Is Motorized Treadmill Running Biomechanically Comparable to Overground Running? A Systematic Review and Meta-Analysis of Cross-Over Studies

Abstract

Background: 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.

Methods: Four 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.

Results: 33 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.

Conclusions: Spatiotemporal, 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).

Fig. 1

Literature search flow chart. n number of studies

Fig. 2

Risk of bias assessment for all included studies

Fig. 3

Random-effects meta-analysis of ground contact time during MT compared to overground running. Subgroup analysis based on overground surface with subgroups organized from least stiff surface to stiffest surface and studies organized from slowest to fastest speed. CI confidence interval, df degrees of freedom, MD mean difference, N sample size

Fig. 4

Random-effects meta-regression of contact time during MT compared with overground running based on running speed. Larger data points received greater weighting than smaller data points. Solid lines represent the estimated relationship and dashed lines represent the upper and lower 95% confidence limits

Fig. 5

Random-effects meta-analysis of a sagittal foot–ground angle at footstrike, b knee flexion angle at footstrike and c knee flexion range of motion from footstrike to peak during stance during MT compared to overground running. Subgroup analysis based on overground surface with subgroups organized from least stiff surface to stiffest surface and studies organized from slowest to fastest speed. CI confidence interval, df degrees of freedom, MD mean difference, N sample size

Fig. 6

Random-effects meta-analysis of vertical displacement during MT compared to overground running. Subgroup analysis based on overground surface with subgroups organized from least stiff surface to stiffest surface and studies organized from slowest to fastest speed. CI confidence interval, df degrees of freedom, MD mean difference, N sample size

Fig. 7

Summary of significant differences between treadmill and overground running biomechanics found with meta-analyses. Overall surface effects are indicated in black, subgroup (individual surface) effects in gray. Amplitude of muscle activity represents a qualitative interpretation of the findings as meta-analysis could not be performed for this outcome. ROM range of motion. Treadmill; “down arrow” lower; “up arrow”, greater/longer compared to overground