Colorectal cancer is one of the most common cancers in Denmark, annually 4,200 men and women are diagnosed and approx. 2000 patients die of their colorectal cancer. As with other cancers, the risk of colorectal cancer increases with age, and the median age at diagnosis is 71 years. Improved treatment has increased the number of survivors with an expected 5-year survival rate of 50-60%. Characteristic of this group of patients is that at the time of diagnosis they often live with comorbidities and have limited leisure time physical activity.

There is evidence that rehabilitation in the form of physical exercise for cancer patients after their initial treatment has a positive effect on a number of physical and psychological parameter such as health-related quality of life, physical capacity and physical function, fatigue, anxiety and depression. However, the most frequently studied diagnosis group is women with breast cancer. Until now only few studies have evaluated the effects of physical activity among colorectal cancer patients receiving chemotherapy

The purpose of this study is: to examine the effect of two different training initiatives - 12 weeks progressive, high-intensity training versus low intensity exercise intervention - on physical, emotional and social habitus, in sedentary patients with colorectal cancer during adjuvant chemotherapy.

The hypothesis of the study are: 1. That both interventions will show a positive association between increased physical capacity (measured by aerobic capacity VO2-peak / peak oxygen uptake) and improved physical function, reduced fatigue and anxiety in the included sedentary colorectal cancer patients undergoing adjuvant chemotherapy.

Participants: Patients undergoing adjuvant chemotherapy for colorectal cancer who have self-reported physical activity level below the national recommended levels (less than 150 min/week of moderate leisure time physical activity, and exercises at least 20 minutes of strenuous physical activity twice a week).

Benefits and risks of participating: Possible benefits of the interventions: to reduce treatment related symptoms and side-effects, increase vitality and well-being and promote lifestyle changes among sedentary colorectal cancer patients receiving adjuvant chemotherapy. At participation in the interventions minor sports injuries may occur.

Inclusion Criteria:

• Diagnosed with colorectal cancer in adjuvant chemotherapy
• Age 18+ years
• WHO performance status of 0 or 1
• Undergone surgery at least 6 weeks ago
• Do not meet criteria for recommended physical activity level of 150 min / week of moderate leisure time physical activity, and exercises at least 20 minutes of strenuous physical activity twice a week.

Exclusion Criteria:

• Myocardial infarction within the past six months
• Symptomatic heart failure
• Known angina pectoris
• Contraindication for moderate to strenuous physical activity

Presently no plan to make IPD available to other researchers

Primary outcome (VO2 peak) Physiological tests assessors blinded