THE EFFECT OF SLOPE WALKING ON THE LOWER LIMB MUSCLE FORCE OF HEALTHY ADULTS DURING SELF-PACED TREADMILL WALKING IN A VIRTUAL REALITY ENVIRONMENT: A CROSS-SECTIONAL STUDY

Abstract

Background: Gait is an essential functional activity that requires efficient neuromuscular control to maintain knee joint stability. An integrated coordination of lower limb muscles is crucial to perform the forward motion and maintain knee joint stability, particularly during daily challenging tasks such as slope walking. Biceps femoris (BF), rectus femoris (RF), vastus lateralis (VL), soleus (SOL), and medial gastrocnemius (MG) are important muscles in maintaining knee joint stability during the stance phase of gait. Thus, it is important to understand the individual muscle function during walking on different slopes. However, there are only a few studies that have done so.

Purpose: To investigate the effect of slope walking on lower limb muscle force using the Gait Real-Time Analysis Interactive Lab (GRAIL) on healthy individuals.

Methods: A cross-sectional study with a repeated measure within-subject design included 28 healthy adults (13 males and 15 females; aged 25.02 ± 2.06 years) who walked on a self-paced dual-belt instrumented treadmill under three conditions (-8 °, 0°, +8 °) for 3 minutes at each incline. Muscle force was obtained using the Motek Human Body Model (HBM). The Freidman test and repeated measures ANOVA test were used to examine the impact of slope walking on the lower limb muscle force and walking speed.

Results: Compared to level walking, the walking speed decreased significantly during uphill walking by 0.28 m/s, while there was no significant change observed during downhill walking (P=0.836). During uphill walking, a statistically significant (P=0.001) increase was observed among the BF, SOL, and MG muscle forces. Furthermore, a statistically significant decrease was found in the RF muscle force, while there was no significant difference (P=0.072) in the VL muscle force compared to level walking. Downhill walking significantly (P=0.001) increased the muscle force of RF and VL and significantly decreased the muscle force of BF, SOL, and MG, compared to level walking.

Conclusion: The results indicate that walking uphill increased the muscle forces of BF, MG, and SOL, while downhill walking increased the muscle forces of RF and VL in healthy adults. These findings suggest that different recruitment strategies are developed by the neuromuscular system to aid in successful slope walking. The findings are clinically relevant in encouraging the use of slope walking in rehabilitation programmes to improve patients’ lower limb muscle function to facilitate recovery and maintain knee joint stability.