INVESTIGATION OF EMG ACTIVITY OF THE LOWER LIMB MUSCLES DURING FORWARD STEP-UP EXERCISE IN LAND AND UNDER IMMERSION IN ADULTS

B.C.L. So¹, M.M.Y. Kwok¹, N.W.L. Lee¹, A.W.C Lam¹, A.L.M. Lau¹, A.S.L. Lam¹, P.W.Y. Chan¹, S.S.M. Ng¹

¹The Hong Kong Polytechnic University, Rehabilitation Sciences, Hong Kong, China

Background: Step-up is one of the most common functional tasks related to locomotion and an essential requirement for lower limb physical activity. Forward step-up (FSU) exercise simulates the stance phase in stair ascension in activities of daily livings. It has also been adopted as an exercise modality to improve muscle power oflower limbs. Compared with land stepping, with the benefits of physical properties of water, the advantages of aquatic stepping when compared to land stepping remain unknown. A reduced perceived tiredness and joint loading of FSU conducted in aquatic environment could potentially reduce the risk of musculoskeletal injuries.

Purpose: 1. Here we strive to investigate the surface electromyography (sEMG) activities of gluteus maximus (GM), biceps femoris (BF), rectus femoris (RF) and gastrocnemius (GA), when performing FSU exercise with different speeds in water and land.

Methods: Twenty healthy participants (10 males, 10 females) were recruited by convenience sampling. Participants were instructed to perform FSU exercises at different speeds (35, 60, 95 bpm) of 3x8 repetitions in water and on land. The sEMG of GM, RF, GA and BF muscles in water and on land were collected and the knee motions were analyzed by motion-tracking software Kinovea (v.0.9.5) (Kinovea, Bordeaux, Nouvelle Aquitaine, France). The mean percentage maximal voluntary contraction (%MVC) between the four muscles was compared. The %MVC of GM, RF, GA and BF at different speed was also identified.

Results: There was a statistically significant difference of %MVC of RF at all speed when compared in ascending and descending phase conducted on land and in aquatic environment (P<0.01). When considered land ascending and descending phase at the three speeds tested, there were significant changes between 35 bpm VS 60 bpm, 35 bpm VS 95 bpm, 60 bpm VS 95 bpm (P<0.01). In aquatic ascending phase, there were significant changes between 35 bpm VS 60 bpm, 35 bpm VS 95 bpm, 60 bpm VS 95 bpm (P<0.01) as well as in descending phase (P<0.05). For the other 3 muscles, the difference of %MVC does not have statistically significant differences at all speed in both movement phases and environments.

Conclusions: This study found a difference of mean percentage MVC of the tested muscles between land and aquatic environment at various speeds of stepping. All tested muscles’ activity reduced under immersion when compared to FSU performed on land.

Implications: The findings of this study can provide valuable insights regarding the application of FSU. The unique physical properties of water allowed aquatic FSU to serve as a knee exercise alternative for individuals presented with lower weight bearing abilities or high levels of knee pain. This could be an efficacious approach for health professionals when designing individualized programs targeted on activation lower limb muscle activities in aquatic environment.

Funding acknowledgements: N/A

Keywords:
muscles activity
stepping exercises
water immersion

Topics:
Musculoskeletal: lower limb
Health promotion & wellbeing/healthy ageing/physical activity

Did this work require ethics approval? Yes

Institution: The Hong Kong Polytechnic University

Committee: The Hong Kong Polytechnic University

Ethics number: HSEARS20220311001