I found working out in the gym a couple of week where you perfrom targeting exercises for back/shoulders/chest and legs works well but don't miss out on your core - it really helps with control. Leg raises, cycling and crunches will help strengthen the core but russian twists are the best!
Russian Twists
1. Lie on the floor (lock your feet under a stationary object and raise your shoulders a
couple inches off the floor to aid movement).
2. Place your palms together, straight up in the air. Your arms should be stretched completely out at a point just below your chin. You may hold a weight in your hands for greater resistence. Typically people use 5-25 pound plates.
3. Rotate your shoulders to the right side. Your hips should stay rigid and your palms should move a complete 90 degrees.
4. Repeat this movement to the opposite side.
5. Continue until failure.
Also - for your lower back - try the 'Good Morning'
1. Hold a barbell with an overhand grip so that it rests on your upper back and not on your neck. Set your feet a shoulder-width apart and knees slightly bent while keeping your back straight. Focus your eyes forward.
2. Gradually bend forward using your hips to lower your chest while maintaining the natural arch in your lower back. Keep your head up and maintain about the same angle of your knees.
3. Lift your upper body back into starting position.
And for your legs - squats work well.
1. From a rack with barbell upper chest height, position bar high on back of shoulders and grasp barbell to sides. Dismount bar from rack and stand with shoulder width stance.
Execution
2. Descend until thighs are just past parallel to floor. Extend knees and hips until legs are straight. Return and repeat.
Hope these help.