Hamstring strength vs. length: what should be the recovery priority following hamstring injury?

Hamstring strength vs. length: what should be the recovery priority following hamstring injury? Your weekly research review Contents of Research Review Background & Objective What They Did What They Found Practical Takeaways Reviewer’s Comments About ... Read more

James de Lacey

By James de Lacey
Last updated: March 15th, 2023
4 min read

Hamstring strength vs. length: what should be the recovery priority following hamstring injury?

Your weekly research review

James de Lacey

By James de Lacey
Last updated: March 15th, 2023
4 min read

Contents of Research Review

  1. Background & Objective
  2. What They Did
  3. What They Found
  4. Practical Takeaways
  5. Reviewer’s Comments
  6. About the Reviewer
  7. Comments

Background & Objective

Most acute hamstring strains which occur during sprinting involve the long head of the biceps femoris (BFlh) and the known risk factors for hamstring strain include age, strength deficits, flexibility, and fatigue. Additionally, a history of hamstring strains is a strong predictor. As such, it is necessary to investigate if there are activation deficits of the hamstring muscles and alternations in kinematics during maximum effort sprinting when hamstring strain has occurred.

Therefore, this study investigated the EMG activity of the BFlh and gluteus maximus (Gmax) muscles and the kinematic characteristics during overground sprinting in track athletes who had returned to sport following hamstring strain.

What They Did

For the purposes of this study, a hamstring strain was defined as an acute pain that was sustained during training or competition that prevents the player from participating in training or competition for at least a week. The time period after injury ranged from 2-61 months, with 1-6 months taken to return-to-sport of ten male college sprinters (age = 19.9 ± 0.3 yr) with a history of unilateral hamstring strain injuries.

Each participant performed a maximal effort sprint with passive markers and electrodes attached to their body to provide 3D kinematic data and EMG of the BFlh and Gmax muscles. After the sprinting trial, concentric strength assessments of bilateral hip and knee flexors and extensors were performed on a Cybex Isokinetic Dynamometer. Three consecutive maximum voluntary contractions were performed at velocities of 60°/s and 180°/s with 30 sec rest between sets.

What They Found

The key findings of this study included:
⇒ Mean sprinting velocity was 9.39 ± 0.17 m. s -1 .

⇒ No significant inter-limb differences were found in concentric strength.

⇒ During late swing phase, the activity of the BFlh in the previously injured leg was significantly lower than that in the uninjured limb.

⇒ Significant inter-limb differences were not noted in the Gmax muscle activation.

⇒ Knee flexion angle was significantly higher in the previously injured leg than the uninjured leg at 78 -82% of the sprinting gait cycle (one stride, late swing phase).

⇒ The BFlh length demonstrated significant reduction in the previously injured limb compared to the uninjured limb during late swing phase, while hip and knee torque during the sprinting gait cycle demonstrated no significant differences between limbs.

Practical Takeaways

The inter-limb difference observed in this study may reflect a shorter optimal fibre length of the previously injured hamstring muscles, indicating the BFlh had not fully recovered completely despite rehabilitation. Additionally, previous research has shown significantly lower eccentric knee flexion torque in the extended knee position (see HERE). This might suggest the importance of evaluating the function of the hamstring muscles, particularly during eccentric contraction in the lengthened position.

However, this is often not possible in sporting environments due to time and budget. Perhaps taking an interventional approach as in this case study (see HERE), where the weaker leg was targeted through extra hip extension work 3x/week for 6 weeks. Instead of targeting exclusively hip extension, the focus could be shifted towards eccentric hamstring contractions at long muscle lengths. For example, you could add 2x/week focused training as such:
Day 1: “Strength” Emphasis:
A1) Single Leg Romanian Deadlift 3-4×6-9.

B1) Single Leg Isometric Hamstring “Bosch” 3-4×5+5+5 sec.

Day 2: “Velocity” Emphasis:
A1) Alex Natera style cable 45° knee flexion performed with rapid ECC/
CON 3-4×5-8 (see HERE).

B1) Single Leg Drop Catch Back Extension 3-4×3-6 (see HERE).

Reviewer’s Comments

“Even though the exact location of the hamstring strains could not be identified, all of the participants showed decreased BFlh muscle activity which suggests that most sprinting type hamstring strains occur in the BFlh. Interestingly, concentric strength was not affected by previous injury, though running kinematics were. This may provide practitioners with improved rehabilitation strategies to effectively reduce the risk of re-injury.

Whether these particular athletes were more prone to injury is difficult to assess as they had a range of 2-61 months since their injury. Perhaps the sprinting itself, regardless of the altered kinematics acted as a potential vaccine to hamstring re-injury”.

Want to learn more?
Then check these out…

Watch this video
Read this article
Read this article
Listen to this podcast

The full study can be read here.

Want more research reviews like this?

Every coach understands the importance of staying up-to-date with the latest sports performance research like this, but none have the time, energy, or even enjoys spending hours upon hours searching through PubMed and other academic journals. Instead, your precious time is better-spent coaching, programming, and managing all the other more important aspects of your job.

The solution…

The Performance Digest
The Performance Digest is a monthly summary of the latest sports performance research reviewed by our team of hand-selected experts. We sift through the 1,000+ studies published in the realms of sports performance every, single month and review only those which are important to you. Each monthly issues contains 19 research reviews in all of the following disciplines:

  • Coaching Science
  • Strength & Conditioning
  • Technology & Monitoring
  • Fatigue & Recovery
  • Youth Development
  • Nutrition
  • Injury Prevention & Rehab
  • This comprehensive topic base ensures you’re constantly expanding your knowledge and accelerating your career as quickly as humanly possible. The reviews are also hyper-focused, 1-page summaries, meaning there’s no jargon or wasted time. We cut right to the chase and tell you what you need to know so you can get back to coaching.

    Join the thousands of other coaches who read it every, single month. Click here to grab your FREE copy…

    James de Lacey

    James de Lacey

    James was the Head Strength & Conditioning Coach for the Romanian Rugby Union. He has previously worked in America’s professional rugby competition Major League Rugby with Austin Elite and the NZ Women’s National Rugby League Team. He is a published author and has completed a MSc in Sport & Exercise Science from AUT, Auckland, NZ.

    More content by James

    Unlock 1,000+ Sports Science Studies For Free

    Access the latest research on Strength & Conditioning, Nutrition, Coaching, Recovery, Technology, Rehab, and Youth Development.

    Get Instant Access
    James de Lacey

    James de Lacey

    James was the Head Strength & Conditioning Coach for the Romanian Rugby Union. He has previously worked in America’s professional rugby competition Major League Rugby with Austin Elite and the NZ Women’s National Rugby League Team. He is a published author and has completed a MSc in Sport & Exercise Science from AUT, Auckland, NZ.

    More content by James
    Performance Digest

    Unlock 1,000+ Sports Science Studies For Free

    Get instant access to over 1,000 must-know sports science studies without paying a penny. You'll get the latest research on Strength & Conditioning, Nutrition, Coaching, Recovery, Technology, Rehab, and Youth Development.

    Get Instant Access