As you begin your workout you may assume that stretching your muscles first will loosen them up for the work ahead. You may want to rethink that, many fitness experts now say that this type of stretching (static stretch) before exercise is not just counter-productive, but potentially damaging to the muscle.
A “cold” muscle is not as pliable as it may need to be to stretch it. Stretching causes the muscle fibers to extend to their limits. just as a piece of plastic is more flexible when heated; your muscles work in a similar way. A cold stretch may even cause the muscles to tighten rather than relax; exactly the opposite of what would be needed for a workout.
Stretching before you allow your muscles to acclimate themselves, blood flow being a key factor in acclamation, may cause your body to think it's at risk of being overstretched. It compensates by contracting the muscle and in turn becoming more tense. This will restrict your movement and increasing the potential for a pulled muscle. Working out in the morning can increase the chance of this happening due to the muscles being dormant for hours.
Instead of stretching, it’s suggested warming up with a light jog, depending on your fitness level the “light” is relative. But the take away is that you should work up a light sweat. That type of light movement increases the heart rate, blood flow to the muscles, and increases the body temperature. This will allow you to reach your full range of motion in a controlled manner.
Active stretches that work more muscles groups simultaneously, would be beneficial to add to your routine. The stretched muscle learns to extend while another group is working. These movements are common in yoga, which focuses on body alignment while stretching not just the flexibility of a muscle. These stretches involve the whole body and focus on stretching the muscle as well as the ligaments, tendons and joints associated with it.
Proper stretching should be a part of any triathlete's routine; it will help strengthen your body as well as help in mitigating if not preventing injury.