Trainer's Corner Week 5, Part IIIf: Swing

Swing (Phase 4): During this phase, the hamstring engages to provide knee flexion to help swing the limb forward ahead of your center of mass. This is because it requires more energy on your part to swing a limb with its weight at limb’s end than the weight concentrated near the joint (figure skater).


1. Knee flexion depends to a great extent on the flexibility of your quadriceps. This is because it will fight less against the contraction of your hamstrings. Now this all happens passively when we run, but this will be of important information to you in trying to maintain good running economy, especially when you start to feel fatigue settling in during your longer runs.

2. As the leg is swung forward, the active parts engaged are your abdomen, lower back, pelvis, and hips. Strength and flexibility in these areas will allow optimal stretch loading, thus setting you up to be a more economic runner. Core strength training is good for all the right reasons! Runners who lost rotational capacity in the low back due to age or general inflexibility loses virtually all input for the abdominal muscles and must come entirely from the hip flexor muscles. This means loss of power and more stress on the hip flexors. This is especially true during speed or hill training.

3. All in all, for the most part, tight hamstrings and weak abdominals will cripple the efforts for an unfortunate runner. Continue to strength train and cross train in order to supplement your running. If running is your only form of exercise, it will tend to work your low back at the expense of your abdominals, and repetitive sweeps of the hamstrings through a limited range of motion will further promote inflexibility. Tight hamstrings in running will force your body to compensate by tilting the lower pelvis forward, which will pull you into a slouching position.