Gene expression changes in vastus lateralis muscle after different strength training regimes during rehabilitation following anterior cruciate ligament reconstruction

PLOS ONE, 2021 · DOI: https://doi.org/10.1371/journal.pone.0258635 · Published: October 14, 2021

Simple Explanation

This study explores how different types of strength training affect muscle recovery after ACL reconstruction (ACL-R). Specifically, it looks at gene expression changes in the vastus lateralis muscle following concentric/eccentric quadriceps strength training with (CON/ECC+) or without (CON/ECC) eccentric overload. The study found that CON/ECC+ induced a greater hypertrophy of the quadriceps muscle, but strength deficits persisted, and there was an unexpected increase in slow type I fibers. The research analyzes the mRNA levels of 84 marker genes in muscle biopsies to understand these changes. The results showed significant changes in the expression of 26 mRNAs, with different patterns between the two training methods for 16 mRNAs, suggesting an enhanced hypertrophic stimulus after CON/ECC+. The type of autograft used in ACL-R also influenced gene expression.

Study Duration

12 weeks

Participants

31 recreational athletes after ACL-R

Evidence Level

Not specified

Key Findings

1
Significant changes were detected in the expression of 26 mRNAs, several of them involved in muscle wasting/atrophy, indicating ongoing muscle remodeling processes.
2
Different patterns were observed for 16 mRNAs depending on the strength training mode, suggesting an enhanced hypertrophic stimulus or fast contractility after CON/ECC+.
3
The type of autograft (quadriceps vs. semitendinosus tendon) influenced gene expression, with lower expression of 6 mRNAs involved in skeletal muscle hypertrophy or contractility in the quadriceps autograft group.

Research Summary

This study investigated gene expression changes in the vastus lateralis muscle following different strength training regimes (CON/ECC+ and CON/ECC) during rehabilitation after ACL-R. The results indicated significant changes in the expression of 26 mRNAs, with different patterns observed between the two training modes, suggesting an enhanced hypertrophic stimulus and mechanical sensing after CON/ECC+. The type of autograft also influenced gene expression, and ongoing muscle wasting processes were evident. CON/ECC+ might lead to a faster muscle phenotype.

Practical Implications

Rehabilitation Strategies

The study suggests that CON/ECC+ training may offer a superior hypertrophic stimulus compared to CON/ECC during ACL-R rehabilitation, potentially leading to better muscle recovery.

Autograft Selection

The findings highlight the importance of considering the type of autograft used in ACL-R, as it can affect muscle regeneration and gene expression.

Muscle Quality Improvement

The study indicates ongoing muscle wasting processes during rehabilitation, suggesting the need for interventions to improve muscle quality alongside hypertrophy.

Study Limitations

1
The biopsies could not be obtained on exactly the same time-point after the last exercise bout in all subjects
2
The subjects´ activities of regular daily living probably also differed to some extent.
3
lack of a control group without training.

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