The sensible running technique coaches that I listen to often talk about the forward lean from the ankle when running rather than a forward lean at the hips. Ironically, the fan boys from the various running form cults also often say the same thing, so there must be something to it. I have certainly tried to focus on this to some extent in my own running as the rationale behind it did make some sense. While delving into some of the proximal control issues associated with running technique is somewhat out of my area of expertise, this new study did catch my eye:
Influence of Trunk Posture on Lower Extremity Energetics during Running.
Teng, Hsiang-Ling; Powers, Christopher M
Medicine & Science in Sports & Exercise: July 8, 2014
Purpose: To examine the influence of sagittal plane trunk posture on lower extremity energetics during running.
Methods: Forty asymptomatic recreational runners (20 males, 20 females) ran overground at a speed of 3.4 m/s. Sagittal plane trunk kinematics and lower extremity kinematics and energetics during the stance phase of running were computed. Subjects were dichotomized into High-Flexion (HF) and Low-Flexion (LF) groups based on the mean trunk flexion angle.
Results: The mean (+/-SD) trunk flexion angles of the HF and LF groups were 10.8[degrees] +/- 2.2[degrees] and 3.6[degrees] +/- 2.8[degrees], respectively. When compared to the LF group, the HF group demonstrated significantly higher hip extensor energy generation (0.12 +/- 0.06 J/kg vs. 0.05 +/- 0.04 J/kg, p<0.001) and lower knee extensor energy absorption (0.60 +/- 0.14 J/kg vs. 0.74 +/- 0.09 J/kg, p=0.001) and generation (0.30 +/- 0.05 J/kg vs. 0.34 +/- 0.06 J/kg, p=0.02). There was no significant group difference for the ankle plantar flexor energy absorption or generation (p>0.05).
Conclucion: Sagittal plane trunk flexion has a significant influence on hip and knee energetics during running. Increasing forward trunk lean during running may be utilized as a strategy to reduce knee loading without increasing the biomechanical demand at the ankle plantar flexors.
What this study showed is that more of a forward lean of the trunk at the hips resulted in less knee loads, greater hip loads and no effect on ankle loads. The small difference in forward lean (flexion angle) did lead to a relatively large differences in knee loads which has the potential to help those with problems related to knee loads, but in my limited understanding of good running form, that this may not be what many would consider good running form.
Nothing in the study jumped out at me as an issue with the methods, analysis and interpretation except for I am a little perplexed as to why they analysed the data the way they did. There was no rationale given for it in the paper. They divided the participants into two groups (high and low flexion) and looked at the different parameters between the two groups. I don’t necessarily have a problem with that and just wonder why they did not do a simple correlation between the trunk flexion angle and each parameter measured.
This paragraph in the discussion really struck a chord:
Modification of the foot strike pattern has been advocated as a means to reduce the risk of lower extremity injuries during running. For example, converting a rearfoot strike pattern to a midfoot or forefoot strike pattern has been shown to result in a significant reduction in the knee extensor moments, power, and energy absorption.(1,16,39) Furthermore, barefoot running, which typically results in a midfoot or forefoot strike pattern,(24) has been promoted to reduce knee joint loading.(4,5,39) However, studies have reported that adopting a midfoot or forefoot strike pattern also leads to significant increases in ankle plantar flexor moments, power and energy absorption.(1,4,6,16,28,29,39) Bonacci et al.(4) reported that converting runners from shod to barefoot running resulted in a 23.7% reduction in knee energy absorption and a 23.8% increase in ankle energy generation. Moreover, Williams et al.(39) reported that a forefoot strike pattern led to a decrease in knee negative power and a corresponding increase in ankle negative power when compared to a rearfoot strike pattern.
Taken together, current running literature suggests that converting to a midfoot or forefoot strike pattern reduces knee loading during running by shifting the mechanical demand to the ankle joint. This is potentially problematic, as the ankle joint normally absorbs and generates 40%-50% of the total energy in the lower extremity during running.(11, 19) Shifting the mechanical demand to the calf musculature may lead to increased potential for foot and ankle injuries, which has been observed in persons who are habitual midfoot or forefoot strikers.
Which is a another way of saying if you change the way you run to decrease the load in one tissue, you increase it in another. The authors offer the results of their study (ie increased forward lean at the hip) as a way to reduce knee loads without increasing ankle loads. This does, however, come at the cost of increasing hip loads. I guess it all comes down to which is the tissue that there is a problem with and can the tissue that you move the load to take it. This does run somewhat contrary to the recommendations of not leaning forward at the hip and lean forward from the ankles when running.
As always, I go where the evidence takes me until convinced otherwise and this just adds to the: Different Running Techniques Load Different Tissues Differently
Teng, H., & Powers, C. (2014). Influence of Trunk Posture on Lower Extremity Energetics during Running Medicine & Science in Sports & Exercise DOI: 10.1249/MSS.0000000000000436