Acute Effects of Multi-joint Eccentric Exercise on Lower Extremity Muscle Activation Measured During Land and Water Walking

Aquatic walking combined with lower-body eccentric exercise provides a low-impact, time-efficient method for improving strength and mobility. While both modalities show promise individually, it is unclear if neuromuscular activation patterns during aquatic walking remain consistent following a short bout of submaximal eccentric exercise. PURPOSE: To compare lower-extremity muscle activation during walking performed in chest-deep water versus on land, before and after a short bout of eccentric exercise. METHODS: Twenty-six healthy, recreationally active young adults completed the study (male = 16; female = 10; age = 21.6 ± 2.5 years; height = 176.4 ± 6.9 cm; mass = 75.9 ± 13.3 kg). Each participant walked on both land and aquatic treadmills at 2.5 mph for 2 minutes, before and after performing eccentric exercise at 40% submaximal effort. During these sessions, root-mean-square (RMS) muscle activity of the tibialis anterior (TA), medial gastrocnemius (GM), biceps femoris (BF), and vastus lateralis (VL) was recorded using surface electromyography, focusing on the swing and stance phases of gait. A two-way within-subjects analysis of variance (ANOVA) was conducted to assess main effects and interactions between conditions. RESULTS: Thigh co-activation (BF/VL) increased following eccentric exercise during swing on land (427 ± 234% vs. 279 ± 134%; p = 0.005), whereas no significant changes were observed post-eccentric exercise during swing in water (p = 0.859). VL RMS was 20% lower during stance in water (17 ± 8 μV vs. 21 ± 12 μV; p = 0.036) and 46% greater during swing in water (19 ± 7 μV vs. 13 ± 10 μV; p < 0.001). BF RMS was 51% greater during stance in water (38 ± 21 μV vs. 25 ±19 μV; p = 0.002), while no differences were observed in BF RMS during swing between the two environments (p = 0.699). TA RMS during swing was 28% greater in water (96 ± 33 μV vs. 75 ± 29 μV; p < 0.001), while GM RMS during swing was 27% lower in water (11 ± 7 μV vs. 15 ± 10 μV; p = 0.019). TA RMS during stance was 16% lower in water (52 ± 19 μV vs. 62 ± 20 μV; p = 0.011), while GM RMS during stance was 34% lower in water (56 ± 23 μV vs. 85 ± 34 μV; p < 0.001). CONCLUSION: Aquatic treadmill walking alters lower-extremity neuromuscular activation patterns compared to land treadmill walking, with consistent changes observed before and after a short bout of eccentric exercise.