Muscle-Activation Onset Times With Shoes and Foot Orthoses in Participants With Chronic Ankle Instability

Context

Participants with chronic ankle instability (CAI) use an altered neuromuscular strategy to shift weight from double-legged to single-legged stance. Shoes and foot orthoses may influence these muscle-activation patterns.

Objective

To evaluate the influence of shoes and foot orthoses on onset times of lower extremity muscle activity in participants with CAI during the transition from double-legged to single-legged stance.

Design

Cross-sectional study.

Setting

Musculoskeletal laboratory.

Patients or Other Participants

A total of 15 people (9 men, 6 women; age = 21.8 ± 3.0 years, height = 177.7 ± 9.6 cm, mass = 72.0 ± 14.6 kg) who had CAI and wore foot orthoses were recruited.

Intervention(s)

A transition task from double-legged to single-legged stance was performed with eyes open and with eyes closed. Both limbs were tested in 4 experimental conditions: (1) barefoot (BF), (2) shoes only, (3) shoes with standard foot orthoses, and (4) shoes with custom foot orthoses (SCFO).

Main Outcome Measure(s)

The onset of activity of 9 lower extremity muscles was recorded using surface electromyography and a single force plate.

Results

Based on a full-factorial (condition, region, limb, vision) linear model for repeated measures, we found a condition effect (F_3,91.8 = 9.39, P < .001). Differences among experimental conditions did not depend on limb or vision condition. Based on a 2-way (condition, muscle) linear model within each region (ankle, knee, hip), earlier muscle-activation onset times were observed in the SCFO than in the BF condition for the peroneus longus (P < .001), tibialis anterior (P = .003), vastus medialis obliquus (P = .04), and vastus lateralis (P = .005). Furthermore, the peroneus longus was activated earlier in the shoes-only (P = .02) and shoes-with-standard-foot-orthoses (P = .03) conditions than in the BF condition. No differences were observed for the hip muscles.

Conclusions

Earlier onset of muscle activity was most apparent in the SCFO condition for ankle and knee muscles but not for hip muscles during the transition from double-legged to single-legged stance. These findings might help clinicians understand how shoes and foot orthoses can influence neuromuscular control in participants with CAI.Key Words: footwear, insoles, ankle sprains, neuromuscular system, electromyography

Key Points

• Shoes and foot orthoses accelerated muscle-activation onset times of the ankle and knee but not the hip in participants with chronic ankle instability.
• Earlier muscle-activation onset times were most prominent in the shoes-with-custom-foot-orthoses condition.
• At the ankle, the muscle-activation onset time of the peroneus longus was earlier in the shoes-only, shoes-with-standard-foot-orthoses, and shoes-with-custom-foot-orthoses conditions than in the barefoot condition, and the muscle-activation onset time of the tibialis anterior was earlier in the shoes-with-custom-foot-orthoses condition than in the barefoot condition.
• At the knee, the muscle-activation onset times of the vastus medialis obliquus and vastus lateralis were earlier in the shoes-with-custom-foot-orthoses condition than in the barefoot condition.
• The results may help clinicians understand how shoes and foot orthoses can influence neuromuscular control of the lower extremity in participants with chronic ankle instability.

Lateral ankle sprains are estimated to account for approximately 15% of all sport injuries.¹ Even more concerning than the initial ankle sprain is the large proportion of patients with residual symptoms and recurrent ankle sprains for months to years after the initial injury.² The occurrence of repetitive ankle sprains and the feeling of the ankle “giving way” with slight or no perturbation has been defined as chronic ankle instability (CAI).³The transition task from double-legged to single-legged stance during barefoot (BF) conditions has been shown to discriminate between uninjured participants and participants with CAI. Researchers have reported that muscle-activation onset times typically were delayed^4,5 and postural stability was impaired⁶ in participants with CAI, indicating the use of another strategy to shift weight from double-legged to single-legged stance. However, it is unclear whether findings from BF tests represent typical daily situations when shoes, and for some persons foot orthoses, are often worn.The human foot is the first point of contact between the body and a supporting surface. The cutaneous mechanoreceptors on the planar surface of the foot are an important source of sensory information,⁷ which is considered essential for achieving and maintaining functional joint stability.⁸ Shoes and foot orthoses act as an interface between the body and a supporting surface and can influence the sensory feedback from these mechanoreceptors by increasing the contact area between the foot and the supporting surface.^7,9 Furthermore, the small kinematic alterations of the rear foot and tibia that have been described with the use of shoes and foot orthoses¹⁰ may put the ankle joint in a more neutral position, thereby improving the capacity of the ankle mechanoreceptors to provide more accurate proprioceptive input toward the central nervous system.¹¹ Changing the sensory input to these mechanisms consequently would change the motor output.⁷Evidence is increasing that shoes and foot orthoses can influence lower extremity muscle activation.^10,12–14 Dingenen et al¹⁴ were the first investigators to measure the influence of shoes and foot orthoses on muscle-activation onset times of the entire lower extremity in uninjured participants during the transition from double-legged to single-legged stance. Their results showed that shoes and foot orthoses can accelerate muscle-activation onset times of the peroneus longus. No differences were reported in more proximal muscles. Recently, researchers have suggested that future investigators should be focused on the influence of shoes and foot orthoses on neuromuscular control, especially in participants with injuries, such as CAI,^10,13,14 to increase our understanding of how positive clinical outcomes from the use of shoes and foot orthoses can be achieved.¹¹ Altering or improving proprioceptive information and muscle-activation patterns in participants with CAI would be clinically beneficial, given that their proprioceptive and neuromuscular deficits have been described.¹⁵To our knowledge, no investigators have focused on the influence of shoes and foot orthoses on muscle-activation onset times of the entire lower extremity in participants with CAI during the transition from double-legged to single-legged stance. Therefore, the purpose of our study was to evaluate the influence of shoes and foot orthoses on muscle-activation onset times during the transition from double-legged to single-legged stance in participants with CAI. Based on the proposed effects of shoes and foot orthoses on lower extremity neuromuscular control, we hypothesized that shoes and foot orthoses would accelerate muscle-activation onset times compared with a BF condition.