Hamstring strains and cramps

The hamstrings are the most commonly strained muscle group in running sports, and they have the highest recurrence rate of any soft tissue injury. Somewhere around a third of hamstring strains happen again within a year, usually because the first one was rehabilitated to the point of being comfortable rather than to the point of being strong.

Two different injuries

Sprint-type. The common one. Occurs at high speed, usually in the late swing phase as the leg reaches forward and the hamstring is contracting while lengthening. Pain is typically in the belly of the biceps femoris, in the middle of the back of the thigh.

Stretch-type. Occurs with a slow, extreme stretch — a high kick, a slide tackle, a dancer’s split. Pain is usually higher, close to the sitting bone, and involves the semimembranosus tendon.

Stretch-type injuries take considerably longer to recover, often two to three times longer, and knowing which you have from the outset avoids a great deal of frustration.

What happens at the time

A sudden sharp pain at the back of the thigh, usually stopping you immediately. Sometimes a pop. Bruising may appear over the following days, often lower down the leg than the injury as blood tracks with gravity.

Signs of a more severe injury: inability to walk without significant limp, a palpable gap in the muscle, or bruising that is extensive and immediate. Those warrant prompt assessment and sometimes imaging.

A tear at the very top, at the sitting bone, that comes with numbness down the leg or an inability to bend the knee against resistance may be a proximal avulsion — the tendon pulling off the bone — which is one of the few hamstring injuries that sometimes needs surgery, and it is time-sensitive.

The first few days

The old RICE advice has softened. Current thinking:

• Protect — avoid movements that hurt, use crutches for a day or two if walking is significantly painful
• Optimal loading — gentle pain-free movement early rather than complete immobility. Muscle heals better with some load
• Ice for comfort if it helps, not because it speeds healing
• Compression and elevation to manage swelling
• Avoid aggressive stretching and deep massage in the first few days, which can worsen bleeding into the muscle

Rehabilitation, and where it usually goes wrong

The single most important point: getting out of pain and getting strong are different milestones, and most re-injuries happen in the gap between them.

A well-constructed programme includes:

Progressive strengthening, especially at length. Nordic hamstring curls have the best evidence of any single intervention for preventing hamstring injury — reductions of around half in the studied populations. Exercises that load the muscle in a lengthened position matter more than exercises that load it short.

Eccentric loading. The hamstring fails while lengthening under load, so that is the situation rehabilitation has to prepare it for.

Running progression. Straight-line jogging, building to strides, then to near-maximal sprinting. Returning to sport without having sprinted in rehabilitation is returning untested to the exact mechanism that caused the injury.

Trunk and pelvic control. Hamstring function depends on how the pelvis is controlled, and this is often the missing piece in a recurrent case.

Objective return criteria. Strength testing against the other leg, full pain-free range, and sprinting at full speed without apprehension — rather than a date on a calendar.

Timeframes

A minor sprint-type strain: two to four weeks. A moderate one: six to eight. Stretch-type injuries near the sitting bone: three months or more, and sometimes considerably longer.

These ranges are wide because the injuries genuinely vary. What does not vary is that returning early is the strongest predictor of doing it again.

Cramp is a different problem

Hamstring cramp — a sudden, involuntary, intensely painful contraction — is not a strain and does not indicate damage.

The traditional explanation is dehydration and electrolyte depletion. The evidence for that is weaker than commonly assumed. The better-supported model is neuromuscular: cramp occurs when a fatigued muscle’s reflex control becomes altered, with excitatory drive increased and inhibitory feedback reduced. Which is why cramp appears at the end of long efforts and at intensities above what you have trained for.

What helps:

• Passive stretching during the cramp — the most reliable immediate remedy, and consistent with the neuromuscular model
• Training at the intensity and duration you intend to compete at, so fatigue arrives later
• Adequate conditioning of the muscle
• Fluid and sodium, which makes a difference for some individuals, particularly heavy sweaters in the heat — worth attending to, not the whole answer

Frequent cramping unrelated to exercise, cramps with muscle weakness or wasting, or cramps that are new and persistent are worth a medical review — they can reflect medication effects, metabolic problems or neurological conditions.