Keynote Lectures

Estimating Bone Loading During Physical Activity: Where Do We Go Next?
Hannah Rice, Norwegian School of Sport Sciences, Norway, Norway

Reconsidering Energy Sources and Destinations in Sport Activities
Alberto Minetti, University of Milan, Italy, Italy

Abstract
Bone stress injuries affect athletic populations who undertake activities in which bones are repeatedly loaded. In order to understand and reduce the risk of bone stress injuries, we need to quantify the loading experienced by the bones during activities such as running. Bone loading is difficult to quantify as the magnitudes of stress are influenced to a large extent by the magnitude of muscular forces acting on the bone. Musculoskeletal modelling, ranging from very simple to very complex approaches, can be used to estimate the internal loading experienced by the bone during human movement such as running. This has allowed us to explore factors such as speed, slope, step width and step length and their influence on bone loading during running. However, in order to truly understand risk of stress injuries this needs to be taken out of the lab and in-field. Today we have access to rapidly improving technology and data processing capabilities. Could this facilitate the estimation of bone loading in real time? This talk will consider the current limitations and challenges, and how might these be overcome in the future.

Abstract
The speech will focus on 4 main topics, chosen as to stress the importance of a combined biomechanical and physiological approach, together with modern sensory technology, to highlight the relevant energy sources in sport movement and locomotion:
a) Downhill skiing is by definition an activity transforming the vertical body position (i.e. potential energy)  into movement (e.g. speed, or kinetic energy). Which contraction type is mainly expected from our muscles? 
b) Standing long jump dates since a few centuries BCE. Fifty years before being reissued in early XX century Olympics, British jumpers (over canals) used, similarly to ancient Greek Pentathletes, to swing dumbells before taking off. Some of them also throwed the loads backward-downward during midflight to achieve extra propulsion, as (indipendently) studied by rocket scientists of that time. What was the catch?
c) Among the components of internal mechanical work, the one due to body segments acceleration has been classically put into focus, though how this complements the external work is still under debate. Recent attention has been paid to internal frictonal work (dissipation), which naturally slows down passive and active oscillations of segments.
d) Why don’t we still have a reliable equation predicting the metabolic power of cycling? The internal mechanical work (kinematic and frictional) and muscle efficiency as a function of pedalling rate can help to fill the gap.

Bibliography
1. Minetti A. E. Concentric, isometric and eccentric contractions: which dominates alpine skiing?. Science and Skiing VII, E. Müller, J. Kröll, S. Lindinger, J. Pfusterschmied, J. Spörri, T. Stöggl Eds, Meyer & Meyer Sport (UK), pp 23-29, 2018.
2. Minetti A. E. and Ardigó L. 19th century jumpers reinvented halteres and extended Olympians' range by ante litteram rocket propulsion. Latin American Crosstalk in Biophysics and Physiology, Salto Grande, Uruguay 2015.
3.    Minetti A. E., Moorhead A. and G. Pavei. Frictional internal work of damped limbs oscillation in human locomotion. Proc. R. Soc. B, http://doi.org/10.1098/rspb.2020.1410 Suppl.Material, 2020.
4. Minetti, A. E. The role of negative external and positive internal mechanical work in human locomotion energetics. VIIth World Congress of Biomechanics, Boston, July 6-11th 2014.