Medial and Lateral Heel Whips: Prevalence and Characteristics in Recreational Runners

256 participants (512 feet analyzed)

Demographics

• 138 females
  • Age (y): 41.9 ± 9.7 (range 20-65)
  • Body mass index (kg/m²): 22.2 ± 2.9 (range 17.9-36.8)

• 118 males
  • Age (y): 42.3 ± 10.9 (range 17-80)
  • Body mass index (kg/m²): 23.6 ± 2.3 (range 18.8-32.5)

• Participants were recruited from the RunSafe program at the University of California, San Francisco (a pay-for-service wellness facility). Running performance/experience varied greatly between participants.

Inclusion Criteria:

• N/A

Exclusion Criteria:

• N/A

• Participants performed a 2-minute warmup on the treadmill, then increased their speed to running at a self-selected comfortable pace.
• A 60 second video was recorded from a video camera positioned 11 feet posterior to the treadmill.
• Heel whip angle was measured as the initial angle of the under surface of the shoe, relative to a vertical line just prior to toe-off in late stance.
• Next, the frame with the maximum amount of deviation was recorded, and the angle of the plantar surface of the shoe to a vertical line was recorded.
• Heel whip was calculated at the angle just before toe-off subtracted from the angle of maximum deviation.
  • a positive number indicated a medial heel whip
  • a negative number indicated a lateral heel whip

• This procedure was repeated on 3 consecutive strides and averaged for analysis.
• 29 subjects (58 feet) were measured a second time to determine the reliability of this measurement method.
• Mean and standard deviation heel whips were calculated for the entire group. An arbitrary cut-off of ±5 degrees was selected as criteria for normal heel deviation.
  • Heel whip 5-10° = W_5-10
  • Heel whip > 10° = W_10+

• Secondary analysis was performed to determine a relationship between body mass index (BMI) and heel whips.
  • Underweight subjects (BMI < 20)
  • Normal-weight subjects (BMI 20-25)
  • Overweight subjects (BMI > 25)

• Adjusted t-tests were performed to evaluate differences across 3 BMI groups.
• Pearson's correlations were performed to determine relationships between BMI and average heel whip.
• Intra-rater reliability was evaluated using intra-class correlation coefficients (ICC).

ResultsPrevalence:

• Overall mean whip angle across all subjects was 0.4 (medial) ± 9.2°.
• Of the 512 feet analyzed, 274 (54%) had a 5° whip or greater.
• Whip severity was stratified as :
  • 87/512 (17%) W_10+ medial
  • 49/512 (10%) W_5-10 medial
  • 40/512 (8%) W_10+ lateral
  • 98/512 (19%) W_5-10 lateral

Characteristics:

• Participants with a W_5-10 medial heel whip were similar in age and BMI (41.2 ± 9.3 years, 23.0 ± 4.4 kg/m²) compared to subjects with a W_5-10 lateral heel whip (42.3 ± 9.6 years, 22.4 ± 2.5 kg/m²).
• Those with W_10+ medial whip were significantly older (44.2 vs. 38.6 years) and had a greater BMI (24.0 vs. 21.8 kg/m²) compared to subjects with W_10+ lateral whip.

BMI Evaluation:

• Overweight participants had a significantly greater medial heel whip compared with both the underweight and normal weight subjects (P < 0.008).
  • Weak but significant relationship between BMI and average heel whip angle medially (r = 0.25; P < 0.001)

Gender Evaluation:

• No significance was found in predicting gender based on heel whip angle.

Reliability:

• Measurement showed excellent reliability across all measures (ICC = 0.994; standard error of the mean = 1.2°).
• Within measures of medial and lateral heel whips had excellent reliability (ICC = 0.960 and 0.953 respectively for medial and lateral whips).

Our Conclusions

Researchers' Conclusions

More than half of the recreational runners had medial or lateral heel whip of greater than 5°. Overweight runners had more medially directed whips compared with normal and underweight runners.

Caption: Picture of Marathon Runners

Marathon Runners. Image: https://commons.wikimedia.org/w/index.php?curid=1420320

Review and Commentary:

To our knowledge this is the first study to investigate the prevalence and characteristics of heel whip in recreational runners. This study provides a new method for quantifying heel whip during running using standard videotaping technology.

Strengths and Weaknesses

The study had many methodological strengths, including:

• This was the first study to describe the prevalence and characteristics of the heel whip in recreational runners.
• The study validated the reliability of standard videotaping technology to accurately identify and quantify heel whip in runners.
• A large sample size was used in this study - 256 runners (518 feet analyzed).

Weaknesses that should be noted prior to clinical integration of the findings include:

• Participants were recruited from a pay-for-service wellness facility catering to runners with the financial means to afford the service. This may result in decreased generalizability, and care should be taken applying these findings to other populations.
• Inclusion or exclusion criteria were not provided. This could result in skewed data due to unknown injuries or changes to running mechanics.
• The measurement techniques used 2D technology for a transverse plane movement, which may result in a less accurate measurement of heel whip, which is a multiplanar motion.
• No standardization of footwear was enforced, resulting in participants wearing a variety of shoe brands and running with varied shoe support. How this may affect the measurement of heel whip is unknown.

How This Study is Important:

This study is the first to provide reliable information about the characteristics and prevalence of heel whips in recreational runners. The root cause(s) and clinical significance of this deviation are unknown. The authors speculate that because heel whip is a transverse plane motion, the cause may be related to tibial and/or femoral rotation (4-6). It may also be the result of a variable described as the free vertical moment (7-8). This variable is defined as a torque around a vertical axis, which may be the result of friction between the foot and the ground (7). The potential energy stored by the runner during the stance phase is released when the foot is taken off the ground during the initial swing phase resulting in the observed medial or lateral deviation of the heel. More research investigating causes of heel whip and correlation with injury are needed.

How the Findings Apply to Practice:

The findings of this study suggest that heel whip may increase with age and BMI. Further, heel whip may be reliably assessed using standard video equipment. Human movement professionals should consider identifying heel whip as part of a comprehensive movement assessment, and/or an assessment of running mechanics.

How does it relate to Brookbush Institute Content?

The Brookbush Institute's (BI) predictive model of lower extremity dysfunction (LED)  suggests that "heel whip" may be related to feet turn-out ; a common sign observed during an overhead squat assessment . Studies demonstrate that feet turn-out  may be associated with a positive Ober's Test and knee pain, as well as correlated with a functional valgus and knee osteoarthritis (9-12).

Although the clinical significance of heel whip has yet to be investigated, this study takes the first step toward documenting the distribution of heel whip in recreational runners and determining the reliability of assessment of heel whip using standard video technology. Human movement professionals who work with runners may consider the assessment of heel whip in conjunction with the interventions implied by the LED  model. Below are a few videos that may be related to the assessment and correction of heel whip:

Overhead Squat Assessment 5 - Feet Turn Out Breakdown

Ober's Test (Tensor Fascia Latae Flexibility Assessment)

Hip Flexion/Knee Extension Goniometry (Bicep's Femoris Length)

Tensor Fascia Latae Self-administered Release

Tensor Fasciae Latae Manual Static Release

Biceps Femoris Self-administered Dynamic Release

Biceps Femoris Self-administered Manual Release

Bibliography:

1. Daoud, A. I., Geissler, G. J., Wang, F., Saretsky, J., Daoud, Y. A., & Lieberman, D. E. (2012). Foot strike and injury rates in endurance runners: a retrospective study. Med Sci Sports Exerc, 44(7), 1325-1334.
2. van Gent, B. R., Siem, D. D., van Middelkoop, M., van Os, T. A., Bierma-Zeinstra, S. S., & Koes, B. B. (2007). Incidence and determinants of lower extremity running injuries in long distance runners: a systematic review. British journal of sports medicine.
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4. Powers, C. M., Chen, P. Y., Reischl, S. F., & Perry, J. (2002). Comparison of foot pronation and lower extremity rotation in persons with and without patellofemoral pain. Foot & ankle international, 23(7), 634-640.
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6. Reischl, S. F., Powers, C. M., Rao, S., & Perry, J. (1999). Relationship between foot pronation and rotation of the tibia and femur during walking. Foot & ankle international, 20(8), 513-520.
7. Holden, J. P., & Cavanagh, P. R. (1991). The free moment of ground reaction in distance running and its changes with pronation. Journal of biomechanics, 24(10), 887891-889897.
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9. Andrews, M., Noyes, F. R., Hewett, T. E., & Andriacchi, T. P. (1996). Lower limb alignment and foot angle are related to stance phase knee adduction in normal subjects: a critical analysis of the reliability of gait analysis data. Journal of orthopaedic research, 14(2), 289-295.
10. Barrios, J. A., Crossley, K. M., & Davis, I. S. (2010). Gait retraining to reduce the knee adduction moment through real-time visual feedback of dynamic knee alignment. Journal of biomechanics, 43(11), 2208-2213.
11. Winslow, J., & Yoder, E. (1995). Patellofemoral pain in female ballet dancers: correlation with iliotibial band tightness and tibial external rotation. Journal of Orthopaedic & Sports Physical Therapy, 22(1), 18-21.
12. Andrews, M., Noyes, F. R., Hewett, T. E., & Andriacchi, T. P. (1996). Lower limb alignment and foot angle are related to stance phase knee adduction in normal subjects: a critical analysis of the reliability of gait analysis data. Journal of orthopaedic research, 14(2), 289-295.

© 2017 Brent Brookbush

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