(Golden Oldie) Calf endurance and Achilles tendon structure in classical ballet dancers

Key points

1. 01The heel-rise test measures calf endurance by counting single-leg heel raises to fatigue and the total work performed.
2. 02Dancers performed about 74% of the total work of non-dancers and significantly fewer repetitions, indicating lower calf endurance.
3. 03Dancers reached a higher maximum heel-rise height, which the authors link to their shorter Achilles tendons rather than greater endurance.
4. 04Achilles tendon cross-sectional area and dorsiflexion range of motion did not differ between groups.
5. 05The authors suggest the heel-rise test could screen tendon health and inform return-to-dance decisions, but say a preventive calf-strengthening program would need to be tested in future trials.

How it was conducted

Design

Cross-sectional pilot study comparing dancers with non-dancers

Participants

20 healthy adults aged 16 to 35 (10 ballet dancers and 10 non-dancers, 2 male and 8 female per group); each lower extremity treated as a data point (20 limbs per group)

Intervention

No treatment; groups assessed with clinical exam, B-mode and extended field of view ultrasound, and the single-leg heel-rise test on a 10 degree incline

Outcomes

Achilles tendon length and cross-sectional area, dorsiflexion range of motion, VISA-A score, and heel-rise repetitions, maximum height, and total work

Analysis

One-way ANOVA between groups and Pearson correlation between heel-rise height and tendon length; significance set at p < 0.05

What they found

• Total work on the heel-rise test: dancers 1,643 (SD 492) J vs non-dancers 2,241 (SD 786) J (p = 0.014), about 74% as much work.
• Repetitions: dancers 19.7 (SD 3.6) vs non-dancers 32.5 (SD 8.29) (p < 0.001).
• Maximum heel-rise height: dancers 16.5 (SD 0.75) cm vs non-dancers 13.3 (SD 1.8) cm (p < 0.001).
• Achilles length to the gastrocnemius: dancers 18.4 (SD 1.75) cm vs non-dancers 20.2 (SD 2.6) cm (p = 0.016); length to soleus and cross-sectional area did not differ (p = 0.333 and p = 0.693).
• Maximum heel-rise height was negatively correlated with Achilles length to the gastrocnemius across both groups (R = -0.384, p = 0.017).

Limitations

• Very small sample (n = 20) and only 4 male dancers, limiting generalizability and sex-specific conclusions.
• Primarily pre-professional ballet students, so findings may not apply to professional dancers or other dance genres.
• Cross-sectional design cannot tell whether shorter tendons are an adaptive or a selective effect.
• One dancer with suspected compartment syndrome was excluded from the heel-rise test, further reducing that analysis.

Why it matters

For patients

If you are a ballet dancer, your calf may tire faster than expected even though you can rise high onto your toes, so calf endurance is worth attention.

For clinicians

The single-leg heel-rise test is a practical screening tool for calf endurance and tendon health in dancers, but normal values differ from those of other athletes, so return-to-dance criteria may need adjusting.

For readers

Ballet dancers reach higher on a heel-rise but do less total work, suggesting their lower leg adapts in ways standard athlete norms do not capture.