Muscle fibers run in random directions within each muscle, originating and ending at various points. Despite what many think, muscles and muscle fibers don’t run from the beginning to the end of a muscle. Therefore, exercises routines must stress all the varying muscle fiber orientation for the best workout.

 

The hamstrings muscles are split into three muscles: 
  1. Semimembranosus
  2. Semitendinosus
  3. Biceps Femoris
Excellent, we know muscle fibers lie erratically, we know the hamstrings contain three muscles, but what exercises target the full muscular spectrum? How can sports team, personal trainers, and physical therapist apply this information?

 

 

Schoenfeld (2014) had ten young experienced resistance trained men were recruited to participate in the study. Each subject performed both the stiff-leg deadlift and the leg curl. 
Testing took place over two sessions. In the first session we tested subject’s maximal ability to perform 8 repetitions (8RM) on both exercises. The second session involved assessing activation during performance of the movements at the subject’s 8RM.

 

Surface electromyography (EMG) determined the muscle activation. Electrodes were placed on the upper and lower aspects of the subject’s medial and lateral hamstrings. All 8RM sets were performed to failure.

What Exercise Increases Hamstrings Activity?

 

In both exercises, activation of the upper hamstrings was similar. For the lower medial and lateral hamstrings, there was significant activation during the lying leg curl (~170% greater for the lateral hamstrings and ~65% for the stiff-leg deadlift). 
One expects greater activation of the lateral hamstrings during the leg curl, as the short head of the biceps femoris doesn’t cross the hip joint. The medial hamstrings results were surprising, as the medial muscles cross both the hip and knee. 

 

Practical Hamstrings Muscles Training

Overall, performing a hip- and knee-dominant hamstrings exercise is important for maximizing muscular activation of the hamstrings. However, if time is limited or someone is specifically looking for hamstrings. For example, if a physical therapist is working with a patient demonstrating weak medial hamstrings, the lying leg-curl maximally elicits this muscle. If seeking complete hypertrophy of the hamstrings, a personal trainer can apply a variety of knee- and hip-dominant movements are important for maximizing muscular activation which correlates with hypertrophy.

 

References:
  1. Schoenfeld BJ, Contreras B, Tiryaki-Sonmez G, Wilson JM, Kolber MJ, Peterson MD. Regional Differences in Muscle Activation During Hamstrings Exercise.J Strength Cond Res. 2014 Jun 24. [Epub ahead of print]
Written by Dr. John Mullen, DPT, CSCS