Abstract
BackgroundTreadmills are often used in research, clinical practice, and training. Biomechanical investigations comparing treadmill and overground running report inconsistent findings.ObjectiveThis study aimed at comparing biomechanical outcomes between motorized treadmill and overground running.MethodsFour databases were searched until June 2019. Crossover design studies comparing lower limb biomechanics during non-inclined, non-cushioned, quasi-constant-velocity motorized treadmill running with overground running in healthy humans (18–65 years) and written in English were included. Meta-analyses and meta-regressions were performed where possible.Results33 studies (n = 494 participants) were included. Most outcomes did not differ between running conditions. However, during treadmill running, sagittal foot–ground angle at footstrike (mean difference (MD) − 9.8° [95% confidence interval: − 13.1 to − 6.6]; low GRADE evidence), knee flexion range of motion from footstrike to peak during stance (MD 6.3° [4.5 to 8.2]; low), vertical displacement center of mass/pelvis (MD − 1.5 cm [− 2.7 to − 0.8]; low), and peak propulsive force (MD − 0.04 body weights [− 0.06 to − 0.02]; very low) were lower, while contact time (MD 5.0 ms [0.5 to 9.5]; low), knee flexion at footstrike (MD − 2.3° [− 3.6 to − 1.1]; low), and ankle sagittal plane internal joint moment (MD − 0.4 Nm/kg [− 0.7 to − 0.2]; low) were longer/higher, when pooled across overground surfaces. Conflicting findings were reported for amplitude of muscle activity.ConclusionsSpatiotemporal, kinematic, kinetic, muscle activity, and muscle–tendon outcome measures are largely comparable between motorized treadmill and overground running. Considerations should, however, particularly be given to sagittal plane kinematic differences at footstrike when extrapolating treadmill running biomechanics to overground running. Protocol registration CRD42018083906 (PROSPERO International Prospective Register of Systematic Reviews).
Highlights
Motorized treadmills (MT) are often used for research, clinical practice, and training purposes
Of the 33 included studies, 16 included males only, 15 a mix of males and females and two did not specify gender. 30 studies recruited participants that were runners or physically active in other sports, and three studies did not specify the physical activity of the participants. 21 studies further specified that the participants had prior experience with MT running, while this information was unclear in other studies. 23 studies specified the motor power and belt dimensions, or provided enough data to gather this information
A reduced vertical displacement will require less acceleration in the vertical direction, and it follows from Newton’s second law; force = mass × acceleration, that this reduced vertical acceleration will reduce total vertical forces when body mass remains equal. These lower forces in turn require less muscle activation. These findings collectively indicate that the majority of electromyography outcome measures do not significantly differ between MT and overground running, and that some muscles are activated to a lower extent during MT compared to overground running
Summary
Motorized treadmills (MT) are often used for research, clinical practice, and training purposes. Extended author information available on the last page of the article is increasingly combined with video analysis to investigate running technique and inform footwear, orthotic, and gait retraining strategies for performance enhancement, injury prevention and rehabilitation [3–5]. Treadmills are often used in research, clinical practice, and training. Biomechanical investigations comparing treadmill and overground running report inconsistent findings. Objective This study aimed at comparing biomechanical outcomes between motorized treadmill and overground running. Crossover design studies comparing lower limb biomechanics during non-inclined, non-cushioned, quasi-constant-velocity motorized treadmill running with overground running in healthy humans (18–65 years) and written in English were included. Conclusions Spatiotemporal, kinematic, kinetic, muscle activity, and muscle–tendon outcome measures are largely comparable between motorized treadmill and overground running. Protocol registration CRD42018083906 (PROSPERO International Prospective Register of Systematic Reviews)
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