(Golden Oldie) Acute hamstring injuries in Swedish elite sprinters and jumpers: a prospective randomised controlled clinical trial comparing two rehabilitation protocols

Key points

1. 01Lengthening protocol (L-protocol) mean return: 49 days vs conventional (C-protocol) mean 86 days, a statistically significant difference (p<0.001, d=-1.21).
2. 02Proximal free tendon involvement substantially prolonged recovery in both groups: L-protocol 73 vs 31 days with vs without tendon injury; C-protocol 116 vs 63 days.
3. 03Re-injury rate was 3.6% (2 of 56) over 12 months, both in the C-protocol, compared with historically reported rates of 14-25%.
4. 04MRI-negative athletes (no visible injury on scan) returned in a mean of 15 days, significantly faster than MRI-confirmed sprint injuries in the L-protocol (mean 45 days, p<0.001).
5. 05Closer proximity of the injury or peak palpation pain to the ischial tuberosity and longer oedema length both correlated strongly with longer recovery times.

How it was conducted

Design

Prospective randomised controlled clinical trial

Participants

56 Swedish elite sprinters and jumpers (46 sprinters, 10 jumpers) with MRI-confirmed acute hamstring injury; recruited January 2009 to February 2012

Groups

L-protocol (n=28): lengthening-focused exercises (Extender, Diver, Glider); C-protocol (n=28): conventional exercises (contract-relax stretch, cable-pendulum, pelvic lift)

Primary outcome

Days from injury to return to full participation in training

Secondary outcome

Re-injury rate at 12 months post-return

MRI

All athletes had 1.5 Tesla MRI within 5 days of injury to confirm and characterise the injury

What they found

• Time to return: L-protocol mean 49 days (SD 26, range 18-107) vs C-protocol mean 86 days (SD 34, range 26-140), p<0.001, Cohen's d=-1.21.
• For injuries not involving the proximal free tendon: L-protocol mean 31 days vs C-protocol mean 63 days, p<0.01, d=-1.76.
• For injuries involving the proximal free tendon: L-protocol mean 73 days vs C-protocol mean 116 days, p<0.01, d=-2.12.
• Re-injuries over 12 months: 2 of 56 athletes (3.6%), both in the C-protocol, at 88 and 120 days post-initial injury.
• MRI-negative group (n=8, all L-protocol): mean return 15 days (SD 3, range 11-19) vs MRI-confirmed sprint injuries in L-protocol mean 45 days (SD 22, range 18-99), p<0.001, d=-1.59.
• Stretching-type injuries (n=4): mean return 121 days (range 106-140 days).
• Spearman correlations with time to return: distance from proximal injury pole to ischial tuberosity r=-0.895 (L) and r=-0.896 (C), both p<0.001; oedema length r=0.851 (L) and r=0.662 (C), both p<0.001; palpation distance r=-0.885 (L) and r=-0.775 (C), both p<0.001.
• 29% of L-protocol athletes (8 of 28) vs 68% of C-protocol athletes (19 of 28) needed to extend rehabilitation due to insecurity on the Askling H-test.

Limitations

• No blinding of the supervising clinician (the same person conducted all examinations and protocol supervision), which increases the risk of performance bias.
• Quasi-randomisation method (alternation after an initial dice roll within strata) is weaker than full concealed randomisation.
• Sample is limited to Swedish elite sprinters and jumpers, limiting generalisability to recreational athletes or other sports.
• Only four stretching-type injuries were included, making subgroup analysis for that injury type statistically underpowered.

Why it matters

For patients

Elite track and field athletes who sustain a hamstring strain can expect to return to full training approximately six weeks sooner if they follow a rehabilitation program focused on loading the muscle at long lengths rather than conventional exercises.

For clinicians

Clinicians should prioritise lengthening-based eccentric exercise protocols for hamstring rehabilitation in sprinters and jumpers, and use MRI and palpation proximity to the ischial tuberosity to counsel athletes on expected recovery timelines.

For readers

This trial provides moderate-quality evidence that the type of rehabilitation exercise, not just the presence of supervised rehab, meaningfully changes outcomes after hamstring injury in elite sprinting and jumping athletes.