Journal of Orthopaedic & Sports Physical Therapy® Downloaded from www.jospt.org at Northeastern University Libraries on February 19, 2015. For personal use only. No other uses without permission. Copyright © ${year} Journal of Orthopaedic & Sports Physical Therapy®. All rights reserved.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29
Changes in Quadriceps and Hamstring Co-contraction Following Landing Instruction in Patients with ACL Reconstruction
Audrey R.C. Elias, PT, DPT, OCS1 Curt D. Hammill, MS1 Ryan L. Mizner, PT, MPT, PhD1
1
School of Physical Therapy and Rehabilitation Sciences, University of Montana, Missoula, MT.
The project was reviewed and approved by the Institutional Review Board of the University of Montana. The authors certify that they have no affiliations with or financial involvement in any organization or entity with a direct financial interest in the subject matter or materials discussed in the article. Address correspondence to Ryan L. Mizner, University of Montana, 32 Campus Drive, Skaggs 109, Missoula, MT 59812, [email protected].
Journal of Orthopaedic & Sports Physical Therapy® Downloaded from www.jospt.org at Northeastern University Libraries on February 19, 2015. For personal use only. No other uses without permission. Copyright © ${year} Journal of Orthopaedic & Sports Physical Therapy®. All rights reserved.
30 1
STUDY DESIGN: Pre-test/post-test controlled laboratory study.
2
OBJECTIVES: To determine changes in the neuromuscular activation of the quadriceps
3
and hamstrings following instructions aimed at improving knee flexion during a single
4
limb landing task in persons who have undergone anterior cruciate ligament (ACL)
5
reconstruction.
6
BACKGROUND: Clinicians advise patients who have undergone ACL reconstruction
7
(ACLR) to increase knee flexion during landing tasks to improve impact attenuation.
8
Another longstanding construct underlying such instruction involves increasing co-
9
contraction of the hamstrings with the quadriceps to limit anterior shear of the tibia on
10
the femur. The current study examined if co-contraction of the knee musculature
11
changes following instruction to increase knee flexion during landing.
12
METHODS: Thirty-four physically active subjects with unilateral ACLR participated in a
13
one-time testing session. The kinetics and kinematics of single leg landing of the
14
surgical limb were analyzed before and after instruction to increase knee flexion and
15
reduce the impact of landing. Vastus lateralis and biceps femoris activities were
16
analyzed using surface EMG and normalized to a maximal voluntary isometric
17
contraction (MVIC). Co-contraction indices were integrated over the weight acceptance
18
phase of landing.
19
RESULTS: Following instruction, peak knee flexion increased (mean ± SD; pre:
20
56°±11°; post: 77°±12°; p
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29
Changes in Quadriceps and Hamstring Co-contraction Following Landing Instruction in Patients with ACL Reconstruction
Audrey R.C. Elias, PT, DPT, OCS1 Curt D. Hammill, MS1 Ryan L. Mizner, PT, MPT, PhD1
1
School of Physical Therapy and Rehabilitation Sciences, University of Montana, Missoula, MT.
The project was reviewed and approved by the Institutional Review Board of the University of Montana. The authors certify that they have no affiliations with or financial involvement in any organization or entity with a direct financial interest in the subject matter or materials discussed in the article. Address correspondence to Ryan L. Mizner, University of Montana, 32 Campus Drive, Skaggs 109, Missoula, MT 59812, [email protected].
Journal of Orthopaedic & Sports Physical Therapy® Downloaded from www.jospt.org at Northeastern University Libraries on February 19, 2015. For personal use only. No other uses without permission. Copyright © ${year} Journal of Orthopaedic & Sports Physical Therapy®. All rights reserved.
30 1
STUDY DESIGN: Pre-test/post-test controlled laboratory study.
2
OBJECTIVES: To determine changes in the neuromuscular activation of the quadriceps
3
and hamstrings following instructions aimed at improving knee flexion during a single
4
limb landing task in persons who have undergone anterior cruciate ligament (ACL)
5
reconstruction.
6
BACKGROUND: Clinicians advise patients who have undergone ACL reconstruction
7
(ACLR) to increase knee flexion during landing tasks to improve impact attenuation.
8
Another longstanding construct underlying such instruction involves increasing co-
9
contraction of the hamstrings with the quadriceps to limit anterior shear of the tibia on
10
the femur. The current study examined if co-contraction of the knee musculature
11
changes following instruction to increase knee flexion during landing.
12
METHODS: Thirty-four physically active subjects with unilateral ACLR participated in a
13
one-time testing session. The kinetics and kinematics of single leg landing of the
14
surgical limb were analyzed before and after instruction to increase knee flexion and
15
reduce the impact of landing. Vastus lateralis and biceps femoris activities were
16
analyzed using surface EMG and normalized to a maximal voluntary isometric
17
contraction (MVIC). Co-contraction indices were integrated over the weight acceptance
18
phase of landing.
19
RESULTS: Following instruction, peak knee flexion increased (mean ± SD; pre:
20
56°±11°; post: 77°±12°; p
