KNEE SIG NEWSLETTERJULY 2020
July Newsletter Topic: Regaining Quadriceps Strength Early after ACL Reconstruction (Part 2 of 2)Courtesy of SIG Education Committee Members Grant Poston and Joseph Hannon Developing strength following an ACL Reconstruction can be quite challenging due to multiple factors including quadriceps atrophy, atherogenic muscle inhibition, and anterior knee pain. Incorporating blood flow restriction early on in rehab may help prevent atrophy and enhance strength and hypertrophy
while heavy loading is contraindicated or unable to be achieved due to pain. When a patient is appropriate for higher loading activities, developing an appropriately loaded exercise program is the key to regaining quadriceps strength. The following information regarding the basic principles of strength
and conditioning, blood flow restriction, and exercise parameters to maximize strength and hypertrophy should all be considered when addressing post-operative quadriceps strength, Basic Principles of Strength and Conditioning - In order to increase a muscle’s ability to produce force (i.e. strength), both
mechanical and metabolic stimuli are needed
- According to Henneman’s Size Principle: lower-order motor units will be recruited first, while larger higher-order motor units are recruited when a sufficient stimulus is provided (i.e. higher loads) 2
- Higher-order motor units control a greater number of
muscle fibers and are often type-II (anaerobic) 1
- Exposing sufficient mechanical stress to a muscle creates mechanical deformation of the involved tissue and promotes adaptive structural, neural, and endocrine changes to increase muscle size and its ability to produce force 1,3
- Heavy resistance training
also involves the stimulation of various metabolic pathways and byproducts such as HGH, IGF-1, and MTORC1 4,5,6
- National Strength and Conditioning Association resistance guidelines:
*American College of Sports Medicine: 60-70% 1RM, 8-12 reps for beginners; 80-100% 1RM for advanced 1,3
Blood Flow Restriction - A modality that can be used to augment traditional rehabilitation following a knee injury and surgery
- Simulates a high loading environment through increased metabolic stress by creating a local hypoxic stimulus which results in greater metabolite accumulation 7,8
- Theoretically, this modality is useful early on in rehabilitation when high loads are either contraindicated or result in increased pain 7,8,9
- Additionally, in the context of traditional clinic-based rehabilitation, BFR may be useful when heavy resistance training equipment is not available
- Low-intensity resistance training with BFR can result in greater strength and muscle hypertrophy when compared to resistance training with the same intensity under normal flow and comparable to gains with moderate to high-intensity resistance training
7
- In post-op rehab from ACLR, performing the leg press 2x/week for 8 weeks at 30% 1RM with BFR compared to 70% 1RM resulted in similar improvements in strength and hypertrophy, but with greater ROM, less pain and swelling, and greater self-reported function 8
- Clinical Pearls:
- Properly screen patient for contraindications and precautions 12
- May consider speaking with referring provider
- Over educate patient and caregiver on the modality, the mechanism, the rationale for use, and the expected outcome
- The amount of occlusion used is typically based on a percentage of limb occlusion pressure (LOP). There are varied ways to obtain the “correct” pressure. Refer to the specific device's instructions.
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Strength Training Parameter Considerations - Minimal Effective Dose 13
- Minimum effective training dose required to increase 1-repetition maximum (1RM) strength in the squat and bench press appears to be a single set of 6–12 repetitions performed with high intensity (70-85% 1 RM) of effort at a training frequency of 2–3 times per week.
- Clinical Takeaway: When patients can tolerate high-intensity exercise, training heavy at least 2-3 times/week can elicit strength improvements.
- Training Volume vs. Training Frequency 14
- A systematic review and meta-analysis of 22 studies
- Significant effect of resistance training
frequency à higher training frequencies are translated into greater muscular strength gains
- The effects are primarily driven by training volume
- When volume was controlled for, there was no significant effect of
training frequency on muscular strength gains.
- Clinical Takeaways:
- Greater training frequencies can be used to increase overall training volume, which is then likely to result in
greater muscular strength gains.
- It remains unclear whether training frequency on its own has significant effects on strength gains.
- Training to Muscular Failure 15, 16
- When training to muscular failure, both high-load (>60% 1RM) and low-load (<60% 1RM) training induce muscular hypertrophy15
- Strength improvements are greater with high-load training
- With volume equated, exercising with low-loads (30% 1RM) developed strength similarly regardless of achieving muscular failure, but to a much lesser extent than high-load training (80% 1RM)16
- There were no differences in strength gains with high-load training with or without training to muscular failure
- Hypertrophy occurs similarly with high-load training to failure, high-load training without failure, and low-load training to failure
- Clinical Takeaways:
- Hypertrophy occurs with both low- and high-load training but may require muscular failure when training if training with low loads
- Significant strength improvements likely require high-load training, but may not require muscular failure
References: - Essentials of strength and conditioning. Fourth Edition. Haff G and Triplett T, editors. 2016. National Strength and Conditioning Association. Human Kinetics, Champaign, IL.
- Mendell L. The size principle: a rule describing the recruitment of motoneurons. J Neurophysiol. 2005; 93: 3024-3026.
- Ratamess N et al. Progression models in resistance training for healthy adults. Medicine and Science in Sports & Exercise. 2009;41(3): 687-708. SPECIAL COMMUNICATIONS: Position Stand.
- Gundermann DM, Walker DK, Reidy PT, Borack MS, Dickinson JM, Volpi E, Rasmussen BB. Activation of mTORC1 signaling and protein synthesis in human muscle following blood flow restriction exercise is inhibited by rapamycin. Am J Physiol Endocrinol Metab. 2014;306(10), E1198-1204.
- Takarada Y, Nakamura Y, Aruga S, Onda T, Miyazaki S, Ishii N. Rapid increase in plasma growth hormone after low-intensity resistance exercise with vascular occlusion. J Appl Physiol (1985). 2000;88:61-65.
- Nielsen JL, Aagaard P, Bech RD, Nygaard T, Hvid LG, Wernbom M, Frandsen U. Proliferation of myogenic stem cells in human skeletal muscle in response to low-load resistance training with blood flow restriction. J Physiol. 2012;590(Pt 17), 4351-4361. 773–782.
- Hughes L, Paton B, Rosenblatt B, et al. Blood flow restriction training in clinical musculoskeletal rehabilitation: a systematic review and
meta-analysis British Journal of Sports Medicine 2017;51:1003-1011.
- Hughes L, Patterson SD, Haddad F, et al. Examination of the comfort and pain experienced with blood flow restriction training during post-surgery rehabilitation of anterior cruciate ligament reconstruction patients: A UK National Health Service trial. Phys Ther Sport. 2019;39:90-98.
- Centner, C., Wiegel, P., Gollhofer, A., & König, D. (2019). Effects of blood flow restriction training on muscular strength and hypertrophy in older individuals: a systematic review and meta-analysis. Sports Medicine, 49(1), 95-108.
- Buckthorpe, M., La Rosa, G., & Della Villa, F. (2019). Restoring knee extensor strength after anterior cruciate ligament reconstruction: a clinical commentary. International journal of sports physical therapy, 14(1), 159.
- Patterson S, Hughes L, Warmington S, Burr J, Scott, B, Owens J, Abe T, Nielsen J, Libardi C, Laurentino G, Neto G, Brandner C, Martin-Hernandez J, Loenneke J. Blood flow restriction exercise: considerations of methodology, application and safety. Front Physiol. 2019; 5(10): Article 533.
- Whiteley, R. (2019). Blood Flow Restriction Training in Rehabilitation: A Useful Adjunct or Lucy's Latest Trick?. journal of orthopaedic & sports physical
therapy, 49(5), 294-298.
- Andruoulakis-Korakakis P, Fisher J, Steele J. The minimum effective training dose required to increase 1RM strength in resistance-trained men: a systematic review and meta-analysis. Sports Med. 2020; 50(4): 751-765.
- Grgic J et al. Effect of resistance training frequency on gains in muscular strength: a systematic review and meta analysis.
Sports Med. 2018; 48(5): 1207-1220.
- Schoefeld B, Grgic J, Ogborn D, Krieger J. Strength and hypertrophy adaptations between low- vs. high-load resistance training: a systematic review and meta-analysis. J Strength Cond Res. 2017; 31(12): 3508-3523.
- Lasevicius T et al. Muscle failure promotes greater muscle hypertrophy in low-load but not high-load resistance training.
J Strength Cond Res. 2019; 27.
McEwen, J.A., Owens, J.G. & Jeyasurya, J. Why is it Crucial to Use Personalized Occlusion Pressures in Blood Flow Restriction (BFR) Rehabilitation?. J. Med. Biol. Eng. 39, 173–177 (2019). https://doi.org/10.1007/s40846-018-0397-7
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