Evaluation of clinical strength testing and perception of participant with regards to their strength in performing Clamshell exercise in various hip bend positions among healthy adults.

Electromyography (EMG) data of gluteus maximus, gluteus medius and tensor fascia latae (TFL) muscles will be collected from both of the participants’ legs. Alcohol swabs are used to clean the skin over the gluteal and hip region before placement of the Delsys’s surface EMG electrodes according to recommended protocols by Rainoldi and colleagues in 2004. The surface EMG electrodes used in this study are wireless and will only have the 3 electrodes placed per side. To measure gluteus medius muscle activity, the electrode will be placed one-third of the distance between the greater trochanter and the iliac crest, the electrode measuring gluteus maximus muscle activity will be placed one-third of the distance between second sacral vertebra and greater trochanter and the electrode measuring TFL will be placed 75mm from the anterior superior iliac spine, along a line-oriented 30° anterior to the line joining the anterior superior iliac spine and the greater trochanter. Participants' maximal voluntary isometric contraction (MVIC) of the muscles will be tested. MVIC of gluteus maximus muscle will be tested in prone lying with knees flexed to 90° while participants perform resisted hip extension while MVIC of gluteus medius muscle will be tested in side-lying with hips and knees extended at 0° while participants perform resisted hip abduction to 30°, while MVIC testing for TFL is similar but with addition of 45° hip flexion. Next, participants will be instructed to lie on their side on a plinth with their legs together, hips and knees flexed and a pillow supporting their head and neck with their arms by the side. They will be instructed to keep the medial borders of their feet together as they try to abduct and externally rotate their hips. They will be required to practice the exercise at each angle until their technique and execution are deemed as satisfactory with no compensatory actions eg. trunk rotation. Participants will be monitored to ensure their pelvis is maintained in the neutral position as it aids in optimising gluteal muscle recruitment during the clamshell exercise. Once the practice trials are completed, participants would be given 5 minutes to rest before the commencement of the study. Participants will be required to perform four variants of the clamshell exercise at hip angle 0° followed by 30°, 60° and 90°. They will first be shown a demonstration of the clamshell exercise at the four angles tested: 0°, 30°, 60° and 90°. Before each test, hip flexion angle of participants will be adjusted with the use of a goniometer. Next, knee flexion angle is maintained at 90°. A researcher will perform manual muscle testing (MMT) of the hip muscles in the clamshell exercise at each of the hip angles before MVIC testing. MMT will be done in accordance with Medical Research Council Manual Muscle Testing and the researcher will grade the strength accordingly. Next, participants will need to perform three consecutive 5 seconds MVIC at each hip angle with 3 minutes rest in between each test angle. A luggage belt will be strapped around the plinth and the lateral condyle of participants’ femur to ensure standardization. At the end of the tests, participants will be asked to rank the angles in which they felt was the strongest to weakest in performing the clamshell exercise. The approximate total duration of the testing session is 60 minutes. Participant will attend the session once. A registered physiotherapist will monitor and recommend adjustment to the positioning of the participant.