is strong evidence for the benefits of physical activity aftercancer-treatment, the majority of cancer survivors do not meet public health guidelines for levels of physical activity necessary for health-related benefits [31–34]. Clearly, there is a need to promote physical activity, but the optimal intervention modality, intensity, training and duration are still unknown.
Many programmes in cancer rehabilitation are mainly based on psychotherapy or social support. Such therapies however do not usually deal with the physical problems encountered by many patients, such as fatigue, loss of functional capacity and weight gain . Many cancer rehabilitation programs and/or trials which include a physical rehabilitation are lengthy in duration, extremely intensive  and have tight eligibility criteria. They would be expensive to translate into general clinical practice or to apply to the general cancer survivor population.
We have therefore devised a RCT to evaluate the effectiveness and feasibility of an 8-week intervention to improve fitness and other secondary outcomes.