Atrophy and Hypertrophy After Hamstring Strain in Athletes

MR observations of long-term musculotendon remodeling following a hamstring strain injury. Silder A, Heiderscheit BC, Thelen DG, Enright T, Tuite MJ. Skeletal Radiol. 2008 Dec;37(12):1101-9.

The objective of this study was to use magnetic resonance (MR) imaging to investigate long-term changes in muscle and tendon morphology following a hamstring strain injury.
MR images were obtained from 14 athletes who sustained a clinically diagnosed grade I-II hamstring strain injury between 5 and 23 months prior as well as five healthy controls. Qualitative bilateral comparisons were used to assess the presence of fatty infiltration and changes in morphology that may have arisen as a result of the previous injury. Hamstring muscle and tendon-scar volumes were quantified in both limbs for the biceps femoris long head (BFLH), biceps femoris short head (BFSH), the proximal semimembranosus tendon, and the proximal conjoint biceps femoris and semitendinosus tendon. Differences in muscle and tendon volume between limbs were statistically compared between the previously injured and healthy control subjects.
Increased low-intensity signal was present along the musculotendon junction adjacent to the site of presumed prior injury for 11 of the 14 subjects, suggestive of persistent scar tissue. The 13 subjects with biceps femoris injuries displayed a significant decrease in BFLH volume (p < 0.01), often accompanied by an increase in BFSH volume. Two of these subjects also presented with fatty infiltration within the previously injured BFLH.
The results of this study provide evidence of long-term musculotendon remodeling following a hamstring strain injury. Additionally, many athletes are likely returning to sport with residual atrophy of the BFLH and/or hypertrophy of the BFSH. It is possible that long-term changes in musculotendon structure following injury alters contraction mechanics during functional movement, such as running and may contribute to reinjury risk.

My comments:

So on to this study. The abstract didn’t mean a lot to me before I took an in depth look at the anatomy. They found the LONG HEAD of the biceps femoris (the larger of 2 heads of the 3 muscles that make up the hamstrings) was generally what was strained in 13 out of the 14 injured, and was 10% smaller when measured between 5 and 23 months post injury. The biceps femoris SHORT HEAD was 13% larger. And the proximal conjoined tendon of the LONG HEAD biceps femoris and semitendinosus (another of the 3 hamstring muscles) was 85% larger. This was AFTER the athlete had completed their physical therapy and had returned to sport.

So what I learned from this is that the long head tendons being 85% larger is indicative of increased scar tissue that is still there as long as 23 months post injury. The LONG HEAD of the biceps does not recover full strength in spite of typical rehabilitation, but the SHORT HEAD becomes larger apparently to compensate for the injury of the LONG HEAD. Unfortunately the physical therapy rehabilitation exercises were not standardized so it’s unknown what exercise were performed. This meant something to me, but still not a lot until I looked up the particular attachments of the LONG HEAD and SHORT HEAD of the biceps femoris and saw that only the SHORT HEAD only crossed the knee joint and didn’t act at all to extend the hip, but only flexed the knee. The LONG HEAD in contrast crossed both the knee and the hip acting as both a hip extensor and a knee flexor.

So my thought is that these athletes were likely rehabilitated with hamstring strengthening exercises that act only on the knee, like leg curls, (both seated and prone) and to a lesser extent the Nordic Hamstring Curl, (which acts a lot at the knee and only a little at the hip). In contrast a Romanian Deadlift (RDL) acts primarily at the hip and I would expect would better target the LONG HEAD of the biceps femoris, and this might be what was missing from these athletes physical therapy protocols. SHORT HEAD atrophy of the biceps femoris, resulting from RDLs being a missing part of rehabilitation might also be why so many athletes, soccer players in particular injure and strain their hamstrings. It might also be why you test an injured athlete’s hamstring strength with knee flexion (a leg curl) and it might seem strong but they go right out and reinjure when running at high speeds, which requires strong hip extension.

So continuing to think out loud the Nordic Hamstring Curl has the advantage of particularly targeting eccentric strength of the hamstring, but the RDL being both eccentric and concentric does a better job at increasing strength in hip extension, plus better stretching the LONG HEAD, so the combination of the two exercises might be ideal. What I still don’t know is how strong an RDL an athlete should have in relation to their other exercises for safe return to sport, but based on my experience in therapy and at the NAU Weight room it should be AT LEAST as high as the persons back squat. But then you still get into problems of what kind of squat, high bar or low bar, how deep, etc. I also think this brings in need for isokinetic testing of hip extension both concentric and eccentric in normal players and players with hamstring strains much like it is done for the same muscle at the knee.

Further thinking out loud, it also gave me an idea for a new exercise I just made up called the “3 bounce RDL” where the person goes down to the bottom stretch position and bounces 3 times before returning upward. It might increase the eccentric strength component of the exercise and I think it most certainly will work to increase hamstring flexibility combined with strength. The problem I foresee however is that though you might stretch more, I don’t know if it would really cause any additional increase in eccentric strength as the athlete would almost certainly train with a lighter weight. So maybe it’s worthwhile only if the athlete has tighter hamstrings. Anyway makes me want to start looking for my own isokinetic muscle tester to one day gather dust and take up space in my office.

Thanks for reading my blog. If you have any questions or comments (even hostile ones) please don’t hesitate to ask/share. If you’re reading one of my older blogs, perhaps unrelated to neck or back pain, and it helps you, please remember Spinal Flow Yoga for you or someone you know in the future.

Chad Reilly is a Physical Therapist, obtaining his Master’s in Physical Therapy from Northern Arizona University. He graduated Summa Cum Laude with a B.S. Exercise Science also from NAU. He is a Certified Strength and Conditioning Specialist, and holds a USA Weightlifting Club Coach Certification as well as a NASM Personal Training Certificate. Chad completed his Yoga Teacher Training at Sampoorna Yoga in Goa, India.

4 thoughts on “Atrophy and Hypertrophy After Hamstring Strain in Athletes”

  1. Hi Chad,
    thanks for posting this. I had about 10 hamstring strains (BFLH) last 5 years. Try almost everything but nothing really helped. All types of stretching, all types of strenghtening, magnetic treatment, kinesiotaping, massages, acupuncture, etc. This year I found out that my right back thigh muscles looks different than left. Probably BFLH is atrophied. I do nordic curls, romanian deadlifts, bridge exercises etc. at least 3 times a week but it doesnt help. Can you recommend another exercise?
    Thank you for any advice.

    • Hi Dar,

      I have been wanting to do more blogs on recurrent hamstring strains because it is such a problem. It sounds like the exercises you are doing are mostly good, though I don’t think the bridges do much good, so I’m wondering if strength levels maybe are not enough yet. In my former pro but still league playing soccer player (who inspired my literature review and blogs) he was a striker so a pretty muscular player who was able to do hi-bar back squats to about or a bit above parallel (if I recall correctly) with 110 kg for 10 reps, and front squats (full) with 90 kg for 6, but in both cases I expect he was really stronger in his normal training, but I was trying to clean up some spine motion (flexion) I saw during his lifts, and work that spine flexion out of his RDLs as well.

      Subjectively, just looking at him I thought he looked like he should be able to do RDLs with 140 kg for 10 reps or so to be what I thought would be balanced for him, and hamstring strain proof, but that was just an educated guess on my part. When last seen he had worked up to 120 kg for 10 good reps and 140 kg for 8 reps (but I with range of motion not full) at which point he was continuing training on his own and had returned to play without any pain. Hamstring range of motion was full and symmetrical with a 90 degree straight leg raise bilaterally. Hamstring strength right vs left on a leg curl was the same also.

      We had settled in on what we thought were good lower body workouts, starting with a 10 minute warm-up on a stepmill. Then each workout (aiming for 3 times per week) he would start off with RDLs, then do nordic hamstring curls, then squats (he would alternate between front and back squats every other day), hip out & hip in machine. I had my guy doing 4-6 sets of 15-6 reps on the RDLs taking lots of smaller jumps to play it safe and avoid an re-injury in rehab, 3 sets of 10 on the nordic hamstring curls, 3 sets of 15 on the hip in and out machine (with the full 210 lb stack) then pulley hamstring stretches for 5 minutes. Then we were doing very hard EMS to his hamstrings with 4 large electrodes placed on each in a criss cross manner 10 seconds on, 50 seconds off, for 10 minutes, with his knees braced near full hamstring stretch on a seated leg curl machine.

      That said, I did hear from another soccer player that he was playing for a few months with without pain, but just recently had another strain and might be returning to therapy, but I haven’t talked with him yet to verify any details, or if he had kept up with his strength training.

      If my program missed anything maybe it was adding some calf training because the gastrocs do cross the knee and help with knee flexion so theoretically could take some load off the hamstrings at the end of the swing phase. The potential problem though is larger calf muscles make for a larger pendulum effect at the end of the leg, so ehh. Also I think I maybe could have formally implemented some sprint/agility drills into his program, and made that part of his pre-game warm-up routine, which I think would be a lot better than jogging and stretching but he felt good to go before we got to that point.

      The big problem with hamstring curls is there isn’t (that I have seen) any clear tests that people are ready to go back to playing sports or soccer. The isokinetic tests let you know what your strength ratios are, but unfortunately almost nobody has the equipment to do those tests. The other problem is that your hamstrings feel completely healed all day long, and generally feel fine during jogs and light to moderate runs, so generally the athlete and even the doctors think all is well with returning to sport. But the hamstring is only maximally stressed in sport with full on sprints, and pop. So that’s where I think track and field sprinters might have an advantage as they can really work up their pace and volume of training in a more graded and objective way than can a soccer player.

      In your case I’d be curious as to what sport you play, and what weights and reps you are working up to in the weight room, because the isokinetic testing indicated that you don’t just need to do the exercises you need to restore full and balanced strength. Otherwise maybe the missing part is graded sprint training, and a good pregame warmup, which I think might be better if it was based on short sprints rather than a bunch of stretches.

  2. Hi Chad,

    thanks for quick response. A lot to think about. I also play soccer, but now only on regional level. Still annoying to miss 5+ games every year. I strain my hamstring almost every year in April or May. Really dont undestand why. I do single leg RDLs. Do you prefer the “classic” RDLs better? I used EMS but never in stretched position. Very interesting idea. Agree that the balance between quads, hams, calfs is very important. Just finished reading Usain Bolts biography. He also had problems with hamstrings a the main reason was scoliosis (also had a little as a child). Its really hard to determine the right time to return. But I never reinjured right after rehabilitation. Usually 10 months later 🙂 I also prefer agility drills a gradual runs to sprint before static stretching. What do you think about kinesiotaping? Never really helped me. Placebo only? Thank you for all observations. Muscle strains are very common injury and theres so little information about it.

    • I think it’s good news that the strains are later rather than earlier in the season, and maybe that means you are getting strong enough in rehab early but just are not maintaining it throughout the season. So “maybe” making sure you keep up your strength training program throughout the season would make the difference.

      As for the single leg RDLs, the RDL was named after Nicu Vlad demonstrated them when he came to the United States in the 90s with his coach Dragomir Cioroslan and since they were Romanian the the term stuck. Dragomir was hired on as the head coach of the United States weightlifting team and to my knowledge neither of them did the exercise one legged, nor did the United States weightlifting team when Dragomir was coach. So I have only played around with the single leg version and my thoughts were that weights used just weren’t enough to maximally train the hamstrings like you get with the real RDL. Also whenever I see others use them it’s always with such I light weight that I doubt that there is much actual strengthening going on. So I would put the single leg RDL in the category with the bridges, which is likely not intense enough to do any good.

      Static stretching has been shown to decrease muscle strength, so it might be better to never do static stretching before play and just focus on warming up and dynamic stretching.

      As for kinesio tape, yeah I think it’s all placebo. I even did a blog on it, citing a meta-analysis that concluded kinesio tape probably didn’t to any good for any condition.


Leave a Comment

This site uses Akismet to reduce spam. Learn how your comment data is processed.