The Effect of Tibial Internal and External Rotation on Hamstring Activity and Knee Flexion Strength

• Age and Gender and Characteristics of Subjects:
  • Age
    • 20 Men - 24.5 (2.8 = standard deviation) years old; 20 Women - 23.7 (2.3) years old
      • total (40) - 24.1 (2.6) years old

  • BMI
    • Men - 24.8 (2.8); Women - 22.3 (2.4)
      • total - 23.5 (2.9)

• Characteristics:
  • Study Design:
    • Warm-up -
      • Subjects performed a 5-minute warmup on a stationary bicycle and isometric strength assessments of the knee flexors of the right lower limb with a dynamometer in a seated position

    • Electrode set-up -
      • Midway between the ischial tuberosity and medial epicondyle for the medial hamstrings, and midway between the ischial tuberosity and lateral epicondyle of the lateral hamstrings.

    • Seat set-up -
      • Pelvis and distal thigh secured to a dynamometer chair with straps, and the lower leg secured to the lever arm with a strap just proximal to the malleoli.
      • Axis of rotation aligned with the lateral femoral epicondyle, when the knee is positioned at 40° of flexion

    • Protocol - (order of knee flexor testing was randomized by a computer program)
      • Maximum isometric contraction values for the hamstrings were obtained in prone, with 25° of knee flexion and neutral tibial rotation
        • Used to standardize data obtained in data collection

      • Submaximal isometric testing with desired tibial rotation was performed to familiarize subjects with the protocol
      • Four 5-second maximal isometric knee flexor contractions were performed by each subject; 2 with maximum medial tibial rotation, and 2 with maximum lateral tibial rotation
        • The stronger of each of the two rotations were used for data analysis
        • All subjects were given standardized instructions during testing

      • Statistical Analyses
        • General linear model was used to identify differences in normalized muscle activation levels between the different hamstring compartments and tibial rotation, along with within-subjects factors and between-group factors (sex).
        • Independent student t-test used to compare men vs. women data
        • Alpha set for 0.05

• Inclusion Criteria: n/a
• Exclusion Criteria:
  • A history of knee surgery or any serious neuromusculoskeletal injury of the lower limb
  • Lesser injury (not leading to modification of activities) of the hamstring, gluteal, or back muscles in the 3 months prior to data collection
  • Knee pain during the 3 months prior to data collection
  • BMI > 35

• Knee flexor strength with medial rotation (MR) (in Newtons, N)
• Knee flexor strength with lateral rotation (LR) (in Newtons, N)
• Medial Hamstring (MH): Lateral Hamstring (LH) activation ratio with MR
• MH: LH activation ratio with LR

1 - significantly greater men vs. women (p < 0.01)

2 - significantly greater mean strength value when compared with same measure in LR (p < 0.01)

3 - Significantly greater value for MH: LH activation ratio with tibia in MR than in LR (p < 0.01)

ConclusionsTibial rotation influences MH and LH activation during knee flexion. Medial tibial rotation influenced biceps femoris activity and subsequent knee flexor strength more so than lateral tibial rotation. That is, biceps femoris activity was reduced as a result of medial tibial rotation, more than it was increased during tibial external rotation; however, the decrease in biceps femoris during medial tibial rotation also resulted in a decrease of knee flexor strength. This trend continued regardless of the sex of the subject, although force production was less in females than males.Conclusions of the ResearchersTibial rotation should be considered when designing an exercise regimen involving hamstring strengthening especially when considering rehabilitation needs of the patient/client.

Caption: The set-up for recording of knee flexor activity with differing tibial rotations - Jonasson et al., 2015

The set-up for recording of knee flexor activity with differing tibial rotations - Jonasson et al., 2015

Review & Commentary:

The authors used a simple experimental design to investigate the hypothesis of whether tibial rotation influences activity of the medial (semimembranosus and semitendinosus ) and lateral hamstrings (biceps femoris ). They used surface electromyography and a dynamometer to measure how tibial rotation affected medial and lateral hamstring contribution, as well as knee flexor strength. The authors also compared data between groups to reduce the likelihood of group differences influencing data. Although the study design was cross-sectional, the authors randomized the order of protocols for each subject.

The study also had limitations that must be considered before implementation into practice. First, the subject population was relatively homogenous, young (24.1), and healthy (23.5 average BMI) without any comorbidities, so it may not be possible to generalize results. Second, tibial rotation was not standardized across all subjects. This could lead to differences in activity that were influenced by a subjects range of motion. Third, neutral tibial rotation was not tested in an attempt to reduce the influence of fatigue; however, this leaves a critical data set unavailable for analysis. Fourth, isometric contractions were used for data analysis; dynamic contractions were not performed. Although inferences can be drawn about dynamic muscle actions, further study is warranted. Finally, the study was performed on individuals free of lower extremity pathology, so the results may not be applicable to injured populations.

Why is this study important?

The study provides evidence that medial tibial rotation decreases the contribution of biceps femoris in a maximum isometric knee flexion exercise at the expense of maximum force (91.7% of force relative to lateral rotation of the tibia). The semimembranosus and semitendinosus do not appear to be influenced by tibial rotation during knee flexion. Further, while force output was significantly greater in males, there were no statistically significant differences between sexes with respect to activation ratios.

How does it affect practice?

The current study provides support for consideration of tibial rotation during exercise due to its effect on biceps femoris activity. Specifically, tibial internal rotation reduces biceps femoris contribution while maintaining similar levels of activity of the semimembranosus and semitendinosus . Inferences can be made about tibial rotation's influence on biceps femoris activation during other exercises such as squatting , lunging , step-ups , etc; however, further research is needed.

How does it relate to Brookbush Institute Content?

The biceps femoris is cited as over-active in the predictive models of postural dysfunction proposed by the Brookbush Institute, specifically Lower Leg Dysfunction (LLD) , Lumbo-pelvic Hip Complex Dsyfunction (LPHCD) and Sacroiliac Joint Dysfunction (SIJD) . Over-activity of the tibial external rotators (biceps femoris ), may result in synergistic dominance and relative inhibition of the gluteus maximus , as well as, an increase in the valgus moment at the knee, resulting in sub-optimal movement patterns that may increase the risk of injury (1-3). Consideration of tibial rotation is essential to designing an optimal exercise program or rehab intervention for those exhibiting dysfunction of the lower half of the body. The Brookbush Institute does not specifically recommend exercises with the intent of strengthening the knee flexors; due to its propensity to increase the activity of the commonly over-active biceps femoris . If isolation exercise is to be performed, the Brookbush Institute recommends exercises that strengthen the commonly under-active muscles such as gluteus maximus and tibialis anterior . Although the current study does support the idea that isolated knee flexion exercises can be performed in seated position with medial tibial rotation to reduce the contribution of biceps femoris , the Brookbush Institute recommends release and lengthening of the tibial external rotators , activation of the tibial internal rotators , and careful consideration of foot position and relative tibial rotation during integrated movement patterns.

A similar methodology was used in a this study - Bell, D. R., Oates, D. C., Clark, M. A., & Padua, D. A. (2013). Two-and 3-dimensional knee valgus are reduced after an exercise intervention in young adults with demonstrable valgus during squatting. Journal of athletic training,48(4), 442-449.

The videos below are all related to common strategies employed by the Brookbush Institute to address biceps femoris over-activity and tibial internal rotator under-activity.

Brookbush Institute Videos

Biceps Femoris Static SA Release

Biceps Femoris SA Active Release

Biceps Femoris Active Stretch

Dynamic Biceps Femoris Stretch

Tibial Internal Rotator Activation

Quick Tibialis Anterior and Tibial Internal Rotator Activation

Tibial Internal Rotator Facilitation Taping

References:

1. Hewett, T. E., Myer, G. D., Ford, K. R., Heidt, R. S., Colosimo, A. J., McLean, S. G., & Succop, P. (2005). Biomechanical measures of neuromuscular control and valgus loading of the knee predict anterior cruciate ligament injury risk in female athletes A prospective study. The American journal of sports medicine, 33(4), 492-501.
2. Lewis CL, Sahrmann. 2005 Timing of muscle activation during prone hip extension. Abstract. J Orhop Sports Phys Ther 35(1): A56.
3. Tateuchi, H., Taniguchi, M., Mori, N., Ichihashi, N. Balance of hip and trunk muscle activity is associated with increased anterior pelvic tilt during prone hip extension (2013) Journal of Electromyography and Kinesiology 22 (3). 391-397

© 2016 Brent Brookbush

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