Morton Toe and Neuromuscular Performance

Morton toe is a congenital foot morphology characterized by a longer second metatarsal relative to the first. Although traditionally regarded as a clinical or orthopedic variation associated with metatarsal stress fractures and balance difficulties, limited evidence from sprinter populations suggests that a longer second toe may be associated with superior athletic performance. However, no previous study has examined whether Morton toe morphology is related to neuromuscular contractile properties assessed via tensiomyography or kinetic performance derived from force plate testing in a controlled group comparison design.

Participants were screened from 97 female football players. Exclusion criteria included BMI outside the 18.5-29.9 range, bilateral arch index outside the 14-29% range, inconsistent bilateral foot morphology, lower-extremity injury within the past 12 months, neurological or orthopedic conditions, performance-affecting pharmacological use, and menstruation on the measurement day. Morton toe classification was based on the palpation method described by Davidson et al. (2007) with a minimal detectable change threshold of ±0.30 mm.

All measurements were conducted during the off-season to minimize training load interference. Testing followed a standardized sequence: foot morphology assessment, tensiomyography of the dominant vastus lateralis at rest, a 15-minute warm-up, and a 40-cm drop jump test. The assessor was blinded to group classification, and statistical analysis was performed by an independent researcher on a coded dataset. Primary outcome variables (Tc and RSI) were determined a priori. Secondary outcomes were corrected for multiple comparisons using the Holm-Bonferroni method. Regression analyses were performed to assess the independence of group effects from age, body mass index, and mean bilateral arch index.

Primary outcomes

• Contraction Time (Tc) [Single measurement session]: Tensiomyographic contraction time of the dominant vastus lateralis muscle, defined as the time between 10% and 90% of maximal radial displacement (ms).
• Reactive Strength Index (RSI) [Single measurement session]: Jump height divided by ground contact time during a 40-cm drop jump test (m/s). The trial with the highest RSI value out of three attempts was selected for analysis.

Secondary outcomes

• Maximal Displacement (Dm) [Single measurement session]: Peak radial displacement of the vastus lateralis muscle belly during tensiomyographic measurement (mm).
• Relaxation Time (Tr) [Single measurement session]: Time from 90% to 50% of maximal displacement during the relaxation phase of tensiomyographic measurement (ms).
• Delay Time (Td) [Single measurement session]: Time from electrical stimulus onset to 10% of maximal displacement during tensiomyographic measurement (ms).
• Sustain Time (Ts) [Single measurement session]: Duration the muscle response remains above 50% of maximal displacement during tensiomyographic measurement (ms).
• Jump Height (JH) [Single measurement session]: Vertical jump height calculated from flight time during a 40-cm drop jump test (cm).
• Peak Power Normalized to Body Mass (PPI) [Single measurement session]: Peak power output normalized to body mass during a 40-cm drop jump test (W/kg).
• Landing Net Peak Force Normalized to Body Mass (LPF) [Single measurement session]: Peak vertical ground reaction force at landing normalized to body mass during a 40-cm drop jump test (N/kg).

Sex: Female, ages: 18 Years to any, accepts healthy volunteers

Inclusion Criteria:

* Active female football players with a valid sports license for the current season
* Regular participation in training and competitive matches
* Bilateral Morton toe morphology (Δ ≤ -0.30 mm on both feet) or bilateral normal foot morphology (Δ > +0.30 mm on both feet)
* Body mass index between 18.5 and 29.9 kg/m²
* Bilateral arch index between 14% and 29%
* Voluntary participation with written informed consent

Exclusion Criteria:

* Serious lower-extremity musculoskeletal injury within the past 12 months
* Neurological or orthopedic disease affecting measurement procedures
* Current use of pharmacological products affecting performance
* Acute pain, injury, or illness on the measurement day
* Menstruation on the measurement day (self-reported)
* Inconsistent bilateral foot morphology classification between feet
* Bilateral arch index below 14% (high arch) or above 29% (low arch)

• Study Protocol (PDF, 2025-11-05)