June 2023

Hamstring Muscle Stiffness Affects Lower Extremity Muscle Recruitment and Landing Forces during Double-Legs Vertical Jump

Authors: Amornthep Jankaew 1, Yih-Kuen Jan 2, Ing-Shiou Hwang 1, 3, Li-Chieh Kuo 1, 4, 5, Cheng-Feng Lin 1, 3, 6


  1. Institute of Allied Health Sciences, College of Medicine, National Cheng Kung University, Tainan, Taiwan
  2. Department of Kinesiology and Community Health, College of Applied Health Sciences, University of Illinois at Urbana-Champaign, Champaign, IL, USA
  3. Department of Physical Therapy, College of Medicine, National Cheng Kung University, Tainan, Taiwan
  4. Department of Occupational Therapy, College of Medicine, National Cheng Kung University, Tainan, Taiwan
  5. Medical Device Innovation Center, National Cheng Kung University, Tainan, Taiwan
  6. Physical Therapy Center, National Cheng Kung University Hospital, Tainan, Taiwan

Journal: Sports Biomechanics - June 2023 (DOI: 10.1080/14763141.2023.2219670)

It is unclear how hamstring stiffness influences lower limb muscle activation during jump-landing mechanics. The study aimed to investigate the role of the hamstring stiffness on lower limb muscle recruitment during jumping manoeuvres.

Thirty male athletes were recruited and allocated into high- and low-stiffness groups. Hamstring stiffness was determined as the average stiffness of bilateral hamstrings using a MyotonPRO. Surface electromyography of the bilateral gluteus maximus, quadriceps, and hamstring muscles was assessed during the takeoff, at ground contact, and at landing, while ground reaction force (GRF) was measured during the squat jump, countermovement jump, and drop vertical jump.

The results showed that athletes with greater hamstring stiffness exhibited a higher median frequency of the lateral hamstrings in both limbs and the vastus medialis in the dominant limb than the low-stiffness group during takeoff, adjustment, and landing phases for all vertical jumps. The high stiffness group landed with lower vertical GRF in the drop vertical jump.

In conclusion, athletes with high hamstring stiffness showed greater motor unit recruitment during takeoff and landing phases. This recruitment did not influence takeoff performance but aid with absorbing landing force. Therefore, the contribution of the lower limb muscle stiffness should be considered in sports activities.


Keywords: hamstring stiffness, hamstring recruitments, median frequency, jumping mechanics

The current study compared the muscle recruitment of the lower limb and jumping mechanics among athletes with high and low stiffness of the hamstrings. Athletes with similar hamstring strength but higher levels of hamstring muscle stiffness displayed greater bilateral recruitment of the gluteus maximus, quadriceps, and hamstrings during the standing vertical jumps compared to the low hamstring stiffness group. Although the greater recruitment did not affect takeoff performance, individuals with higher hamstring muscle stiffness were able to land with a lower vertical ground reaction force. The findings demonstrate the importance of muscle stiffness assessment to modulate the activation levels that play a significant role in mitigating the risk of lower limb injuries during jump-landing activities.