We’re always keen to provide runners with the best opportunity to understand more about running and specifically how runners run. We love using technology and combined with assessment this works well for helping runners to get over injury and improve performance. As a team of techno geeks, imagine our delight when we got our hands on DorsaVi. A wearable device that runners or teams can use to monitor kinetic running data & kinematic knee data to understand the loads and biomechanics of the athlete.
Wearable devices have been used for several years in sport specifically HR monitors & GPS trackers used to monitor load, distance and intensity of players, both in training and competition situations. Even though new evidence is being published to help us understand that training loads are one factor linked to injury, this study from expert Gabbett is particularly comprehensive [Gabbett. 2007].
It’s become more complex to measure biomechanics in the field of play because we need 3D motion capture to fully assess motion in team sports, which is unpredictable in many team sports [Willy, 2017]. The assessment of biomechanics in runners within any sporting environment is extremely difficult, hence the advent of such technologies that help assess movement naturally are welcomed by us.
What we we look for?
Ground Reaction Force [GRF] – The force created by contact with the ground is referred to as the ground reaction force (GRF). This is the force the ground exerts on the body as we move. According to Newton, for every action there is an equal and opposite reaction [Newton’s 3rd Law of Motion – Law of Reaction]. As we make contact with the ground, gravity is constantly impacting the body [Young-Hoo Kwon, 1998: http://www.kwon3d.com/theory/grf/grf.html].
Initial Peak Acceleration [IPA] – Correlates the vertical acceleration and loading rate through the tibia on ground contact, measured in G’s. The IPA being increased has been linked to higher rates of stress fractures [Crowell, 2011] and changes can be noted with alterations in cadence [Rios et al, 2010]. This graph illustrates these measurements nicely [DorsaVi ViMove2, Running Module Guide].
Cadence calculates steps per minute, two steps make up one stride. Recent research indicates shortening stride length and increases in cadence can help to reduce running injuries [https://www.runresearchjunkie.com/is-the-180-cadence-a-myth-or-something-to-aim-for/].
Absolute Symmetry Index [ASI] – is the calculation of average GRF Left vs Right. An example in DorsaVi would be a negative value indicates the right side is carrying more force compared to left. A positive values shows left side is accepting more force than the right side. A normal deviation in ASI is 5% so we would want to reduce this whilst running [Herzog et al, 1989].
Speed – Looks at average speed over the course of the running time measured, usually measured in metres per second [m/s].
Everybody runs differently and this is dependent on multiple factors including:
1. Activity participation [distance runners, sprinters, team sports]
2. Running surface, environment & terrain [surface type, inclination, weather]
3. Running footwear
4. Position within a team or squad [defender Vs attacker]
5. Level of activity participation [elite Vs recreational]
What happens when these factors change?
Sports physio Paddy volunteered to test out the DorsaVi. We looked at his existing running style and implemented changes in order to measure the differences in kinetics data.
Within 15 minutes, we were able to assess Paddy clinically and on the treadmill. We looked at Paddy running at 9km/hr, 12km/hr & 16 km/hr. At each assessment, Paddy changed something in his gait to see what changes we noted in his kinetic data. The difficult question is, does kinetic data correlate to kinematics?
As the overview graph illustrates, Paddy completed 3 runs at 9 km/hr but what we can’t see from the graph is what kinematics changed.
- Rep 1 at 9 km/hr Paddy was running his normal gait pattern with no problems reported.
- Rep 2 at 9 km/hr Paddy changed his foot strike pattern which resulted in a reduction in cadence
- Rep 3 at 9 km/hr paddy attempted to shorten stride length and increase cadence
- Rep 4 at 12 km/hr increased speed which initially he achieved by increasing his cadence
- Rep 5 at 12 km/hr Paddy maintained his speed and his cadence settled to 173.
- Rep 6 at 16 km/hr we noted a huge ASI change which correlates to a previous lower limb injury Paddy has suffered on his right side. Increased IPA & GRF despite GCT becoming more symmetrical compared to previous speeds.
Overall, the DorsaVi running module kit is a game changer for us. It is portable and ease of use on the iPad. I would recommend it as suitable for all types, levels and style of runners. We only explored the running module in this article but the knee and lumbar spine assessment modules are great additions to any clinical assessment. The smart therapist would with clinical information, training information along with goal setting to get results with patients and athletes. The versatility of DorsaVi means its suitable for everyone not just sports people.
I’m yet to see any normal data ranges for athletes with GRF, IPA and GCT but differences in assessment and correlation can lead us to make assumptions – if the data supports the hypothesis of injury, then it can be used to change running gait, ultimately reduce pain and improve performance.
However, one question remains in my mind which I’ve not seen in research yet – Does kinetic data correlate to kinematics?
Thanks for reading.
Gabbett & Domrow. (2007). Relationships between training load, injury, and fitness in sub-elite collision sport athletes. Journal of sports sciences. 25. 1507-19. 10.1080/02640410701215066.
Young-Hoo Kwon. (1998). Webite: http://www.kwon3d.com/theory/grf/grf.html. Accessed December 2017
Harrison Philip Crowell and Irene S. Davis. (2011). Gait Retraining to Reduce Lower Extremity Loading in Runners. Clin Biomech (Bristol, Avon). 2011 Jan; 26(1): 78–83.
Jaqueline Lourdes Rios, Mário Cesar de Andrade, Aluisio Otavio Vargas Avila. Analysis of Peak Tibial Acceleration During Gait in Different Cadences. Human Movement 2, December 1, 2010.
Herzog, Nigg, Read, Olson . (1989). Asymmetries in group reaction force patterns in normal human gait. Med Sci Sports Exerc; 21: 110–114
Baggaley, Willy, Meardon. (2017). Primary and secondary effects of real‐time feedback to reduce vertical loading rate during running. Scandinavian journal of medicine & science in sports 27 (5), 501-507