30 Jul Why Runners shouldnt wear flip-flops (or really, any athlete): Part 1
Most of us greet the summer with the beloved flip-flop. Becoming ever more popular, the flip-flop is a summertime staple. Rainbows, Reefs and Havanianas have become as trendy as the winter Ugg boot. But like the Ugg boot, the flip-flop has no ‘nutritional value’ to the runner, or the average person. There is no support and no structure.
Use of the flip-flop requires active muscle recruitment. Of course its good to actively use muscle, how else would we strengthen a muscle without using it? However, overuse is a different story.
The foot uses several muscles to hold a flip-flop on. Without these muscles working, the flop would literally flip off the foot completely. Mainly, we use the flexor muscles of the foot, the ones responsible for flexing the toes and ankle. Firing these muscles is what grips down on the flop, as seen when we ‘curl’ the toes. We use these muscles with every step, usually without realizing. Imagine, if you will, hanging from a pull-up bar. Eventually the wrist and hand muscles fatigue and we are forced to let go of the bar. The wrist and hand flexor muscles are contracting isometrically. The fingers are curled. There is no movement, but a constant contracted state. As we walk in flip-flops (and any other shoe without a back), we are forcing our foot and toe flexors into a constant isometric contraction. That state eventually becomes fatiguing.
The problem with fatigue, besides the obvious decline in performance that results, is the eventual tightening of the muscles. When a muscle or group of muscles is in a contracted state for long periods of time, it tends to grow tighter and tighter. A tight muscle cannot generate the most muscle force for a good contraction the way a normal muscle can. Thus performance decreases again.
These main muscles that are affected by the flip-flop happen to sit right behind the gastroc-soleus complex, that group you know of as the “calf” muscles. Underneath these muscles is where the muscles that flex the toe and ankle live. In reality, both the gastrocnemius-soleus complex and the rest of the ankle and toe flexors are effected by isometric contractions from a flip-flop, but because the latter group is significantly smaller in terms of length and girth, these muscles are extremely more likely to be negatively effected. By contrast, the calf is generally stronger and more resistant to fatigue, especially in a runner.
This entire group, the calf and the rest of the flexors, makes up the so-called posterior compartment. As most of you may have experienced, the posterior compartment is often the site of fatigue, tightness and subsequent injury. We know what its like to feel tight or tired or have less power or ‘push-off’ from the back of our legs. What you may not know is that most foot and ankle pain can also be blamed on this muscle group…everything from calf tears and strains, plantar fascitis to peroneal, posterior tibial or achilles tendonitis or ‘shin splints’, tibial stress syndrome and even stress fractures.