Fascicle Length Change of the Human Tibialis Anterior and Vastus Lateralis During Walking

1. Fascicle Length Change of the Human Tibialis Anterior and Vastus Lateralis During Walking Tony Hernandez Amrik Sidhu PT 212

2. Introduction Force determined by movement type Eccentric (lengthening) Concentric (shortening) Isometric Force/Velocity Relationship Force decreases with increased speed Force increases with eccentric action

3. Introduction Optimal force at certain muscle length Kinematics/EMG to determine muscle action (concentric/eccentric/isometric) Tendon & aponeurosis length effects Eccentric plantar flexors control tibial advancement during mid/terminal stance Medial gastroc remains at constant length

4. Introduction Cont. Vastus lateralis lengthen during eccentric & shorten during concentric -- interaction between fascicles/tendon is muscle specific Role of TA Control foot during heel contact Allows foot clearance via dorsiflexion Role of VL After heel contact controls knee flexion End of swing insures knee extension for ground contact

5. Introduction Cont. TA & VL lengthen (eccentric) in stance TA & VL shorten (concentric) in swing PURPOSE: determine fascicle length change in TA and VL during gait

6. Subjects 9 healthy college age volunteers completed the study (only 7 for VL data) Exclusion: orthopedic/neurologic problems, fracture, torn ankle lig, nerve compression, pain from nerve compression

7. Methods Ultrasonography Image TA/VL fascicles at mid-belly for optimal view 1/10 strides per video frame for length measurement Fascicle measured along diagonal fibers Secured over longitudinal axis

8. Methods A)TA Fascicle shortened at 0% gait cycle B)TA Fascicle lengthened at 64% gait cycle C)VL Fascicle shortened at 0% gait cycle D)VL Fascicle lengthened at 75% gait cycle

9. Methods Cont. Joint Kinematics/EMG Determine muscle activity of TA/VL Electrogoniometers to determine knee/ankle angle 8 strides for each subject were averaged

10. Procedures Treadmill walking at average walking speed (1.3m/s) Muscle activity, fascicle length, & joint angle data collected simultaneously Several strides over 5-10sec One stride chosen for analysis

11. Results -TA Ankle angle Ankle ROM significantly different throughout most of gait cycle Fascicle Length Lengthened at middle of gait cycle Shortened at 3/4 gait cycle EMG signal Highest activity at beginning, middle, and end of gait cycle

12. Results-TA

13. Results -VL Knee Angle Significantly different between each consecutive time in gait cycle Fascicle Length Lengthened significantly at mid-cycle Shortened significantly at 3/4 to end of cycle Did not change in 1st and 2nd portions of cycle EMG signal Active in 1st portion of stance Active at end of swing phase

14. Results-VL

15. Discussion Functions of TA Controls foot lowering to ground Dorsiflexes foot during swing insuring toe clearance Functions of VL Controls knee flexion after heel contact Insures knee extension in terminal phase

16. Discussion Cont. Fascicles remain at constant length as ankle plantar flexes and knee flexes suggesting isometric contraction Lengthening of muscle-tendon in TA/VL is likely due to lengthening of tendon & its extension into the muscle

17. Discusison Cont. During stance TA/VL muscle action mostly isometric despite muscle-tendon lengthening Gives muscle potential to produce high forces May help avoid muscle injury from eccentric actions

18. Conclusion TA/VL appear isometric during beginning stance despite change in joint angle Allows high force potential, avoid injury TA/VL fascicles shorten as ankle DF suggesting concentric action Interaction between fascicle and tendon allows joint motion by tendon lengthening

19. Thank You Question?