TY - JOUR
T1 - Chronic Sequelae After Muscle Strain Injuries
T2 - Influence of Heavy Resistance Training on Functional and Structural Characteristics in a Randomized Controlled Trial
AU - Bayer, Monika L.
AU - Hoegberget-Kalisz, Maren
AU - Svensson, Rene B.
AU - Hjortshoej, Mikkel H.
AU - Olesen, Jens L.
AU - Nybing, Janus D.
AU - Boesen, Mikael
AU - Magnusson, S. Peter
AU - Kjaer, Michael
N1 - Publisher Copyright:
© 2021 The Author(s).
PY - 2021
Y1 - 2021
N2 - Background: Muscle strain injury leads to a high risk of recurrent injury in sports and can cause long-term symptoms such as weakness and pain. Scar tissue formation after strain injuries has been described, yet what ultrastructural changes might occur in the chronic phase of this injury have not. It is also unknown if persistent symptoms and morphological abnormalities of the tissue can be mitigated by strength training. Purpose: To investigate if heavy resistance training improves symptoms and structural abnormalities after strain injuries. Study Design: Randomized controlled trial; Level of evidence, 1. Methods: A total of 30 participants with long-term weakness and/or pain after a strain injury of the thigh or calf muscles were randomized to eccentric heavy resistance training of the injured region or control exercises of the back and abdominal muscle. Isokinetic (hamstring) or isometric (calf) muscle strength was determined, muscle cross-sectional area measured, and pain and function evaluated. Scar tissue ultrastructure was determined from biopsy specimens taken from the injured area before and after the training intervention. Results: Heavy resistance training over 3 months improved pain and function, normalized muscle strength deficits, and increased muscle cross-sectional area in the previously injured region. No systematic effect of training was found upon pathologic infiltration of fat and blood vessels into the previously injured area. Control exercises had no effect on strength, cross-sectional area, or scar tissue but a positive effect on patient-related outcome measures, such as pain and functional scores. Conclusion: Short-term strength training can improve sequelae symptoms and optimize muscle function even many years after a strain injury, but it does not seem to influence the overall structural abnormalities of the area with scar tissue. Registration: NCT02152098 (ClinicalTrials.gov identifier).
AB - Background: Muscle strain injury leads to a high risk of recurrent injury in sports and can cause long-term symptoms such as weakness and pain. Scar tissue formation after strain injuries has been described, yet what ultrastructural changes might occur in the chronic phase of this injury have not. It is also unknown if persistent symptoms and morphological abnormalities of the tissue can be mitigated by strength training. Purpose: To investigate if heavy resistance training improves symptoms and structural abnormalities after strain injuries. Study Design: Randomized controlled trial; Level of evidence, 1. Methods: A total of 30 participants with long-term weakness and/or pain after a strain injury of the thigh or calf muscles were randomized to eccentric heavy resistance training of the injured region or control exercises of the back and abdominal muscle. Isokinetic (hamstring) or isometric (calf) muscle strength was determined, muscle cross-sectional area measured, and pain and function evaluated. Scar tissue ultrastructure was determined from biopsy specimens taken from the injured area before and after the training intervention. Results: Heavy resistance training over 3 months improved pain and function, normalized muscle strength deficits, and increased muscle cross-sectional area in the previously injured region. No systematic effect of training was found upon pathologic infiltration of fat and blood vessels into the previously injured area. Control exercises had no effect on strength, cross-sectional area, or scar tissue but a positive effect on patient-related outcome measures, such as pain and functional scores. Conclusion: Short-term strength training can improve sequelae symptoms and optimize muscle function even many years after a strain injury, but it does not seem to influence the overall structural abnormalities of the area with scar tissue. Registration: NCT02152098 (ClinicalTrials.gov identifier).
KW - chronic muscle injury
KW - fatty infiltration
KW - heavy resistance training
KW - scar tissue
U2 - 10.1177/03635465211026623
DO - 10.1177/03635465211026623
M3 - Journal article
C2 - 34264782
AN - SCOPUS:85110102514
VL - 49
SP - 2783
EP - 2794
JO - American Journal of Sports Medicine
JF - American Journal of Sports Medicine
SN - 0363-5465
IS - 10
ER -