(378) Leg Dominance May Influence Exercise-Induced Hypoalgesia Response to Moderate Intensity Retrowalking: A Pilot Study

Abstract

Retrowalking (walking backwards) is often used clinically to address movement impairment. Whether retrowalking at a moderate intensity is sufficient to produce exercise-induced hypoalgesia (EIH) is unknown. This pilot study explored EIH following retrowalking in twenty healthy young adults (21.6 ± 2.9 yrs, 10 men). Pressure pain thresholds (PPTs) were assessed at bilateral quadriceps and left index finger nailbed utilizing a computerized pressure algometer (Medoc AlgoMed) pre/post 20 minutes quiet rest (session 1) and pre/post 20 minutes of retrowalking at 45-55% heart rate reserve (session 2). Participants pressed the indicator button when the applied pressure first became painful. The average of three trials at each site was used for PPT and site order was randomized between sessions. A significant trial x site interaction was identified. Post hoc testing revealed no significant trial effects after quiet rest at any site. After retrowalking, only the right quadriceps showed an increase in PPT (417.8 ± 146.3 vs 380.5 ± 122.8 kPa). Although baseline PPTs were significantly lower in the right quadriceps than the left in session 1 (362.9 ± 107.2 vs 395.1 ± 127.9 kPa), this difference did not reach significance in session 2 (380.5 ± 122.8 vs 417.4 ± 174 kPa). In both sessions, PPT of the right quadriceps increased to match that of the left (Quiet Rest: 383.8 ± 117.9 vs 382.7 ± 148.6 kPa; Retrowalking: 417.8 ± 146.3 vs 418.9 ± 167.8 kPa). Of the twenty participants, 18 reported right leg dominance, 1 left, and 1 failed to report. Our pilot data suggests that pain sensitivity and EIH response to retrowalking may vary based upon leg dominance; therefore, unilateral assessment of EIH with bilateral working muscles could produce spurious outcomes. Further investigation into the potential role of leg dominance on pain reports before and after this novel exercise task is warranted. Retrowalking (walking backwards) is often used clinically to address movement impairment. Whether retrowalking at a moderate intensity is sufficient to produce exercise-induced hypoalgesia (EIH) is unknown. This pilot study explored EIH following retrowalking in twenty healthy young adults (21.6 ± 2.9 yrs, 10 men). Pressure pain thresholds (PPTs) were assessed at bilateral quadriceps and left index finger nailbed utilizing a computerized pressure algometer (Medoc AlgoMed) pre/post 20 minutes quiet rest (session 1) and pre/post 20 minutes of retrowalking at 45-55% heart rate reserve (session 2). Participants pressed the indicator button when the applied pressure first became painful. The average of three trials at each site was used for PPT and site order was randomized between sessions. A significant trial x site interaction was identified. Post hoc testing revealed no significant trial effects after quiet rest at any site. After retrowalking, only the right quadriceps showed an increase in PPT (417.8 ± 146.3 vs 380.5 ± 122.8 kPa). Although baseline PPTs were significantly lower in the right quadriceps than the left in session 1 (362.9 ± 107.2 vs 395.1 ± 127.9 kPa), this difference did not reach significance in session 2 (380.5 ± 122.8 vs 417.4 ± 174 kPa). In both sessions, PPT of the right quadriceps increased to match that of the left (Quiet Rest: 383.8 ± 117.9 vs 382.7 ± 148.6 kPa; Retrowalking: 417.8 ± 146.3 vs 418.9 ± 167.8 kPa). Of the twenty participants, 18 reported right leg dominance, 1 left, and 1 failed to report. Our pilot data suggests that pain sensitivity and EIH response to retrowalking may vary based upon leg dominance; therefore, unilateral assessment of EIH with bilateral working muscles could produce spurious outcomes. Further investigation into the potential role of leg dominance on pain reports before and after this novel exercise task is warranted.