Article - Kalea, Eryn, Nisarg

EFFECTS OF UNILATERAL ECCENTRIC VERSUS CONCENTRIC TRAINING OF NON-IMMOBILIZED ARM DURING IMMOBILIZATION

Authors

  • Trevor C. Chen

  • Shang-Hen Wu

  • Hsin-Lian Chen

  • Wei-Chin Tseng

  • Kuo-Wei Tseng

  • Hsing-Yu Kang

  • Kazunori Nosaka

Presentation By

  • Kalea, Nisarg, and Eryn

PURPOSE

  • To compare the effects of:

    • Eccentric Training (ET) vs Concentric Training (CT) on:

      • Muscle function and cross-sectional area (CSA) of the immobilized arm.

      • Post-immobilization eccentric exercise muscle damage in the immobilized arm.

INTRODUCTION & BACKGROUND INFORMATION

  • Muscle disuse leads to:

    • Decreases in muscle mass

    • Reduction in force-generating capacity

CROSS-EDUCATION EFFECT

  • Neural Pathways: Mediates cross-education of motor function (Ruddy & Carson, 2013).

  • Magnitude of Increased Muscle Strength: 20.9% to 49.3% of ipsilateral strength gains (Munn et al., 2004).

  • Eccentric training may yield greater cross-education effects compared to concentric training (Green & Gabriel, 2018).

COMPARATIVE STUDIES

  • Valdes et al. (2021): 4-week immobilization study findings:

    • Control group: 22% decrease in MVCiso torque (no training).

    • CON-ECC: No change in MVCiso torque.

    • ECC-only group: 12% increase in MVCiso torque.

  • Tseng et al. (2020): Investigated contralateral effects by unilateral eccentric vs concentric resistance training.

  • Chen et al. (2018): Resistance training of the non-immobilized arm reduces muscle damage in the immobilized arm when eccentric exercise is performed post-immobilization (Contralateral Repeated Bout Effect).

INDICATORS OF MUSCLE DAMAGE

  • Indirect Markers:

    • MVCiso Torque

    • Range of Motion (ROM)

    • Upper Arm Circumference (CIR)

    • Muscle Soreness (DOMS)

    • Plasma Creatine Kinase (CK) (Hody et al., 2019)

HYPOTHESIS

  • ET will attenuate decreases in muscle function and CSA of the immobilized arm more than CT.

  • ET provides greater protection against muscle damage induced by maximal eccentric exercise performed after immobilization than CT.

METHODS

Participants

  • 36 Healthy Male Participants:

    • Sedentary

    • No previous musculoskeletal injuries

Immobilization

  • Non-dominant arm

  • Forearm cast and sling

Training

  • Non-immobilized training for 3 weeks, 2x per week:

    • 5 sets of 6 Eccentric/Concentric contractions.

    • Weight determined by MVCIso.

    • Load progression: 20%, 40%, 40%, 60%, 60%, 80%.

    • 3 days of rest between sessions.

Baseline Measurements

  • MVCiso and MVCcon

  • RMS of EMG

  • MCSA

  • Upper arm circumference

  • Muscle Hardness

  • Repeated Post-Immobilization Measures include:

    • MVCiso

    • Muscle Soreness

    • CK levels

RESULTS

Non-Immobilized Arm

  • Control Group: No significant changes in muscle metrics.

  • Eccentric Training (ET):

    • MVCiso torque: Increased by 17% (greater than CT's 6%).

    • CSA: Increased by 9% (CT: 3%).

    • Muscle Activation (RMS): Increased by 24% (CT: 9%).

    • Decreased muscle hardness/stiffness (P = 0.001).

  • Concentric Training (CT): Moderate gains, less than ET.

Immobilized Arm

  • Control Group: Significant reductions in strength (-17%) and muscle mass (-12%).

  • Eccentric Training (ET): Displayed an increase in muscle strength (MVCiso) and minimal losses in CSA (0%).

  • Concentric Training (CT): Moderate declines in strength (-4%) and CSA (-1.3%).

DISCUSSION

  • Support for Hypotheses:

    • ET effectively mitigates decreases in muscle function and CSA of the immobilized arm more than CT.

    • ET offers greater protection against muscle damage.

  • Muscle Damage Assessment:

    • MVCiso measured reductions only immediately post-training.

    • Minimal observed muscle soreness.

    • Concentric training resulted in noticeable muscle damage at higher intensities.

LIMITATIONS

  • Limited demographic: participants were only sedentary young men.

  • Small sample size: correlation needs larger studies for confirmation.

  • Possible gaps in EMG data collection and normalization.

PRACTICAL SIGNIFICANCE

  • Eccentric training is more beneficial than concentric training of the non-immobilized limb to minimize the adverse effects of immobilization.

  • Recommended as recovery/prevention strategies for those facing muscle disuse or immobilization.

FUTURE RESEARCH DIRECTIONS

  • Explore effects on other muscle groups and populations.

  • Investigate mechanisms further.

REFERENCES

  • Chen, T. C., et al. (2018)

  • Green, L. A., & Gabriel, D. A. (2018)

  • Hody, S., et al. (2019)

  • Ruddy, K. L., & Carson, R. G. (2013)

  • Tseng, W.-C., et al. (2020)

  • Valdes, O., et al. (2021)