Some people are loose, some people are tight and some people are in between. Those who are tight tend to be tight in the back of the body from head to heel. The hamstrings are deservedly the focus to a lot of attention but I have found that the calves don’t often get their due when it comes to being inflexible. The hamstrings and the calves basically shake hands as they cross paths on either side of the knee. The gastrocnemius muscle (half of the calf) has two heads that attach on either side of the femur bone. The three hamstring muscles have four heads between them that connect, two on each side, on both the tibia and the fibula.
The hamstrings bend (flex) the knee and straighten (extend) the hip, as in taking the thigh backward. When the trunk is fixed two of the hamstrings semitendinosus and semimembranosus extend the hip; when the knee is bent they also flex the knee and inwardly rotate the lower leg. The third of the hamstrings, biceps femoris, flexes the knee and outwardly rotates the lower leg when the knee is bent.
The calf muscles are responsible for plantarflexion—moving your foot and toes downward while lifting your heel up. This movement is key for walking, running and biking because it accomplishes the all-important push off through the inner foot.
The hamstrings and the calves are joined together by fascia, the connective tissue enveloping the entire body. Too many people focus on working and stretching the hamstrings without paying attention to the calves which are essentially connected to the hamstrings. And some calves are ridiulously tight.
The body needs to be figured out in balance so to open tight hamstrings we need to address all of the surrounding muscles, most specifically the calves and quadriceps (and we should add the glutes and tensor fasciae latae). This doesn’t include muscles of the trunk that are deeply affected by tight hamstrings so we will get to them at a later date.