I have already written several articles pertaining to the use of a old bicycle inner tubes as a very effective exercise device. There are two major reason you should consider at least giving this a try. One, you are saving the environment by recycling your old inner tubes and transforming them into an exercise device that can be taken anywhere. Secondly, for some reason, old inner tubes are simply extremely effective in performing a multitude of exercises in both your warm-up and main set workouts. Not to mention that they are free, easily transportable, and easily replaceable if lost. I very rarely go on a trip without several different types of inner tubes (light road racing tubes, regular road bike tubes, and mountain bike tubes).
The most recent exercise I developed for use with either your road bike tubes or mountain bike tubes is what I called the lying hip flexor activation exercise. This requires that you lie flat on your back on the floor. Loop your inner tube around on itself so you have two loops in order to reduce the diameter of the tube in-half. Then lift both legs in the air with knees bent and at a 90 degree angle to the floor. Place the looped tube around your foot at about halfway up your arch. Then push one leg forward and the other back towards your chest activating your hip flexor. Focus on the pull back of the leg that is opposite the leg pushing forward.
This is a great movement to include after you have foam rolled, completed your stretching routine, and are ready to re-activate your muscles prior to your main workout. You will immediately feel the difference once you first stand-up from this movement and begin to walk. You will be amazed at the more fluid feeling you experience in your hip flexor and overall forward movement. I highly recommend this exercise to activate your muscles prior to any and all bike rides and runs. This will help prevent muscle tears and pulls if done on a regular basis and before all workouts and races.
Please refer to my other articles that include using old inner tubes for use in maintaining strength and general health for your rotator cuff, glutes, and chest. Use various inner tubes for varying resistance in your training. As always start out with the lighter more elastic tubes and build up gradually to the standard tubes. I like to use the mountain bike tubes for the lower body and not for the upper body since they provide too much resistance.