Quick recap: Predicting Hamstring Strain Injury in Elite Athletes.

Citation: Brockett CL, Morgan DL, Proske U. Predicting hamstring strain injury in elite athletes. Med Sci Sports Exerc. 2004 Mar;36(3):379–87. doi: 10.1249/01.mss.0000117165.75832.05.

Link: https://pubmed.ncbi.nlm.nih.gov/15076778/

Key findings:

· Athletes with a unilateral history of hamstring strain injury (HSI) produced their peak concentric knee flexor torque at shorter lengths (~12° difference) in their bad leg (~41°) compared to their good leg (~29°).

Example comparison of one participant between their previously injured leg to their contralateral uninjured leg. It is clear the previously injured leg produces peak torque at shorter lengths. In this one participant, they have a higher peak torque on their bad leg than their good.

· Healthy, control athletes produced their peak torque at similar lengths (~2° difference) on their left (~30°) and right (~28°) legs.

· Legs with a history of HSI were ~7% weaker than their contralateral, uninjured limb.

· These previously injured limbs were ~13% weaker than the left and right limbs of the healthy, control athletes.

· Quadricep to hamstring torque ratio’s, peak quadricep torque and quadricep angle of peak torque: not different between limbs of either group.

Example of one healthy athlete with no history of HSI. Comparison between left and right legs.

Implications:

· Long length weakness may reduce capacity to decelerate the forward swinging shank during terminal swing phase of running.

· It is assumed that we act eccentrically during this phase of running. This study used concentric measures (as it is the traditional way to assess this torque-joint angle (TJA) relationship). Therefore requires further understanding around eccentric angle of peak torque production (not easy. Eccentric TJA relationship tend to be moreso: inc in length, inc in torque. Plateau in torque production more from running out of ROM or discomfort from the “stretch”).

· Reduced ability to produce force at long muscle lengths — increase susceptibility to damage at these longer lengths? — add repeated efforts (such as sprinting) — significant impact on injury likelihood?

· Can we shift this TJA relationship? If so how? Proposed that eccentric exercise useful in pushing curve to the right (more on this in future reviews).

Overview:

· Two groups.

o Previously injured group (one good leg and one bad leg — returned to full training program (currently healthy, but with HSI history in past season)): n=9; 8 male and 1 female. 5 of the males were AFL players, remainder track and field athletes.

o Healthy controls (no history of HSI): n=18; all male and all AFL players

· Concentric assessment of knee flexor and extensor torques during slow (60deg/s) contractions.

· Comparisons made within group, not between.