The effect of repeated shocks on the low back during horse riding.

Overview

• This study investigates how repeated shocks experienced during horse riding impact the low back, focusing on the accelerations and angular movements of the spine and pelvis using sensor measurements.
• It examines the magnitude of these forces during walking versus cantering and evaluates whether these forces may contribute to overloading and potential injury risk in the low back.

Objective of the Study

• To analyze the accelerations and angular changes occurring in the low back during horse riding, specifically comparing walking and cantering gaits.
• To understand how shock waves generated by horse riding transmit to and affect the spinal segments, and to assess the potential risk of injury due to repeated shocks.

Methodology

• Participants: Twelve female subjects were involved in the study.
• Data collection: Inertial Measurement Units (IMUs) were placed on:
  • The pelvis
  • Three spinal levels: L4, L1, and T11
• Activities:
  • 30 minutes of walking
  • 10 minutes of cantering
• Measurements:
  • Root Mean Squared (RMS) linear accelerations at each sensor location
  • Transmission or signal transfer of acceleration between sensor pairs
  • Angular motions between the IMUs to quantify spinal segment movement

Key Results

• Vertical accelerations at the pelvis:
  • Were significantly higher during cantering than walking
  • Peak RMS acceleration during cantering was 5.52 m/s² at 1.8 Hz, compared to 0.85 m/s² during walking
• Transmission of accelerations between pelvis and spine:
  • At 4 Hz, transmission ratios were around 1 or slightly above, meaning accelerations were passed on equally or amplified
  • For frequencies above 4 Hz, acceleration signals were increasingly damped
  • Damping was most pronounced between the lowest spinal segments (e.g., pelvis to L4)
• Angular changes between pelvis and L4:
  • Rapid angular movements were observed, occurring in less than 0.1 seconds
  • Excessive angular changes up to 30° were recorded
  • High-frequency angular changes suggest involuntary spine movements caused by shocks or impacts

Interpretation and Implications

• Repeated shocks during horse riding result in considerable accelerations transmitted through the pelvis to the lower spine.
• At certain frequencies (around 4 Hz), spinal segments do not effectively dampen these shocks, potentially increasing mechanical stress.
• The observed rapid and sometimes large angular displacements suggest sudden involuntary movements likely linked to impact forces, which might contribute to spine instability or injury.
• Such mechanical loading—both from acceleration and angular displacement—could exceed tissue injury thresholds, therefore representing a risk of low back overloading and injury in horse riders.

Conclusion

• Horse riding, particularly at cantering speeds, produces significant repetitive shock loads on the low back.
• The transmission and partial amplification of these shocks combined with sudden angular motions could overload spinal structures.
• The findings suggest the need for injury prevention strategies focusing on reducing shock transmission or improving spine stabilization during horse riding activities.