Rethinking Hamstring and ACL Injuries: Not Just “Sudden”, But Built Over Time
- Julian Simpson
- 2 days ago
- 3 min read
Rethinking Hamstring and ACL Injuries: Not Just “Sudden”, But Built Over Time
Sports injuries are traditionally divided into two categories:
Acute injuries, caused by a single traumatic event
Overuse injuries, caused by repeated loading over time
Hamstring strains and ACL tears are usually labelled as acute injuries because they often happen during a specific movement — a sprint stride or a sudden change of direction. But growing evidence suggests that many of these injuries may actually be overuse injuries that simply appear suddenly.
The Key Concept: Mechanical Fatigue
Biological tissues don’t need one massive force to fail.
Just like bending a paperclip repeatedly, muscles and ligaments can fail after many cycles of sub-maximal load if they don’t get enough time to recover. This process is called mechanical fatigue.
Damage starts at a nano- and microscopic level
Collagen structure gradually weakens
Eventually, the tissue fails during a normal movement — not an extreme one
This helps explain why an athlete can get injured during what looks like a routine sprint or landing.
Why Hamstring Injuries May Be Overuse Injuries
Research shows:
Hamstring injuries often occur during normal sprinting mechanics
Biomechanics in the “injury stride” are often no different from previous strides
Hamstring strains occur at sub-maximal speeds
Injury risk increases after sudden spikes in workload, not just absolute speed
Importantly, sprinting places the hamstrings under repeated eccentric loading, which is known to cause cumulative muscle damage — even when strain levels are well below the muscle’s maximum capacity.
MRI findings and lab studies show similar damage patterns between fatigue-induced muscle failure and real-world hamstring injuries, especially at the myotendinous junction.
Why ACL Injuries May Also Be Overuse Injuries
Although ACL tears are often described as catastrophic, several findings challenge that view:
Athletes perform hundreds of cutting and landing movements without injury
ACL tears often occur at moderate speeds
Cadaver and animal studies show that repeated ACL loading causes collagen damage
Human ACL tissue taken during reconstruction shows the same micro-damage patterns
ACL structure changes across a season, suggesting ongoing tissue stress
In some cases, ACL ruptures even occur without a clear traumatic event, further supporting a fatigue-failure model.
Why This Matters Clinically
If these injuries are viewed as purely “acute”:
They seem unpredictable
Monitoring load feels pointless
But if they are viewed as overuse injuries with sudden onset:
Load monitoring becomes critical
Recovery time matters
Injury prevention becomes possible, not reactive
This aligns with how we already manage:
Stress fractures
Tendinopathy
Throwing injuries in baseball
Practical Implications for Injury Prevention
Reframing hamstring and ACL injuries as overuse injuries supports:
✅ Smarter load management
Avoiding sudden spikes in sprinting, accelerations, or cutting
Managing cumulative exposure, not just peak effort
✅ Building tissue capacity
Increasing hamstring fascicle length
Improving muscle-tendon stiffness and control
Strengthening structures to tolerate repeated load
✅ Individualised risk assessment
Accounting for fatigue, recovery, biomechanics, anatomy, and health factors
Using wearable tech to estimate tissue-level loading (where possible)
The Big Takeaway
Many “sudden” sports injuries may actually be the final step in a long process of tissue fatigue.
By shifting how we think about hamstring and ACL injuries:
Prevention becomes proactive
Rehab focuses on capacity and recovery, not just strength
Monitoring load makes sense again
At a clinic level, this supports a whole-system approach — not just treating the injury, but managing how the body adapts to demand over time.
For more information about how we can help YOU with your sports performance and/or injury. Please call Health Wise Chiropractic 03 9467 7889 or book online to see one of our Chiropractors in Sunbury or Melton/Strathtulloh Today!
We are also really proud to offer our patients an APP for their Mobile- iPad. With access to your rehab exercises and our health tip blogs with over 600 articles.
Chiropractic has moved online. We offer our online program -STAND CORRECTED- To help you through the day.
We have over 30 programs on different health conditions
Each program contains
- Information about the conditions
- things to do and things to avoid
- nutrition advice
- all the stretches that are needed to help
Van Hooren B. Rethinking Acute Sports Injuries: Evidence for an Overuse Mechanism in Hamstring and ACL Injuries. Scand J Med Sci Sports. 2025 Oct;35(10):e70146. doi: 10.1111/sms.70146. PMID: 41078273; PMCID: PMC12516801.
Comments