Over the past 35 years, several biomechanical modelling approaches have evolved and have been used to integrate our knowledge of how various biomechanical factors interact and their effects on tissue and subsequently movement. In order to analyse complicated movements and to find dominate factors, it seems inevitable to simplify the movements. Such a simplification is the biomechanical modelling of a movement.
Observing human responses and assessing ability for example in sportspeople completing drop jumps, can provide the athlete and coach plenty of information on perhaps acute power ability or response to an intervention. However in recent years biomechanics has delved further into the mechanisms underlying movement, using e.g. wireless EMG, neuromuscular response and joint coordination, advanced analysis like Principal Component Analysis (PCA), and musculoskeletal computer modelling. Figure 1: Sprinter Leg Model.
We Model to:
- Simplify the research question
- Reduce experimental inaccuracy
- Save time and costs associated with laboratory experimentation
- Isolate parameters, such as a part of the body for analysis
- By-pass ethical and injury problems associated with some experimentation such as falls research
- Validate any previous experimental data
Figure 2: Sprinter leg muscle force vectors
What Have We Studied?
Sprinting: Along with Professor Drew Harrison in 2010, I developed a computer model to examine the musculature of the hamstrings during sprinting. Figure 2 gif is a vector representation of the leg muscles during maximal sprinting. The larger the size of the muscle, the more force it is generating. We found the hamstrings to be very quiet during all but the final eccentric stretching phase of the leg swing, just as the athlete has ground contact. While we are still researching this with wireless EMG experimentation, the hamstrings seem to play a much smaller role than previously thought!
Golf: One of the most simple yet frustratingly difficult sports movements is the golf swing. I have modelled and created ‘Bob’ (Figure 3) which was work for the R&A Rules Ltd. St Andrews, to examine the physical effects of playing golf with drivers that are longer than the 48” (1.22 m) rule. Golf course experimentation showed that skilled (<5 handicap) golfers were able to hit longer and still maintain accuracy even using 50” (1.27 m) and 52” (1.32 m) drivers, but Bob showed that the muscle force and joint torque required had to increase by over 400% in the quadriceps and trunk to gain these shot benefits. Over a round of 18 holes, or competition of 72 holes this sustained effort would likely create fatigue very quickly. Figure 3: Golfer Long Club Musculoskeletal Model
Development: Figure 4 shows the development process of creating a human and equipment model. a)create the body segments you wish to study, b)add joints defining the body degrees-of-freedom and flexibility, c)add background inertial parameters (mass) to each segment based on the mass of your athlete, d)add skeletal structure, e)add soft tissues of known resting length and cross-sectional area, f)add an environment and connect such as feet to the ground, g)add contacts to measure ground reaction force, h)build and add any equipment such as metal properties for a golf club.
Previously collected 3D kinematics data of the athlete moving in a laboratory is then added to the static computer model and via inverse dynamics we can create a kinetic profile and move the model.
Figure 4. Golfer musculoskeletal computer model development
Applications: PhD researchers Niamh Whelan and Richie Bolger (who both recently passed their viva voce!) have used these models to further examine the deep lying musculature during sprinting drills and maximal velocity sprinting respectively. Deep muscles are difficult to examine experimentally so the modelling work will hopefully give us and athletes and coaches some insights into the role of smaller muscles and target training modalities.
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Dr Ian Kenny is a Lecturer in biomechanics, functional anatomy and research 
methods in the Department of Physical Education and Sport Sciences at the University of Limerick. He also works within the Biomechanics Research Unit (BRU) in his specialist area of applied sports biomechanics and musculoskeletal modelling. Contact details: ian.kenny@ul.ie View Ian’s profile here or on Research Gate.
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