Biomechanics experts gathering at Calgary International Society of Biomechanics Conference (Part 2/2)
I recently attended the International Society of Biomechanics Conference in Calgary. This conference gathers biomechanical scientific experts across a range of areas. I attended most of the running sessions. Here are interesting citations and key results from the speakers. Note that The Running Clinic and myself do not necessarily agree with all of these!
23. Goodwin J – Neuromechanical contributions to lower extremity stiffness differ between single leg hopping and running
Leg stiffness during hopping and running are not the same. Ankle muscles regulate leg stiffness during hoping and knee muscles regulate leg stiffness during running. There are step-to-step bimodal variations in stiffness during running.
24. Tacca J – How do prosthetic stiffness and running speed affect the biomechanics and symmetry of sprinters with unilateral transtibial amputations?
Running faster or with a stiffer prosthesis than recommended do not influence step symmetry in sprinters with unilateral trans-tibial amputations; but running with a more compliant prosthesis than recommended leads to asymmetric contact times.
25. Khassetarash A – Lower-extremity joint quasi-stiffness in graded running
Ankle stiffness is reduced during downhill running and energy is absorbed at the ankle. Knee stiffness is increased during uphill running due to the lesser energy absorption demands. Runners modulate lower-extremity stiffness during graded running.
26. Allen S – Biomechanics predict changes in metabolic cost during running and hopping at different frequencies
Rate of force production (c.-à-d., contact time) and active muscle volume predict metabolic power (Watt/kg) during running and hopping better than ground contact time alone.
27. Day E – Mechanics of the metatarsophalangeal and ankle joints and running economy do not change in response to increased isometric toe-flexor strength
An intrinsic foot muscle strength programme over 10 weeks increases intrinsic foot muscle strength, but did not change gait mechanics or metatarsophalangeal (big toe) mechanics or metabolic cost of running.
28. Pain M – Energy dissipation due to soft tissue movement of the shank during forefoot and rearfoot impacts at different running velocities
Energy dissipation due to soft tissue movement during running increases with running speed and with a rearfoot strike.
29. Forrester S – Principal component analysis of the relationship between running technique and economy
Principal component analysis on 153 runners – Good running economy in males linked with: smaller vertical pelvis motion, smaller hip motion during swing, smaller peak knee flexion during stance and swing. Good running economy in females linked with: smaller axial rotation, less plantar-flexion at toe-off, earlier peak abduction during stance, and more neutral ankle during early swing. Pelvis measures were correlated at all speeds, but hip and knee measures were not at faster speeds. Take home message: economical runners have smaller range of motion and differences between males and females exist.
30. Copriviza C – Effects of manipulating center of mass vertical motion on running economy
Runners ran at 0 – 75 – 100 – 125 – 150% of their habitual centre of mass vertical motion at 2.7 m/s. Metabolic power (Watt/kg) was 27% increased at 150% of habitual centre of mass vertical motion. Centre of mass motion and ground contact time accounted for 49% and 16% of the variance in metabolic power, respectively. Stride length, contact time, and peak knee flexion increased with centre of mass movement. Biceps femoris, vastus lateralis, and tibialis anterior activation increased at lower centre of mass movement. Running economy is optimized at 6 to 8 cm of vertical motion.
RUNNING BIOMECHANICS: FOOT STRIKE PATTERN
31. Mahoney J – Footstrike pattern recognition using machine learning on tibial accelerometry
Machine learning techniques show promising results for detecting foot strike pattern from accelerometers placed on the tibia. Neural networks outperformed Support Vector Machines.
32. Swinnen W – Triceps surae metabolic energy consumption in rearfoot and mid-/forefoot strikers
There was no difference in triceps surae energy consumption between foot strike patterns or triceps surae metabolic energy consumption in relation to whole body energy consumption, regardless of the model used.
33. Lin-Wei Chen T – Shear wave velocity in the plantar fascia of runners using different foot strike techniques
Plantar fascia thickness and echogenicity did not differ between rearfoot and forefoot strikers using B Mode ultrasound imaging, but plantar fascia shear wave velocity was slower in forefoot strikers using elastographic ultrasound imaging. Findings indicate that forefoot strikers had a less elastic plantar fascia than rearfoot strikers. Reduced elasticity leads to increased strain and could cause plantar fascia injuries in forefoot runners. Foot strike pattern modification in runners should be accompanied by a strengthening program.
34. Cheung R – Can impact sound amplitude and frequency differentiate footstrike patterns?
There is < 1 % chance for runners to remain injury free across 3 years mathematically. Footfall sounds were quieter (sound amplitude) when rearfoot striking than non-rearfoot striking. The pitch (sound frequency) was lowest when rearfoot striking and highest when midfoot striking. There was no relationship between sound and vertical loading rates.
FOCUS ON FEMALE RUNNERS
35. Gruber A – Run like a woman: the biomechanics of female runners
78% of studies do not consider sex differences in running-based injuries.
36. Milner C – Impact loading and tibial stress fracture in female runners
Peak tibial axial acceleration while running outdoors (grass and sidewalk) was almost 2 times higher than running in the lab (treadmill and lab floor) at the same running speed and cadence. We need to measure in the field rather than in the lab and start measuring new associations with tibial stress fractures.
37. Steele J – Run like a woman: frictional bra-breast injuries in running
Frictional bra injuries in female runners happen often and can have a negative effect on sporting performance, but these are not often reported by athletes. Website: www.bra.edu.au/sportsbra
38. Moore I – Economical running biomechanics in female runners
The running technique used by females is not merely a scaled down version of the male model (Nelson 1977). Metabolically, co-activation is costly. Greater leg flexion at push-off is economical for female runners (c.-à-d., less plantar-flexion, more hip/knee flexion).
39. Azevedo A – Gender responses to minimal running: preliminary results about interest, participation and training effects
There are a lower number of female than male runners who have tried minimal shoe running. Following a 12-week barefoot running interval training, biomechanical habituation between males and females were different. Females reduced impact peak in both barefoot and standard shoes, but reductions in males were seen in barefoot only.
40. Boyer K – Running through the lifespan: benefits and risks for female athletes
Benefits of running in midlife may be greatest for women – i.e., consequences from non-running and declines in neuromuscular function are greater in women than men. Take home: aging is not impacting men and women in the same way.
41. Agresta C – Female runners reduce proximal segment motion and alter stride dynamics postpartum
Women running at 6-weeks postpartum versus pre or early pregnancy demonstrate reduced trunk flexion and excursion, reduced trunk and pelvis rotational excursions, and increased foot size. Postpartum, there is a change in type and motivation for running.
42. Snyder K – Atalantas assemble: can the women's marathon world record be broken under an optimal cooperative drafting strategy?
Breaking the current world record set by Paula Radcliffe (2:15:25) would be possible with cooperative drafting of four elite female runners based on modelling approaches. Note : the record was broken by Brigid Kosgei in Chicago on October 13, 2019 (2:14.04).
43. Saxton J – Gender differences of joint coordination and kinetics in healthy runners
Joint coupling and kinetic variables were similar between males and females running on the treadmill.
44. Benson L – Greater medial-lateral regularity for treadmill vs. outdoor running observed in males but not females
The regularity of anterior-posterior and vertical accelerometer signals is higher during treadmill than sidewalk running. There is greater side-to-side consistency in accelerometer signals in females than males during both treadmill and sidewalk running. Side-to-side consistency in males was greater on the treadmill than on the sidewalk.
45. Garcia M – Does gender relate to lower limb asymmetry in adolescent long-distance runners?
Adolescent long-distance female runners showed greater lower-extremity kinematic asymmetry than males in sagittal knee and coronal ankle position. There was high variability in side-to-side symmetry overall.
46. Allen S – Differences in running technique between males and females
Stride rate, stride length, and stride time were different between males and females (matched for performance and running economy) when non-normalised to leg length, but duty factor was similar. There were several other kinematic differences – females showed greater knee flexion immediately prior to stance, hip adduction during late swing and stance, hip abduction during swing, hip internal rotation at toe-off, knee abduction during stance, ankle eversion during stance, and axial rotation of the torso; and less dorsiflexion during stance. Kinematic differences may have implications for footwear design, performance enhancements, and injury prevention.