One of the determining factors of running performance is running economy (RE), and modifiable running biomechanics are a determining factor of RE. This review examined the intrinsic and extrinsic modifiable biomechanical factors affecting RE, assessed training-induced changes in RE and running biomechanics, evaluated whether an economical running technique can be recommended, and discussed potential areas for future research directions.
Modifiable running biomechanical factors that affect RE include spatiotemporal factors, lower limb kinematics, kinetics, neuromuscular factors, shoe–surface interactions, and trunk and upper limb biomechanics.
Based on current evidence, the intrinsic factors that appeared beneficial for RE are a self-selected stride length with a 3% shorter stride length range, lower vertical oscillation, greater leg stiffness, low lower limb moment of inertia, alignment of the GRF and leg axis vectors, less leg extension at toe-off, larger stride angles, maintaining arm swing, low muscle activation during propulsion, and low antagonist–agonist thigh co-activation.
In regards to extrinsic factors, better RE was found to be associated with a firm, compliant shoe-surface interaction and being barefoot or wearing lightweight shoes.
Several other modifiable biomechanical factors presented inconsistent relationships with RE. These biomechanical factors include ground contact time, impact force, anterior–posterior forces, trunk lean, lower limb biarticular muscle co-activation, and orthotics, presented inconsistent relationships with RE.
Collectively, the evidence shows that running biomechanics during ground contact, particularly those related to propulsion, such as less leg extension at toe-off, larger stride angles, alignment of the ground reaction force and leg axis, and low activation of the lower limb muscles, appear to have the strongest direct links with running economy.
Inconsistent findings and limited understanding still exist for several spatiotemporal, kinematic, kinetic, and neuromuscular factors and how they relate to running economy. Recurring methodological problems exist within the literature, such as cross-comparisons, assessing variables in isolation, and acute to short-term interventions. Further, intra-individual differences due to unmodifiable factors limit the findings of cross-comparisons. Therefore, recommending a general economical running technique should be approached with caution.
Future research work within the field should focus on a synergistic approach to assessing kinetics as well as integrated approaches combining VO2, kinematics, kinetics, and neuromuscular and anatomical aspects to increase our understanding of economical running technique. Runners should be assessed on an individual basis.