Sahabuddin, Farhah Nadhirah Aiman
(2022)
Biomechanics of single leg squat in physically active females: influence of dynamic knee valgus and exercise intervention.
Masters thesis, Universiti Sains Malaysia.
Abstract
Dynamic knee valgus (DKV) is generally associated with non-contact lowerlimb
injuries, particularly in females. Thus, Study 1 compares the lower limb joints
kinematic among physically active females with and without excessive DKV during
single leg squats (SLS) at 45° and 60° knee flexion. Thirty four females were enlisted
and categorized into two groups (i.e., normal and excessive DKV) based on the results
of the drop vertical jump screening test. A DKV evaluation is based on the average
knee FPPA range which is 7° to 13° for females in normal DKV group, while those in
excessive DKV group have more than 13° of knee FPPA range. The 3-Dimensional
(3D) SLS test (45° and 60° knee flexion) executed by the participants were captured
with a Qualisys Track Manager System and analysed the kinematic data using an
independent T-test. During 45° knee flexion, the dominant leg of normal DKV group
showed a higher hip adduction angle (4.49±3.25°, t(32) = 2.371, p= 0.024) than the
excessive DKV group (1.426±4.23°). Moreover, the normal DKV group displayed
knee adduction (1.72±6.14°, t(32) = 2.291, p= 0.029), but the excessive DKV group
demonstrated knee abduction (-3.620±7.40°) during SLS with dominant leg. During
60° knee flexion, the normal DKV performed with adducted dominant knee
(0.223±0.07°, t(16.048) = 10.707, p=0.000) but abducted in the excessive DKV group
(-4.478±1.81°). During 60° knee flexion with the non-dominant leg, the normal DKV
group demonstrate SLS test with abducted knee (-1.127±0.89°, t(21.410) =-6.863, p=
0.000) while adducted in the excessive DKV group (0.635±0.57°). Furthermore, the non-dominant hip angle was abducted in the normal DKV group (0.635±0.54°,
t(21.567) = 6.225, p= 0.000) but adducted (-0.245±0.23°) in the excessive DKV group
during SLS. Therefore, females with excessive DKV had considerably different lower
limb kinematics and movement control techniques than females with a normal DKV
range. The findings emphasized the significance of DKV screening among physically
active females, including the rationale for endorsing personalized exercise
interventions to avoid lower limb non-contact injuries. Thus, the aim of Study 2 was
to examine the effect of four weeks hip- and ankle-focused exercises on lower limb
mechanics during SLS among physically active females. Thirty-six physically active
females with excessive DKV, i.e., greater than 13° knee frontal plane projection angle
(FPPA), were assigned equally to three groups: HIP, ANKLE, or control. Throughout
12 sessions across four weeks, the intervention groups underwent exercises focusing
on either the hip (HIP group) or ankle (ANKLE group) musculatures. A training plan
was not given to the control group. Next, all three groups demonstrated a similar SLS
test protocol from study 1 (i.e., 45º and 60° of squat depths) were capture before and
after intervention. A two-way ANOVA test was used to assess the data. During 45°
SLS, there were interaction effects in the dominant knee (F (2.66) = 9.437, P = 0.001)
and ankle (F (2.66) = 16.465, P = 0.001) sagittal moment between groups throughout
four-weeks intervention. Meanwhile, the interaction effects in the hip extension angle
for the dominant (F(2.66) = 12.032, P = 0.001) and non-dominant leg (F(2.66) = 3.618,
P = 0.032) between groups were identified during 60° SLS after intervention. A fourweek
intervention of hip-focused exercises affected lower limb biomechanics during
SLS, especially in the sagittal plane. Thus, strengthening hip muscles, particularly the
hamstring and quadriceps, through exercise may help to minimise excessive DKV in
physically active females.
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