Hamstring Strains: Why They Keep Coming Back

Hamstring Strains: Why They Keep Coming Back

Hamstring strains are the most common muscle injury in sprint-based sports, and their recurrence rate is a persistent clinical problem. Roughly one third of hamstring strains recur within the first year of return to sport — often more severely than the initial injury.¹ This pattern isn't bad luck. It reflects a rehabilitation process that declares the athlete ready before the tissue actually is.

The hamstrings — biceps femoris, semimembranosus, and semitendinosus — are bi-articular muscles that cross both the hip and the knee. They are responsible for hip extension, knee flexion, and critically, eccentric deceleration of the swinging leg during running. This last function is where most acute strains occur: in the late swing phase of sprinting, when the hamstring is working eccentrically at high load to decelerate the extending knee and prepare for ground contact.²

Why They Happen

The most common site of injury is the proximal biceps femoris, near its attachment to the ischial tuberosity. This region is under the highest eccentric stress during high-speed running, and it's the area that tends to be most vulnerable when the muscle hasn't been adequately prepared for sprint-specific loading.

Risk factors include previous hamstring injury (by far the strongest predictor), inadequate rehabilitation from the prior injury, insufficient eccentric strength relative to the demands of the sport, fatigue, and — consistently across the literature — a rapid increase in high-speed running volume without sufficient preparation of the tissue.³ This is the Gabbett pattern again: the acute load (specifically high-speed running metres) exceeds the chronic capacity of the tissue.

The Rehabilitation Gap

The recurrence problem in hamstring injuries largely reflects a rehabilitation gap: the athlete becomes pain-free and returns to sport, but pain-free is not the same as load-tolerant. The hamstring may feel normal during jogging, change of direction, and even moderate-paced running — but have insufficient eccentric strength and tendon capacity to handle the loads of sprint-specific work.

Specific eccentric hamstring strength — particularly at long muscle lengths (near full hip flexion) — is a critical but often underdeveloped component of hamstring rehabilitation. The Nordic hamstring exercise is the most studied intervention for both treatment and prevention, and trials consistently show it reduces hamstring injury rates by 50% or more when implemented in team sports.⁴ Yet it remains underused, partly because it's uncomfortable and partly because its benefit requires sustained, consistent practice over months, not weeks.

What Recovery Actually Requires

Effective hamstring rehabilitation moves through distinct phases: initial load reduction and pain management, progressive strengthening (isometric → isotonic → eccentric at increasing muscle lengths), running re-introduction at controlled speeds, and finally sprint and change-of-direction work at progressive intensities. Each phase requires adequate time — not because the muscle feels sore, but because the tissue adaptation to high-load eccentric work takes weeks to months to accumulate.²

Return-to-sprint criteria — not calendar time — should determine readiness. These typically include: >90% eccentric strength symmetry, completion of a graded sprint program without symptom reproduction, and passing sport-specific agility and speed tests. Meeting these criteria takes considerably longer than most athletes expect: twelve to sixteen weeks from injury for a significant biceps femoris strain is realistic for full sprint clearance.

Prevention: The Nordic Hamstring Exercise

For team sport athletes and recreational runners, the Nordic hamstring exercise — performed twice weekly during the season — represents one of the highest evidence-to-implementation ratio interventions in sports medicine.⁴ It is demanding, it requires progressive loading, and it works. The mechanism is straightforward: it develops eccentric strength at long muscle lengths, precisely the capacity that fails in the late swing phase of sprinting.

There are no dangerous exercises for the hamstring — only progressions that move too quickly for the tissue.³ The Nordic is highly provocative when introduced too aggressively; introduced progressively over four to six weeks, it is the most evidence-supported hamstring injury prevention tool available.

At Boreal Spine & Sport, hamstring rehabilitation includes assessment of the full lower limb kinetic chain — hip extension capacity, pelvic control, running mechanics — alongside progressive eccentric loading, to address the factors that drove the injury in the first place and build the tissue capacity for a genuine return to sport.

References

1. Arnason A, Andersen TE, Holme I, Engebretsen L, Bahr R. Prevention of hamstring strains in elite soccer: an intervention study. Scand J Med Sci Sports. 2008;18(1):40–48.
2. Askling CM, Tengvar M, Saartok T, Thorstensson A. Acute first-time hamstring strains during high-speed running. Am J Sports Med. 2007;35(2):197–206.
3. Gabbett TJ. The training-injury prevention paradox: should athletes be training smarter and harder? Br J Sports Med. 2016;50(5):273–280.
4. van der Horst N, Smits DW, Petersen J, Goedhart EA, Backx FJ. The preventive effect of the Nordic hamstring exercise on hamstring injuries in amateur soccer players. Am J Sports Med. 2015;43(6):1316–1323.