Brief Summary: The Exercising Together trial is a single-blind, parallel group, randomized controlled trial comparing 3 arms: Arm 1 (experimental): Exercising Together where couples perform partnered exercise in a supervised, group setting versus two comparator conditions where survivors and partners perform exercise routines separately in either a supervised group setting (Arm 2) or unsupervised at home (Arm 3). All three arms will train for a 6-month period and then be followed 6 months later. Data will be collected at baseline, 3, 6 and 12 months.

Detailed Description: PRIMARY OBJECTIVES: I. Determine the efficacy of Exercising Together on relationship quality (intimacy, communication and incongruence) in couples coping with prostate cancer (PC), breast cancer (BC), or colorectal cancer (CRC). II. Determine the efficacy of Exercising Together on the physical health (body composition, lipids, insulin resistance, blood pressure, inflammation, and physical function) and mental health (anxiety, depressive symptoms, fear of recurrence) of both the survivor and spouse/partner. III. Determine how long individual and couple-level benefits from Exercising Together last. EXPLORATORY OBJECTIVE: I. Identify the types of couples that benefit most from Exercising Together. OUTLINE: Study is a 3-group, 12-month (6 months of exercise training + 6-months follow-up) randomized trial. ARM I: Exercising Together Program: Couples perform partnered exercise over 1 hour, 2 days per week in a supervised, group setting. ARM II: Exercising Together Program: Couples perform partnered exercise over 1 hour, 2 days per week in a supervised, group setting ARM III: Survivors and partners undergo 2 training sessions over 1 hour with an exercise trainer and then perform exercise routines over 1 hour 2 days per week separately unsupervised at home or a facility following an instructional digital video disc (DVD). The basic training program for all three study arms is a functional strength training program. Participants will use free weights (weighted vest, dumbbells, elastic bands) while performing lower body (chair rises, squats, lunges, stepups) and upper body (1-arm row, bench press, push-ups, triceps extension, bicep curls, shoulder raise) resistance exercise. Volume of resistance exercise, determined by intensity (weight, tailored to each individual) and duration (number of repetitions and sets), is gradually increased from low weight and high repetitions to more weight and fewer repetitions over the training period.