Flexibility & Stretching Zone!

Functional Flexibility

Lower Extremity Stretching in All Three Planes of Motion


by Mary Repking, PT, CSCS

Knowledge of biomechanics demonstrates that stretching a muscle in a single plane does not achieve full lengthening of that muscle. Additionally, most athletic activity and activities of daily living occur with one or two feet on the ground. The importance of the interaction of the joints in all three planes, the resultant lengthening of the musculature, and greater range of motion of the joints which occurs in the weight bearing positions enforces the need to perform stretching in both a weight bearing position and in all three planes of motion.

Past attempts at stretching devices have typically offered single plane stretching in a non-weight bearing position. Devices that are weight bearing typically stretch only in the sagittal plane (front to back motion).

TRI-STRETCH® allows for biomechanically correct lengthening of the muscles of the lower extremity in all three planes while in a functional, weight bearing position…replicating the exact joint movement and  muscle stretch of the running form.

Here's how….

The biomechanics of function consist of a complex combination of systems within and outside our bodies (ie gravity) that are linked and react with each other. An understanding of the interaction of all joints in all three planes of movement with gravity and ground reaction forces is needed to perform optimum stretching of the musculature. The three planes of movement include the frontal plane (side to side motion), the sagittal plane(frontward to backward motion) and the transverse plane(rotational motion).

In gait, running and other weight bearing activities, understanding begins with the foot. In normal gait when taking a step, the heel hits the ground and the calcaneus strikes on its lateral aspect. The calcaneus then everts (frontal plane motion) secondary to gravity and ground reaction forces. Along with the eversion, the subtalar joint abducts(transverse plane motion). Dorsiflexion then occurs by the lower leg moving across the planted foot (sagittal plane motion). These combined motions describe pronation movement in all three planes at any joint to load the muscles. Pronation is also occurring at the midtarsal joint. This is described as inversion, abduction and dorsiflexion of the forefoot in relation to the rearfoot.  Pronation at the rearfoot loads or lengthens the posterior tibialis muscles and the calf muscles (including the Achilles tendon). Pronation at the forefoot lengthens the peroneus longus.

Calcaneal eversion, and the resultant pronation at the foot, causes pronation to occur along the entire lower extremity kinetic chain. Higher up the chain, the knee flexes (sagittal plane), abducts(frontal plane) and internally rotates(transverse plane). As a result, the hip follows by flexing (sagittal plane), adducting (frontal plane) and internally rotating (transverse plane). This pronation at the hip lengthens or loads the hip extensors including the hamstrings, the abductors, the iliotibial band and the external rotators.

Stretching of the muscles is a commonly accepted practice for proper warm-up/cool-down in athletic activity. Research and clinical practice re-enforces that stretching reduces the potential for injury. All joints need to have their full range of motion in all three planes of movement to allow the body to move without deviation from normal biomechanics. When a joint is restricted in its motion (secondary to a shortened soft tissue), any force that drives the joint into motion it does not have will result in breakdown or acute injury to that joint or in structures somewhere above or below it within the kinetic chain. Maintaining tri-planar flexibility is therefore important for the athlete as well as the person attempting to stay fit.

For more information on functional flexibility, check out TRI-STRETCH® which includes an instructional DVD.