The method reported was followed in a study that received ethical approval from the Bournemouth University Research Ethics Committee (Reference 15005).

1. Participants

1. Recruit healthy adults (aged from 23 to 63 years, mean ± S.D.; 42.0 ± 13.4, body mass 70.4 ± 15.3 kg, height 175.5 ± 9.8 cm; 15 males, 15 females) to participate in the study. Thirty participants were recruited for this study.
2. Ensure that there is no self-reported history of dizziness, balance problems or walking difficulties in the participants.
3. Ensure that participants did not suffer from any known neuromuscular injury or condition affecting balance or walking.

2. Setup and procedures for gait analysis

1. Use a gait analysis system (Figure 1) comprised of a dual-belt force plate-instrumented treadmill, a 10-camera motion capture system and a virtual environment that provides optic flow.
2. Ensure that the participant is wearing very tight non-reflective clothing such as cycling shorts or leggings.
3. Using double sided adhesive tapes attach 25 passive reflective markers and place according to the lower body configuration of the Human Body Model (HBM)⁷ as detailed in Table 1 and Figure 2. The information in this document is taken from the HBM Reference Manual⁸.
4. Use a joint ruler to take measurements of the required knee and ankle widths for the HBM⁶.
5. Secure participant to a safety harness that is fastened to an overhead frame.
6. Start a new session in the database and make sure it is active (highlighted).
7. Using the subject tab, create a new participant from the Labeling Skeleton button.
8. Browse to the 'LowerLimb HBM_N2.vst' file and then enter the name of the participant. The new participant appears in the Subjects pane.
9. Go to the Tools pane and open the Subject Preparation tab.
10. Zero level the forceplates via the Hardware tab. Make sure that no weight is exerted on the force plates.
11. Prepare the participant for the ROM trial by having them ready in the middle of the treadmill.
12. To ensure the participant can accustom themselves to the self-paced treadmill, ask them to walk at a comfortable speed for 5 min at the beginning of the session^9,10.
13. Following the acclimatization and without any delay time, ask the participant to walk for a minimum of 5 min^10,11.
14. Ensure participants are blinded to the timing of the recordings.
15. Ensure to start the treadmill and start data recordings by clicking the Start recording button¹². This can be done with integrated software (Table of Materials).
16. Stop the recording after acquiring the desired amount of data. It is recommended to collect three sets of 25 cycles.
17. Open the processing software (Table of Materials) and remove the high-frequency noise on data, by selecting a low-pass filter to the marker data such as a second order Butterworth filter with a cut-off frequency of 6 Hz.
18. Go to File, and then select Export to save as a .csv.
19. Determine individual strides from vertical force data and use the foot markers to ascertain gait events¹³.
20. Analyze the gait parameters such as kinematic, kinetic and spatial-temporal data in Matlab R2017a (Supplementary File).

3. Setup and procedures for muscle strength test

1. Use the muscle strength testing equipment (multimodal dynamometer) (Figure 3), to measure participants' muscle strength based on Maximum Voluntary Isometric Contraction (MVIC)¹⁴.
2. Attach the tool/pad number 701 to the dynamometer exercise head.
3. Test participant's right and left knee isometric muscle strength.
4. Test participants in a seated position on a chair with a backrest.
5. Using the up/down switch, align the dynamometer axis with the knee joint's anatomical axis of rotation. Place the pad of the tool centrally at the lower part of the shin of the tibia.
6. Keep the knee at 90° flexion, the hip in neutral rotation and abduction, and the foot in plantar flexion.
7. Place the participant's hands on their abdomen and stabilize the trunk, hips, and mid-thigh on the chair with Velcro straps.
8. Run a practice trial for participants to get accustomed to the testing maneuver.
9. Instruct the participant to extend their knee (exert pressure upwards on the pad) followed by flex (exert pressure downwards on the pad) to exert a maximum contraction on the command Go for 3 s.
10. Provide verbal prompts and encouragement ("Push" for upwards and "Pull" for downwards) during the strength testing.
11. Ensure that participants are aware they can stop the test immediately if they experience any unusual pain or discomfort.
12. Allow participants to rest for 2 min.
13. Repeat steps 3.1 – 3.12, three times for the left leg and right leg and record the data in newtons (N).
14. Save all the data and export as a report for the analysis.