Update On Hamstring Injuries

Previous published research defined 2 main types of hamstring injuries. Sprint type (which usually occurs while sprinting hard) and slow-stretch type which occur during movements leading to excessive lengthening of the hamstrings. For example during high kicking, doing a split during taekwondo training or sliding tackles during football. You can read more here.

These 2 different mechanisms of injury affects functional deficits, injury location and return to sport time. 

Sprint related hamstring injuries typically occurs during late swing phase. The bicep femoris is usually the muscle injured and tends to present more severely at first, but allows a quicker return to sport (RTS). 

Stretch-type injuries which often involved semimembranosus muscle typically have a less severe initial presentation, but take longer to RTS. They normally occur in a position of excessive hip flexion with a hyperextended knee (pictured below).

Picture from Zentrum Sports

2 studies using systematic video analyses published in 2022 provided new insight into hamstring injuries as they examined the role of the trunk (or torso) during agility and evasion movements in field sports where hamstring injuries abound.  

Kerin et al (2022) described professional rugby injuries occurring in 5 distinct patterns - kicking, running, decelerating, while tackling and in the ruck.The authors also observed that trunk flexion and ipsilateral (same side) rotation along with knee extension at the point of injury.

Gronwald et al (2022) studied hamstring injuries in elite German soccer players and showed that stretch type injuries occurred during kicking and braking (while running) and were frequently caused by indirect contact from an opponent (contact to the body not the hamstring). 

It is also interesting to note that unlike previous studies, Gronwald et al (2022) found that most stretch type hamstring injuries involved the bicep femoris instead of semimembranosus. The authors also found that T-junction hamstring injuries (where the long and short head biceps femoris merges) have the highest re-injury rate. They usually occur in late swing (or early stance) phase, with ipsilateral trunk rotation (while catching a pass, tackling, reaching for a ball or looking behind). 

Knowledge of hamstrings injuries have definitely evolved with recent publications describing multiple scenarios and types of hamstrings injuries.  Previous prevention strategies to train the hamstrings muscles in late swing phase may be insufficient. We should now also give some consideration to the trunk (torso) in different planes to reduce injury incidence. This involves training hamstring strength when the muscle is in a lengthened position while the trunk and knee are in flexion. 

References

Kerin F, Farrell G, Tierney P et al (2022)> It's Not All About Sprinting: Mechanisms Of Acute Hamstring Injuries In Professional Male Rugby Union- A Systematic Visual Video Analysis. BJSM. 56(11): 608-615. DOI: 10.1136/bjsports-2021-104171.

Gronwald T, Klein C, Hoenig T et al (2022). Hamstring Injury Patterns In Professional Male Football (Soccer): A Systematic Video Analysis Of 52 Cases. BJSM. 56(3): 165-171. DOI: 10.1136/bjsports-2021-104769.