| Summary: | INTRODUCTION. Muscle weakness and biomechanical alterations have been
recognized as risk factors for various running-related injuries (RRIs), fuelling a growing
interest in understanding the relationship between strength and running biomechanics.
While existing research has predominantly focused on the relationship between hip
strength and kinematics, other potential associations remain largely unexplored.
Moreover, many studies have employed isometric strength testing, which may not
accurately reflect muscle function during running. Notably, there is a lack of research on
novice runners, despite their heightened susceptibility to RRIs. Consequently, the
purpose of this thesis is to investigate the association between lower-limb isokinetic
strength and running kinematics in healthy novice runners.
METHODS. 10 male and 10 female novice runners participated in this study. 3D
running kinematic data was collected using a marker-based motion capture system
(Vicon). Peak isokinetic strength of the hip abductors and adductors, knee flexors and
extensors, as well as the ankle plantarflexors, dorsiflexors, invertors and evertors was
measured using an isokinetic dynamometer (Biodex System 4 Pro). Spearman
correlation coefficients were used to determine the relationship between lower-limb
isokinetic strength and stance phase running kinematics.
RESULTS. Isokinetic hip abductor strength was significantly correlated to frontal plane
hip kinematics in male novice runners (toe-off angle: r = -0.620, p = 0.004; minimum
angle: r = -0.624, p = 0.003), but no such correlations were found in females. Overall,
the findings do not support the notion that isokinetic hip abduction strength is correlated
with knee kinematics in healthy novice runners. Hip adduction strength was associated
with several frontal plane ankle kinematics in both male (initial contact angle: r = -
0.650, p = 0.002; toe-off angle: r = -0.534, p = 0.015; maximum angle: r = -0.546, p =
0.013; minimum angle: r = -0.710, p =< 0.001) and female novice runners (toe-off
angle: r = -0.710, p = <0.001; minimum angle: r = -0.517, p = 0.020; range of motion
(ROM): r = 0.579; p = 0.007). Additionally, knee flexion strength was associated with
greater knee adduction in the male runners (initial contact angle: r = 0.486, p = 0.030;
toe-off angle: r = 0.571, p = 0.008; maximum angle: r = 0.564, p = 0.010; minimum
angle: r = 0.459, p = 0.042), as well as a larger peak knee flexion angle (r = 0.617, p =
0.004) and increased sagittal plane ankle ROM (r = 0.465, p = 0.039) in the female
runners. Furthermore, concentric ankle strength exhibited several significant
correlations with running kinematics at the hip, knee and ankle in novice runners.
DISCUSSION. Male and female novice runners displayed distinct associations between
lower-limb strength and running kinematics. Several significant correlations were
identified between lower-limb isokinetic strength and injury-related kinematic
parameters. Additionally, the findings suggest that strengthening the muscles of the foot
and ankle, which has been shown to reduce RRIs, may also impact joint mechanics
higher up the kinematic chain. Further research is needed to validate these results and
assess the efficacy of lower-limb strengthening in altering running kinematics and
mitigating the risk of RRIs.
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