Altered timing in trunk rotation with the ToneFit Reha compared to Nordic Walking in people with low back pain

Summary: This study compared the trunk rotation during walking with the ToneFit Reha (TFR), a product with push-pull resistance handles, and Nordic Walking. The TFR resulted in a delayed reversal of trunk rotation towards the end of the second double support phase. This change in timing allowed to manage the challenged balance when walking with the TFR. Introduction: Physical activity is widely used for the treatment of low back pain (LBP). Nordic Walking (NW) has been used as an exercise to increase the benefits of walking in such population resulting in increased core stability. The ToneFit Reha (TFR) is a newly developed product, worn around the waist. It mimics normal walking but with added push-pull handles with adjustable resistance. The TFR is intended for rehabilitation, allowing individual settings for each person and each side of the body. The aim of this study was to determine the effect of walking with the TFR on trunk rotation compared to NW. Methods: Ten participants with LBP (age 42.1 ± 5.4 years, mass 71.4 ± 8.0 kg, height 172.1 ± 5.2 cm) were recruited. After signing informed consent, retro-reflective markers were added to the spine and arm and a familiarization period for each condition was allowed. Each participant performed ten trials with NW followed by the TFR at the same speed. Marker trajectories were recorded using 12 Vicon cameras (240 Hz, Vicon Vantage, Vicon Motion Systems Ltd, UK). Trunk rotation angles, shoulder flexion angles as well as durations of double and single support phases were averaged over the left and right side and of all trials per participant for statistical analysis. A paired t-test with Bonferroni adjustment resulting in a significance level of 0.01 was used to determine statistically significant differences between conditions. Results and Discussion: While the peak contralateral trunk rotation angle did not differ between TFR and NW, the peak occurred later during TFR. Further, the first double support phase was significantly longer while the second single support phase was significantly shorter for TFR. The timing of the peak shoulder flexion (indicating the reversal of the arm movement) did not differ between TFR (43% of gait cycle) and NW (45% of gait cycle). During TFR, the push-pull movement with the handles needed to be counterbalanced by the trunk. Changing the direction of the trunk rotation while simultaneously generating enough force to stabilize against the applied force at the handles, is a challenging task. It is concluded that this challenge was met by delaying the directional change of the trunk rotation towards the end of the second double support phase. The increased base of support during this phase provides more stability to the body. Also, due to this delay, the leading arm was closer to the body when the change of trunk rotation occurred. Therefore, the lever arm was smaller resulting in less force needed in the trunk to keep the upper body stable. Conclusions: The TFR caused significant changes in the timing of the trunk rotation to manage the increased challenges due to instability. If this added challenge in stability and the chosen strategy is beneficial for rehabilitation, will need to be determined in future research