Journal of Orthopaedic & Sports Physical Therapy - Gary S. Chleboun, PT, PhD

Vastus Lateralis Fascicle Length Changes During Stair Ascent and Descent

Gary S. Chleboun, Sarah T. Harrigal, James Z. Odenthal, Laura A. Shula-Blanchard, Jennifer N. Steed

STUDY DESIGN: Experimental descriptive laboratory study. OBJECTIVES: To describe the change in fascicle length of the human vastus lateralis (VL) muscle during the stance phase of stair ascent and descent. BACKGROUND: Muscle fascicle length changes during lower limb functional activities, such as walking and jumping, do not always coincide with joint angle changes. METHODS AND MEASURES: Thirty-three healthy, college-age women walked up and down 4 standard steps. VL fascicle length and pennation angle were measured using real-time ultrasonography. Knee angle was monitored using an electrical goniometer. Foot switches indicated foot contact and release. VL muscle activity was monitored using surface electrodes. The VL muscle-tendon complex and tendon length were calculated based on published models. RESULTS: During initial weight acceptance in stair ascent, the knee joint extended only 3°, VL muscle activity increased to a maximum, VL fascicles shortened, and the tendon lengthened. As the knee extended to ascend the step, the fascicles and tendon shortened throughout the movement. During weight acceptance in stair descent, VL muscle activity increased, VL fascicle length did not change significantly, but the tendon lengthened as 10° of knee flexion occurred. As the knee flexed to complete descent, VL muscle activity peaked, and VL fascicles and tendon lengthened. CONCLUSION: VL fascicles shorten and lengthen as expected during the respective knee extension and knee flexion phases of stair ascent and descent. However, during initial weight acceptance in both stair ascent and descent, the fascicle length change did not coincide with the knee joint kinematics.

J Orthop Sports Phys Ther. 2008;38(10):624-631, published online 11 July 2008. doi:10.2519/jospt.2008.2816

KEY WORDS: knee, muscle-tendon complex, quadriceps, tendon, ultrasonography

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

Gary S. Chleboun, Anna B. Busic, Kristian K. Graham, Heather A. Stuckey
STUDY DESIGN: A single-group descriptive experimental design. OBJECTIVES: To determine the fascicle length change in the tibialis anterior (TA) and the vastus lateralis (VL) muscles during walking. BACKGROUND: The length of the muscle fibers during isometric actions and during dynamic functional activities is affected by the compliance of the tendon and aponeurosis. The TA and VL muscles have important functions both in stance and swing phases of gait. Therefore, it is important to understand the dynamics of the muscle length change as it relates to the type of muscle actions in walking. METHODS AND MEASURES: Nine healthy subjects performed treadmill walking while fascicle length, muscle activity (electromyographic signal), and joint angle (knee and ankle) were recorded. Fascicle length was measured using real-time ultrasound imaging. Fascicle length and joint angle during the gait cycle were analyzed using a repeated-measures analysis of variance. RESULTS: During the initial portion of stance when the TA and VL muscles were active, the ankle plantar flexed and the knee joint flexed, suggesting muscle-tendon complex lengthening, but the fascicle length of both muscles remains constant (TA: P=.93; VL: P=.22). The TA muscle was again active during the initial portion of swing phase while the ankle dorsiflexed, and the fascicle length decreased (P<.05). The VL muscle became active again at the end of swing as the knee extended, and the fascicle length decreased (P<.05). CONCLUSIONS: The lack of change in fascicle length during the initial portions of stance phase suggests a nearly isometric muscle action of the TA and VL. There is a possible interaction occurring between the fascicle and tendon in the TA and VL such that the tendon lengthens to allow joint motion and potentially to store elastic energy.

J Orthop Sports Phys Ther. 2007;37(7):372-379, published online 16 April 2007. doi:10.2519/jospt.2007.2440

KEY WORDS: muscle architecture, tendon compliance, ultrasound

Effect of Cessation and Resumption of Static Hamstring Muscle Stretching on Joint Range of Motion

Richard W. Willy, Bryan A. Kyle, Shawn A. Moore, Gary S. Chleboun

Study Design: Single group repeated measures. Objectives: To determine the effects of cessation and resumption of a hamstring muscle stretching protocol on knee range of motion (ROM). Background: It is generally accepted that stretching exercises result in an increase in ROM. The ability to maintain ROM once stretching has ceased and the ability to regain ROM after resumption of the stretching exercise is not well known. Methods and Measures: Evaluated the effect of 6 weeks of static hamstring stretching, 4 weeks with cessation from stretching, and 6 weeks with resumption of stretching on knee ROM in 18 inactive college students (12 men, 6 women, mean age 21.0 years). The hamstring stretching consisted of 2 30-second stretches per day, 5 days per week. Knee ROM was measured before and after each of the above phases with an active knee extension test. Results: Mean knee ROM increased after the initial stretching period (143 ± 11° to 152 ± 9°), decreased to baseline following the cessation period (145 ± 8°) and again increased following the resumption of stretching but was not different from the initial gains (154 ± 10°). Unlike the stretch limb, the control limb ROM did not change over the 4 measurement times. Conclusions: There was no retention of knee ROM 4 weeks following a 6-week stretching protocol and a subsequent stretching period did not enhance the gain of knee ROM over the initial stretching period.

J Orthop Sports Phys Ther. 2001;31(3):138-144.

Key Words: muscle flexibility, rehabilitation