Publications
Effects of keiser-assisted Nordic hamstring curl training on hamstring flexibility, mechanical properties, and pitching performance in high school baseball pitchers
Authors: Ye-Jun Han 1, Hyun Ahn 2, Sea-Hyun Bae 3, Kyung-Yoon Kim 3
Affiliations:
- Department of Physical Therapy, Samsung Electronic Musculoskeletal Disorders Prevention Center, Gwangju, Republic of Korea
- Social Healing Team, National Trauma Recovery Center, Gwangju, Republic of Korea
- Department of Physical Therapy, Dongshin University, Naju, Republic of Korea
Journal: Physical Activity and Nutrition - September 2026, Volume 30, Issue 3, Pages 41-47 (DOI: 10.20463/pan.2026.0038)
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Field & Applications:
- Sport
- Muscle development / Performance
Myoton Clarification Note: A Guide to Interpreting the Inverse Relationship Between Logarithmic Decrement and Tissue Elasticity
Purpose: This study aimed to investigate the effects of 10-week Keiser-assisted Nordic hamstring curl (NHC) training on the mechanical properties, muscle strength, and flexibility of the hamstrings, as well as shoulder range of motion (ROM) and pitching performance in high school baseball pitchers.
Methods: Sixteen high school baseball pitchers performed Keiser assisted NHC training for 10 weeks. The pre- and post-training measurements included the mechanical properties of the hamstrings (muscle tone, stiffness, elasticity, creep) measured using MyotonPRO, isometric muscle strength, trunk and shoulder ROM, and pitching performance (velocity and spin rate).
Results: After training, hamstring muscle tone, stiffness, and elasticity significantly decreased (p < 0.01), whereas creep and isometric strength significantly improved (p < 0 0.001) (effect size dz = 0.84-2.90). Additionally, the trunk flexion range significantly increased (p < 0.001, dz = 2.12), and the glenohumeral internal rotation deficit in the throwing shoulder significantly improved (p < 0.05). The pitching velocity (p < 0.001, dz = 2.61) and spin rate (p < 0.01, dz = 0.89) significantly increased.
Conclusion: Keiser-assisted NHC training improved hamstring mechanical efficiency, isometric strength, and trunk flexibility, with concurrent gains in pitching velocity and spin rate. As this was a single-group pre-post study without a control group, these findings require confirmation through controlled trials.
Keywords: Nordic hamstring curl, hamstring flexibility, mechanical properties, pitching performance, injury prevention, baseball pitchers