How to Evaluate and Improve Foot Strength in Athletes: An Update

Abstract

The foot is a complex system with multiple degrees of freedom that play an essential role in running or sprinting. The intrinsic foot muscles (IFM) are the main local stabilizers of the foot and are part of the active and neural subsystems that constitute the foot core. These muscles lengthen eccentrically during the stance phase of running before shortening at the propulsion phase, as the arch recoils in parallel to the plantar fascia. They play a key role in supporting the medial longitudinal arch, providing flexibility, stability and shock absorption to the foot, whilst partially controlling pronation. Much of the foot rigidity in late stance has been attributed to the windlass mechanism - the dorsiflexion of the toes building tension up in the plantar aponeurosis and stiffening the foot. In addition, recent studies have shown that the IFM provide a necessary active contribution in late stance, in order to develop sufficient impedance in the metatarsal-phalangeal joints. This in turn facilitates the propulsive forces at push-off. These factors support the critical role of the foot in providing rigidity and an efficient lever at push-off. During running or sprinting, athletes need to generate and maintain the highest (linear) running velocity during a single effort in a sprinting lane. Acceleration and sprinting performance requires forces to be transmitted efficiently to the ground. It may be of particular interest to strengthen foot muscles to maintain and improve an optimal capacity to generate and absorb these forces. The current evidence supports multiple exercises to achieve higher strength in the foot, such as the "short foot exercise," doming, toes curl, towing exercises or the more dynamic hopping exercises, or even barefoot running. Their real impact on foot muscle strength remains unclear and data related to its assessment remains scarce, despite a recognized need for this, especially before and after a strengthening intervention. It would be optimal to be able to assess it. In this article, we aim to provide the track and field community with an updated review on the current modalities available for foot strength assessment and training. We present recommendations for the incorporation of foot muscles training for performance and injury prevention in track and field.

Keywords: assessment; exercises; foot strengthening; intrinsic foot muscles; track and field athletics.

Figure 1

Measurement of the arch rigidity index.

Figure 2

Short foot exercise.

Figure 3

Short foot exercise with cross-body inversion focus (with written informed consent obtained from the subject).

Figure 4

Toe spread out exercise, 1st toe extension and 2nd to 5th toe extension.

Figure 5

Tower curl (Toe flexor exercise).

Figure 6

Short foot exercise in rotation (with written informed consent obtained from the subject).

Figure 7

Short foot exercise during propulsion (with written informed consent obtained from the subject).

Figure 8

Placement of electrodes for NMES on medial arch intrinsic foot muscles (McKeon and Fourchet, 2015).