Rudi Altig was a man before his time. In the 1960s, the German Tour de France bike racer known as the "yellow dwarf" was a yoga enthusiast. Before and after his arduous races he used yoga to relax his muscular body. Maybe he instinctively knew that yoga is the perfect foil for bicycling, a one-dimensional sport.
As a bicyclist travels through one plane, he or she repeatedly overtaxes some muscles and underutilizes others. Watch a cyclist coming toward you, and you can read the imbalances. Rocking side to side signals that one hip is compensating for the other's weakness or inflexibility. Hips are the core of movement for the cyclist. If the core is weak, then the upper body has to work harder, and this can lead to back strain.
Likewise, if a thigh or knee flares out from the bicycle seat due to weakness or chronic tightness, that side of the body is doing less work. The hips, thighs, knees, and ankles should all be on one track, pointing straight ahead. If these body parts are off track, cyclists run the risk of wearing down ligaments and tendons, and developing imbalanced muscle groups. And in cyclists, the quadriceps are often overdeveloped. To compensate for this, the hamstrings shorten, tighten, and thus weaken.
The posture a cyclist conforms to astride a bike also contributes to muscle tension and imbalance: A bicyclist's spine is in a constant state of flexion, hunched over the handlebars. In order to achieve overall flexibility and balanced muscle groups, a biker needs to incorporate balancing, counteracting movements, for example, backbends, which stretch and elongate oft-used hip flexors and quadriceps. A yoga practice can help restore balance, first by taking the alignment principles of yoga and transferring them to how you sit on your bike.
Thanks to Verity Bell http://www.kickstep.org/ for the photographs