Acute sensory and motor response to 45-s heavy isometric holds for the plantar flexors in patients with Achilles tendinopathy

Key points

1. 01A single session of heavy isometric calf holds did not lower pain during a functional task or improve pressure pain sensitivity.
2. 02Responses varied a lot between individuals rather than showing a consistent benefit.
3. 03The only measurable change was a small increase in concentric calf torque at one test speed.
4. 04Findings differ from patellar (knee) tendinopathy reports that suggested isometrics give quick pain relief.

How it was conducted

Design

Single-group before-and-after study (Level of evidence IV)

Participants

16 patients with Achilles tendinopathy (mean age 48.6, mean VISA-A 61.3)

Intervention

45-second heavy isometric plantar flexor (calf) contractions

Outcomes

Pain during a functional task (NRS), pressure pain threshold, and isokinetic plantar flexor torque, measured before and after

What they found

• 9 of 16 participants reported pain during the functional task.
• Pain on the numeric rating scale was 4.2 before versus 4.9 after, not statistically significant.
• Pressure pain threshold was 446.5 before versus 411.8 g/mm2 after, not statistically significant.
• Concentric plantar flexor torque at 90 degrees per second increased from 47.1 to 53.0 Nm (p=0.039); other test speeds were not significant.

Limitations

• Very small sample of only 16 patients with no control or comparison group.
• Single-group before-and-after design with low level of evidence (Level IV), so cause and effect cannot be confirmed.
• Only the immediate, acute response was measured, not longer-term outcomes.
• Individual responses varied widely, limiting how broadly the findings apply.

Why it matters

For patients

If you have Achilles tendinopathy, do not expect a single bout of heavy isometric calf holds to relieve your pain right away.

For clinicians

Heavy 45-second isometric holds should not be prescribed for immediate Achilles pain relief, as the knee-tendon pain-relief effect did not transfer here.

For readers

This small study suggests the quick pain-relief benefit reported for patellar tendinopathy isometrics may not apply to the Achilles tendon.