The effect of forward postural lean on running economy, kinematics, and muscle activation

Abstract

Background: Running economy, commonly defined as the metabolic energy demand for a given submaximal running speed, is strongly associated with distance running performance. It is commonly believed among running coaches and runners that running with increased forward postural lean either from the ankle or waist improves running economy. However, recent biomechanical research suggests using a large forward postural lean during running may impair running economy due to increased demand on the leg muscles.

Purpose: This study tests the effect of altering forward postural lean and lean strategy on running economy, kinematics, and muscle activity.

Methods: 16 healthy young adult runners (23±5 years, 8M/8F) ran on a motorized treadmill at 3.58m/s using three postural lean angles [upright, moderate lean (50% of maximal lean angle), and maximal lean] and two strategies (lean from ankle and lean from waist [trunk lean]). Metabolic energy consumption, leg kinematics, and muscle activation data were recorded for all trials.

Results: Regardless of lean strategy, running with an increased forward postural lean (up to 8±2 degrees) increased metabolic cost (worsened economy) by 8% (p < .001), increased hip flexion (p < .001), and increased gluteus maximus (p = .016) and biceps femoris (p = .02) muscle activation during the stance phase. This relation between running economy and postural lean angle was similar between the ankle and trunk lean strategies (p = .743).

Conclusion: Running with a large forward postural lean reduced running economy and increased reliance on less efficient extensor leg muscles. In contrast, running with a more upright or moderate forward postural lean may be more energetically optimal, and lead to improved running performance.

Fig 1

Image of running with ankle (A) and torso (B) postural lean strategy. Solid line represents total postural lean angle and hatched (—-) line represents the torso flexion angle. Images shown here are similar to the sagittal view video feedback used for the prescribed moderate and maximal lean trials. Participants were asked to maintain the prescribed postural lean angle throughout the trial using the prescribed lean strategy (ankle or torso).

Fig 2. Mean (± SE) net metabolic power (Watt·kg^-1) plotted as a function of postural lean angle for runners using no lean (⬖), ankle strategy (●), and torso strategy (▽).

Asterisks (*) indicate significant differences from both no lean and moderate lean running (p < .05). Net metabolic cost increased with lean angle yet there was no significant difference in metabolic power between postural lean strategies (p = .700).

Fig 3. Mean (±SE) peak hip flexion angle (°) during the stance phase plotted as a function of postural lean angle for runners using no lean (⬖), ankle strategy (●) and torso strategy (▽).

Asterisks (*) indicate significant differences from both no lean and moderate lean angles (p < .05). Peak hip flexion angle increased with lean angle yet there was no significant difference in peak hip flexion angle between postural lean strategies (p = .570).

Fig 4

Average normalized EMG_RMS signals of the (A) gluteus maximus, (B) biceps femoris, (C) rectus femoris, and (D) vastus medialis muscles for the no lean (0 deg, ⬖), moderate lean (4.3 deg, ⬜), and large lean (8.3 deg, ⬤) conditions over a complete stride (0–100% of gait cycle). Each data point represents the average of ankle and torso lean strategies. Tibialis Anterior, Soleus, and Medial gastrocnemius activity exhibited no significant effects of lean angle or lean strategy, and thus are not shown. Asterisks (*) indicate significant differences from the large postural lean condition (p < .05).