The Effect of Knee Position on Calf Raise Test Outcomes in Healthy Adults

This is a randomised cross-over study performed in a biomechanics laboratory to develop and examine a seated knee-bent version of the standing calf raise test. This study will therefore compare the effect of knee position (knee extended in standing vs knee flexed in seated) on calf raise test outcomes, with the seated calf raise test considered as the intervention and the standing calf raise test considered as the control. The intervention (seated knee bent to 90 degrees) and control (standing knee straight at 0 degrees) conditions will be assessed in one main session, allocated in a randomised order and separated by 30 minutes of rest (inclusive of 5 minutes walking recovery). Both conditions will use standardised verbal instructions, an iPad-based Calf Raise App for 2D video recording of foot movement, force plates, 3D motion capture, and surface electromyography. Paper-based or tablet-based forms will also be used to collect baseline information, perceived exertion, perceived muscular loading location, and overall calf muscle fatigue. Participants will attend one laboratory session in a human movement biomechanics laboratory. After providing written informed consent, participants will complete a short baseline questionnaire, undergo preparation for surface electromyography, complete a standardised warm-up and familiarisation trials, and perform maximal voluntary isometric plantarflexor strength tests in seated and standing positions. Participants will then complete the seated or standing calf raise test to fatigue. The test involves repeated heel lifts to fatigue. Participants will be instructed to lift the heel as high as possible and return to the starting position using a standardised cadence, success criteria, and stopping rules, as per published protocols by Hebert-Losier et al. Performance outcomes will include number of repetitions, total mechanical work, and maximum heel-rise height. Muscle activity and fatigue will be recorded using surface electromyography from the soleus and gastrocnemius muscles during the main testing session. Perceptual responses will be collected after the test using rating scales and a body map. Following 30 minutes of rest that includes a 5 minutes active walking recovery on a treadmill, the alternate calf raise test will be completed. All testing will be conducted barefoot for standardisation. The intervention will be delivered and supervised for adherence face to face and individually by members of the research team. The team includes trained physiotherapists, strength and conditioning coaches, and sport scientist with human movement expertise and laboratory-based human performance testing. The main testing session will take approximately 70 to 80 minutes in total. Participants will also be invited to complete an optional second session 3 to 14 days later to assess test-retest reliability. The reliability session will take approximately 20 to 25 minutes. For the reliability session, electromyography will not be collected, and participants will complete one endurance test only. If reliability sample size is not reached from the main study cohort, additional participants will be recruited. The intervention is not intended to be therapeutic and will not be personalised, titrated, or adapted for treatment purposes. Standardisation will be maintained across participants through consistent instructions, warm-up, familiarisation, cadence, success criteria, stopping rules, testing procedures, and laboratory set-up. Participant safety will be supported by eligibility screening, inclusion of healthy and at least moderately active adults, adequate rest between tests, and monitoring by the research team during testing. Intervention fidelity will be assessed and maintained through use of the same standardised testing protocol, equipment, participant instructions, and outcome recording procedures across sessions. Research team members will follow the approved protocol during all testing. Performance data from the Calf Raise App, 3D motion capture, force plates, and, where applicable, surface electromyography will be used to confirm that the test was delivered and recorded as planned.