Master List of Rehab Meta-Analyses

Master List of Rehab Meta-Analyses

       This article was inspired by Greg Nuckols' article that archives and gives brief interpretations of many of the meta-analyses relevant to the area of strength and hypertrophy development. This is an exceptional way to get a evidence-grounded birds-eye-view of a given field, although there is certainly nuances that can be lost if you only consider meta-analytic data. If you are not familiar with what a meta-analysis is I strongly suggest you read the introduction to Greg's article as understanding the hierarchy of evidence is critical for anyone wanting to use science to improve their understanding of the world. 

Without further ado, here is a running (and continually expanding) list of meta-analyses relevant to the field of sports and orthopedic rehab. Let me know in the comments what I am missing or if you have feedback on any of my interpretations! 

Table of Contents

Pathology Specific

Muscle Strains 

Including the Nordic hamstring exercise in injury prevention programmes halves the rate of hamstring injuries: a systematic review and meta-analysis of 8459 athletes. van Dyk et al. (2019)

ACL 

The Effects of Injury Prevention Programs on the Biomechanics of Landing Tasks: A Systematic Review With Meta-analysis. Lopes et al. (2017) 

 

Modalities

Effect of blood‐flow restricted vs heavy‐load strength training on muscle strength: Systematic review and meta‐analysis. Grønfeldt et al. (2020)

Epidemiology

The epidemiology of injuries across weight-training sports. Keogh and Winwood (2017)

Injury Prevention

Laureson 2016 + 2018

Modalities

Effect of blood‐flow restricted vs heavy‐load strength training on muscle strength: Systematic review and meta‐analysis. Grønfeldt et al. (2020)

Pathology Specific

Muscle Strains 

Including the Nordic hamstring exercise in injury prevention programmes halves the rate of hamstring injuries: a systematic review and meta-analysis of 8459 athletes. van Dyk et al. (2019) - Interpretation taken directly from Stronger by Science

The title of this meta-analysis is shockingly self-explanatory. Nordic curls dramatically decrease the risk of hamstrings strains in athletes.

ACL

The Effects of Injury Prevention Programs on the Biomechanics of Landing Tasks: A Systematic Review With Meta-analysis. Lopes et al. (2017)  - Interpretation taken directly from Stronger by Science

Injury prevention programs aimed at altering biomechanical profiles associated with ACL injury risk seem to be effective. Specifically, they seem to help increase knee and hip flexion angles during landing tasks (meaning people are absorbing force more effectively, rather than getting a big “shock” when they land), and decrease knee abduction moments (knee caving). The fact that landing mechanics are trainable is important information for coaches who train athletes (specifically female athletes in sports that require a lot of jumping).

Modalities

Effect of blood‐flow restricted vs heavy‐load strength training on muscle strength: Systematic review and meta‐analysis. Grønfeldt et al. (2020) - Interpretation taken directly from Stronger by Science

Low-load training (20-50% 1RM) with blood flow restriction produces strength gains that are not significantly different from strength training without blood flow restriction in more traditional intensity ranges (60-90% 1RM). However, the mean effect leans in favor of heavier training without BFR, and the difference would likely be larger in well-trained populations. However, if gaining strength is a primary training goal, and you choose to do low-load training for some reason, using BFR for your low-load training may not be a bad idea. A slightly older meta-analysis did find a significant difference in strength gains in favor of heavier traditional training; it also found that low-load training the BFR and heavier traditional training led to similar muscle growth.

Epidemiology

The epidemiology of injuries across weight-training sports. Keogh and Winwood (2017) - Interpretation taken directly from Stronger by Science

Bodybuilding has the lowest injury risk (0.24-1 injuries per 1,000 hours) and strongman and highland games have the highest injury risk (4.5-7.5 injuries per 1,000 hours), while weightlifting and powerlifting fall in the middle.

Spinal Surgery vs Conservative Care

Seeking Input for Future Blog Posts

Below are some articles and topics whose messages I believe have a relatively large impacts on best practice for various areas of performance and health devlopement. Please post in the comments if you would like to see one written about or a topic that I have not listed here. Thanks for the feedback🙏! 

Research Articles:

Which Specific Modes of Exercise Training Are Most Effective For Treating Low Back Pain: A Network Meta-Analysis - Owen 2019

TLDR - they all work to a similar extent, reducing pain  approximately 3/10 on average and improving function on average 15% (as measured by the Oswestry Disability Index ). Just get your (or your patient's) butt moving in whatever way they can adhere best to. However there are some interesting nuances here that would be worth diving into.

Ground Reaction Force Metrics Are Not Strongly Correlated With Tibial Bone Load When Running Across Speeds and Slopes: Implications for Science, Sport and Wearable Tech - Matijeviche 2019
Axioms regarding the connection between certain ground reaction force measures (GRFs) and bone loading (and thus parameters that affect bone stress injury risk) have been systematically misrepresented both in the literature and in commercial wearable technology. Specifically, when measuring tibial bone load at different speeds and slopes, typical GRF metrics such as the average vertical loading rate, impact peak, and total vertical impulse were not well (and often negatively 😲!) correlated with with tibial bone stress, although peak GRF of the entire stance phase was somewhat good at predicting bone load (r=.7). As an intuitive example of how this works, tibial strain goes up significantly when running uphill because of the increased demand on the calf and associated muscular contribution to tibial strain, although GRF metrics are generally low (i.e. footsteps tend to be quieter running up hills). This means that the conclusions of a large portion of salient literature must be re-interpreted and that the recommendations given by many wearable products may provide dangerous recommendations to those at risk for bone stress injuries.

The Relationship Between Training Load and Injury in Athletes: A Systematic Review - Eckard 2018

A systematic review that anchors the importance of both internal and external training load in the prevention of injury.

The effectiveness of exercise interventions to prevent sports injuries: a systematic review and meta-analysis of randomised controlled trials - Lauersen 2016

A systematic review that anchors the MASSIVE importance in resistance training to prevent acute and overuse injury, and the relative lack of importance of stretching and "neuromuscular exercises". 

Topics:

Placebo and Nocebo in Physical Therapy and Health Care, Ethical Considerations

Running Shoe Selection Guide

Core Principles to Safe Effective Strength Training ala Powerlifting

Interval Training Guide 

Chris Johnson and Steve Sattigast Running Coaching Cohort - A Review

Journal Club - Sun et al 2020_Footwear Construction and Running Biomechanics

Running Shoe Anatomy and The Evidence

Systematic Review of the Role of Footwear Construction in Running Biomechanics: Implications for Running-Related Injury and Performance - Sun et al., 2020

Summery of Main Findings:

- Softer and thicker stacks tend to decrease impact parameters likely increasing comfort levels; mixed results lean to hard midsoles improving performance parameters

- Decreased drop increases relative demands on the ankle and calf and increased drop increases relative work of the knee; selection may therefore be largely influenced by injury history

- Minimalist shoes have the same effects on relative joint loading as decreased drop, as well as documented improvements in performance which are contributed to by their light weight and tendency to cause runners to shift to more mid/forefoot striking

- Shoe bending stiffness is significantly and reliably associated with improvements in variables associated with performance and should therefore be one of the main criteria when selecting shoes for performance

-Heel cups are effective for reducing plantar pressure in the heel and other variables associated with heel fat pad irritation and are therefore effective in managing this type of pain

This study is a good read to orient yourself to the various features of a running shoe and the evidence base to support their respective biomechanical effects. This information may contribute to shoe selection choices for performance and/or injury risk reduction. Below the results of each shoe characteristic investigated are interpreted.

Shoe bending stiffness -  Shoe bending stiffness was found to reliably and significantly improves performance whereby a stiff shoe absorbs and releases energy that would otherwise have to be attenuated/generated by the joints and muscles in the feet and primarily the first metatarsal phalangeal joint (MTPJ). In fact, the Nike Vaporfly 4% - which has a carbon plate built into the midsole to increase stiffness - has been demonstrated to improve running economy by 4% (hence the name) and has been widely hailed as the shoe that broke running due to its role in the the worlds top 5 marathon times (Hoogkammer et al., 2017). Since decreased MTPJ joint work is consistently measured in a stiff shoe, this feature is also likely to benefit those with MTPJ pathology such as turf-toe, hallux rigidus, or osteoarthritis in this joint. If you’re wondering what shoe stiffness actually is, just try bending the toes of one of your shoes up to touch the heel, and then compare to another shoe.

Midsole Characteristics - Of the 13 studies that looked at midsole hardness, 9 found positive effects on performance characteristics and 4 found no effect. Studies that found positive effect through increased hardness found this to be due to decreased energy lost in the MTPJ and decreased peak rearfoot eversion, a similar mechanism as the previously discussed with shoe bending stiffness. With regards to sole thickness and cushioning, all studies that investigated these characteristic found decreases in impact parameters implying improved comfort. Although not mentioned in the study the trade off of adding material to a shoe is increased weight, and weight is known to be one of the primary influencers of performance (Fuller et al., 2015). Therefore this section supports my heuristic that cushioned shoes with thick stacks are often good for comfort and are especially important for long distance training runs; whereas you may choose lighter variants for speed work and race day when comfort is not as important.  

Heel Flare - The single study examining heel flare (25 degrees, 0 degrees and rounded edge) found no kinematic differences between conditions. However there is a reasonable conceptual basis to believe that a lateral posterior heel flare in heel strikers would generally increase pronatory forces (through an increase in the lever arm at initial strike); therefore manipulation of this parameter may still be indicated in certain clinical scenarios.

Heel-Toe Drop - The results here were consistent and what one would expect, the larger the drop the more relative force was attenuated at the knee vs the ankle. Therefore considering medical history when selecting drop is very reasonable; if you have a history of knee pain perhaps go for lower drop and vis versa for ankle/foot pain. Interestingly the one clinical study comparing drop heights found no difference in injury rate, supporting my stance that although lay runners often attribute shoes to injury the nuances discussed in these biomechanical studies often have very small effects on overall injury risk (training load management, recovery, and injury history being much stronger determinants).

Minimalist Shoes - Although there is likely only a small - if any - overall injury-risk difference between shoe types what is evident through the research on minimalist shoes is that that the profile of injuries may change based off footwear characteristics. In the studies review they found minimalist shoes vs “conventional” running shoes caused increased load adaptation of the Achilles and showed other biomechanical indications of increasing relative load on the ankle and decreasing relative load on the knee. If this sounds similar to the heel-toe drop section that’s because a smaller drop is one of the characteristics a minimalist shoe. Another primary characteristic of a minimalist shoe is light weight, which we know to be associated with performance (Fuller et al., 2015). Minimalist shoe use was also associated with a transition to a forefoot strike technique which has also been associated with improved performance.  For further discussion of the role of footstrike on performance you can read more in my article running gait biomechanics. Considering these observations its unsurprising that this study also found a positive effect of minimalist shoes on performance.

Heel Cups - This was the first time I encountered scientific investigation of the heel cup and I was pleased to find that the two studies included in this review supported my clinical success using heel cups to decrease pain with plantar heel pain (I usually tell patients to buy a 5-15$ product off Amazon). And indeed, decreases in the the biomechanical stresses associated with plantar heel pain (such as plantar pressure) and self reported pain were reduced. It’s important to note that this benefit applies to irritation of the plantar heel tissues (ie plantar fat pad and possibly the calcaneal periosteum) and not the plantar fascia. Although I have always prescribed gel or rubber heel cups, one study compared rubber to plastic and plastic did a better job of preserving heel pad thickness, something that I will have to experiment with in my clinical practice moving forward.

Although this article exclusively focused on the biomechanical consequences of various shoe characteristics it is important to keep in mind the overall role of running shoes in performance and injury-risk reduction in order to prioritize our resources accordingly. Currently there is not sufficient evidence to support the idea that traditional shoe prescription methods can reduce injury, and the varience of performance effects are also quite small. Therefore, for the vast majority of un-injured runners, comfort and cost should be the primary considerations with shoe selection. For further discussion and substantiation of these points please read my running shoe selection bible.

Citations

Hoogkamer, W., Kipp, S., Frank, J. H., Farina, E. M., Luo, G., & Kram, R. (2017). A Comparison of the Energetic Cost of Running in Marathon Racing Shoes. Sports Medicine, 48(4), 1009–1019. doi: 10.1007/s40279-017-0811-2

Fuller, J. T., Bellenger, C. R., Thewlis, D., Tsiros, M. D., & Buckley, J. D. (2014). The Effect of Footwear on Running Performance and Running Economy in Distance Runners. Sports Medicine, 45(3), 411–422. doi: 10.1007/s40279-014-0283-6

 

Clinical Biomechanics and Gait Modification in Distance Running

I wrote this piece during PT school and it is something I am very proud of, both because of the effort put in and the product produced. At the time (and to this day) I was unable to find another single resource on this topic that so clearly and comprehensively reviewed the evidence base. As my understanding of the science progresses I realize some aspects of this piece need to be revised (a non-comprehensive list of the biggest revisions necessary is below) but to this day I stand by it as possibly the best single reference for a deep overview of the topic. Finally, of note is that I never made a bibliography for the article (I wrote this for barely any credit🤓and formatting citations is my least favorite thing IN THE WORLD) so if you want the citation information or research manuscripts feel free to contact me directly.

Most significant revisions necessary:

Ground Reaction Force Metrics Are Not Strongly Correlated With Tibial Bone Load When Running Across Speeds and Slopes: Implications for Science, Sport and Wearable Tech - Matejevich 2019
Axioms regarding the connection between certain ground reaction force measures (GRFs) and bone loading (and thus parameters that affect bone stress injury risk) have been systematically misrepresented both in the literature and in commercial wearable technology. Specifically, when measuring tibial bone load at different speeds and slopes, typical GRF metrics such as the average vertical loading rate, impact peak, and total vertical impulse were not well (and often negatively 😲!) correlated with with tibial bone stress, although peak GRF of the entire stance phase was somewhat good at predicting bone load (r=.7). As an intuitive example of how this works, tibial strain goes up significantly when running uphill because of the increased demand on the calf and associated muscular contribution to tibial strain, although GRF metrics are generally low (i.e. footsteps tend to be quieter running up hills). This means that the conclusions of a large portion of salient literature must be re-interpreted and that the recommendations given by many wearable products may provide dangerous recommendations to those at risk for bone stress injuries.

Click Here For - Clinical Biomechanics and Gait Modification in Distance Running 

Strength Training for Runners - The Why and How

Science Shows Strength Training Greatly Improves Endurance Running Performance! Learn the Why and How-To Here…

In science, the strongest type of evidence is called a “meta-analysis”. This is an analysis that looks at all of the existing studies that address a specific question (in this case, “does strength training improve running performance?”) and calculates the combined results of these studies. Two such meta-analyses have recently been released on the topic of strength training for runners and have shown that strength training is a vital part of any runners routine. Balsalobre-Fernandez et al. (2016) reviewed studies on high-level middle- and long-distance runners and found strength training provided a “large beneficial effect” for running economy when compared to those who did not strength train.  Running economy is the amount energy used at a given speed, i.e. running efficiency. Blagrove et al. (2018) performed a similar analysis however they included more novice runners, as only 6 months of previous training was required for studies to be considered. The following was observed: running economy improvements of 2-8%, improved time-trial performance (1.5-10k) and improvements in other anaerobic performance measures.

How they Trained

Both reviews found 2-3 strength training sessions a week of had the best outcomes and that a minimum of 4 weeks was required to see results. All the studies used either heavy resistance training, plyometrics, or combined protocols and none of the protocols were clearly superior to the others.  There were quite diverse training regimens used however below are some “average programs” based on the similarities within the training categories. As a disclaimer: these descriptions are meant to give you a feel for how the studies set up their training programs; if you are new to strength training you should seek other resources (such as your friendly neighborhood sports PT) to design a safe, effective program appropriate for you as an individual. If you are new to strength training the good news is that your body will respond strongly to ANY small to moderate strength training stimulus, so aside from understanding safety guidelines program design shouldn’t be overly complicated.

                Heavy Resistance Training

- Load - Although maximal strength development benefits from >80% 1RM load these studies showed that more moderate loading 60-80%RM was sufficient to obtain the benefits to running.  

- Exercise Selection -  Every study used at least one multi-joint exercise including: squat, leg press, lunges, deadlifts, Romanian deadlifts, etc. Additionally, accessory isolation work was also used for the big muscle groups of the legs; calf strengthening was used in many studies due to its special role in running.

- Volume of Training – Per session start with 3-4 exercises (at least 2 multi-joint exercises) with 2-3 sets per exercise. Progress over the course of months to 4-6 exercises per session with 3-6 sets per exercise. Perform no greater than 15 sets per week for a given muscle group.

 

 

Plyometric Training

- Exercise Selection – The common exercises used were: counter movement jumps, squat jumps, single leg hops, broad jumps, and drop jumps (<36” box)

- Volume/Intensity of Training - start with 30 foot-contacts per session progressing to 60 contacts/session by the end of the second week. Progress gradually over the course of 9-12 weeks to 100-200 foot-contacts per session. Perform each exercise in sets of 4-10 reps with 2-3 minute breaks between sets.

                Combined Training

-   Perform a little under half of the volume of each program; start each session with    plyometrics and finish with strength training.

Why it Works

As previously mentioned strength training is well established in its ability to improve running economy, AKA running efficiency. The exact mechanism of this is not well understood however strength training is known to increase the stiffness of tendons (Bohm et al., 2015), and a stiffer tendon provides more “energy-free elastic recoil” or bounciness with each step. Other theories include improved neuromuscular efficiency (meaning the nerves become better at conducting signals), or that improved strength allows better form (for example, some runners have weak hips which causes sloppy/inefficient hip movements).

Final Thoughts

If your trying to improve your running performance the most important things you can do is have a well-designed running program, eat healthfully, and sleep enough. While there used to be some controversy, now the science is clear, one of the next steps you should take to improve running performance is incorporate strength training. Additionally, from my perspective as a physical therapist, strength training increases resilience to running injury. For example, 37% of all lower leg injuries in running are Achilles tendonitis cases (Taunton et al., 2003), and as previously mentioned strength training increases tendon resilience.  Even more convincingly Lauersen et al. (2017) found in their meta-analysis that strength training on average reduced sports-related overuse injuries by 50%!   Actually, EVERYBODY should perform some degree of strength training as it is promotes so many aspects of health and function, but that’s the topic for a whole different article…. Until then run fast and lift heavy!  

 

References

Balsalobre-Fernández, C., Santos-Concejero, J., & Grivas, G. V. (2016). Effects of Strength Training on Running Economy in Highly Trained Runners. Journal of Strength and Conditioning Research,30(8), 2361-2368. doi:10.1519/jsc.0000000000001316

Blagrove, R. C., Howatson, G., & Hayes, P. R. (2018). Effects of Strength Training on the Physiological Determinants of Middle- and Long-Distance Running Performance: A Systematic Review. Sports Medicine,48(5), 1117-1149. doi:10.1007/s40279-017-0835-7

Bohm S, Mersmann F, Arampatzis A. Human tendon adaptation in response to mechanical loading: a systematic review and meta-analysis of exercise intervention studies on healthy adults. Sports Med Open. 2015;1(1):7

Taunton, J. E. (2003). A prospective study of running injuries: The Vancouver Sun Run "In Training" clinics. British Journal of Sports Medicine,37(3), 239-244. doi:10.1136/bjsm.37.3.239