Active Voice: Too Much Quadriceps, Too Little Calf

By Juha-Pekka Kulmala, Ph.D.

Viewpoints presented in SMB commentaries reflect opinions of the authors and do not necessarily reflect positions or policies of ACSM.

Juha-Pekka Kulmala, Ph.D., completed his doctoral degree in biomechanics through the University of Jyväskylä, Finland, and currently works as a clinical biomechanist in the Helsinki University Hospital, Finland. His research concentrates on walking and running biomechanics.

This commentary presents Dr. Kulmala's views on the topic related to a research article which he and colleagues authored. Their article appears in the November 2016 issue of Medicine & Science in Sports & Exercise® (MSSE).

We humans use our quadriceps and calf muscles to produce most of the support needed for locomotion. However, little is known about how the upper functional limits of these key muscle groups contribute to performance in walking or running activities. This knowledge would be of crucial importance in the broad context of human locomotion, because the muscles operating nearest to their maximum limits are the "weak link" and, therefore, are the most efficient targets for exercise interventions aimed at improving walking or running performance.

Our proof-of-concept study, as reported in the November 2016 issue of MSSE, offers — for the first time — a reasonable approximation of the quadriceps and calf muscle efforts for level walking and running. In this research, we determined operating efforts by relating muscle outputs developed across locomotor tasks to maximum outputs of the same muscle groups obtained from a reference hopping test that permitted natural elastic leg behavior.

We found that, during walking, the calf muscle operated at almost two times greater relative level compared with the quadriceps muscle. When gait was switched from a walk to a run and then to a sprint, the difference in the operating efforts between the muscles groups decreased but, still, the calf muscle worked at a 25 percent greater relative level than the quadriceps muscle.

Thus, regardless of whether we are walking or running, the calf muscle condition is likely a key determinant of our locomotor performance. Lower muscular reserve at the calf than quadriceps muscle level also provides insights into the age-related decline in muscle function that occurs at the ankle, rather than knee level, for all three modes of locomotion — walking, running and sprinting.

A crucial role of the calf muscles in locomotion should be considered when designing exercise interventions for improving walking and running ability. Luckily, training of the ankle propulsion capacity is very easy — just rise high on your toes or hop in the air.