Download article as pdf

The School of Sport Science, Exercise and Health (SSEH) at the University of Western Australia (UWA) currently run two motion analysis laboratories, a 12 camera Vicon MX system for sports research, and a 7 camera Vicon MX motion analysis system for clinical research. The UWA group has always been heavily involved in sports and clinical biomechanics research, but now a team of researchers (Drs. Jonas Rubenson, David Lloyd and Paul Fournier) have also branched into investigating the locomotion of birds to understand the principles of human bipedal locomotion. To study the mechanics and energetics of gait in the largest bird species, the ostrich (Struthio camelus), they implemented a range of techniques normally used in clinical gait analysis.

Initially, the team trained birds to walk and run on a treadmill, while collecting both metabolic (oxygen consumption) data and 2D kinematic data using high-speed video cameras. Subsequently, an outdoor gait laboratory was built (in collaboration with Denham Heliams and Fauna Technologies) that integrated kinematic data from Peak high-speed cameras and force-plate data using Vicon’s BodyBuilder software to analyze 3D joint biomechanics.

Their findings are providing insight into musculoskeletal form and function, as well as long-standing questions of bipedal gait. The team’s work has contributed to a shift in the way we interpret walking and running. Traditionally, running is distinguished from walking on the basis of having an aerial phase, i.e. when both feet are off the ground. However, they have shown that this definition of walking and running may be misleading [1]. An alternate definition of walking and running is based on mechanical energetics, walking being defined as a pendulum-like exchange between gravitational potential energy and horizontal kinetic energy, while running defined as a bouncing-like exchange of both gravitational and kinetic energy with the elastic energy stored in the legs. Their findings showed that bouncing running can occur without an aerial phase in ostriches, which the authors have called “grounded running”. It has now been speculated that humans may use grounded running when moving on very compliant surfaces or in altered gravity environments (such as those on other planets), and that some children with cerebral palsy are using a grounded running gait rather than a walking gait.

The study also found that the selection between walking and grounded running is associated with a reduction of the metabolic cost of locomotion in ostriches. This finding solidifies the view that energy use is a key factor dictating gait selection in animals, including humans. Importantly, the study shows that the shift in dynamics of the body probably explains the reduction in energy use when humans choose to switch to a run.

The researchers are further exploring the relationship between locomotor mechanics and energetics. Ostriches possess a strikingly different limb morphology compared to humans, yet share a similar body mass. Because of this, ostriches are an excellent comparative model for understanding the mechanical determinants of human locomotor energy use.

The first step in this research was the development of a 3D kinetic model of the ostrich limb. The model was constructed from both static anatomical data and joint motion data using the school’s Vicon motion capture system. The model has been used to explore whether mechanical and/or muscular work can explain the differences in the energy cost of locomotion between ostriches and humans. The investigators have also used their 3D model to explore the control of 3D joint and limb motions of running ostriches [2].

Ostriches may prove to be useful models for other areas of biomechanics. For example, these animals are capable of running and maneuvering at incredible speeds and, as the researchers have discovered, with remarkably high loads at their joints. Ostriches may yet reveal a few secrets of knee joint stabilization and injury prevention.

Preventing Sports Injury
Understanding knee joint loading and stabilization during running and sidestepping is a key to preventing anterior cruciate ligament (ACL) injuries in sport. These costly injuries occur all too often in many sports around the world, which is the reason for the large ACL injury research programme at UWA (Drs David Lloyd, Tim Doyle, Jacque Alderson, Profs Bruce Elliott and Tim Ackland, and PhD students Alasdair Dempsey, Jon Donnelly, James Dunne and Marcus Lee). The reason why the ACL ruptures is very simple: it breaks when the load applied to the ligament exceeds its’ current strength. However, this raises two much more difficult questions to answer. The first, why does the strength of the ligament get too low? The second, why does the load applied to ligament get too big? This latter question is the focus of the UWA research.

ACL ruptures most commonly occur just after initial foot contact during non-contact sidestepping [3-5]. The UWA group has shown that in this period of the sidestep the knee is loaded with large valgus and internal rotation moments, while the quadriceps are extending the knee [6-8]. However, there were no broken ACL’s in their laboratory studies. Reviewing videos of ACL injuries actually occurring has shown that when the ACL breaks the knee gives way into valgus and internal rotation [3-5]. So valgus and internal rotation moments, combined with the quadriceps extending the knee, all which highly loaded the ACL in cadaveric studies [9], are the probably loads causing ACL injury during sidesteps. To prevent ACL injuries from occurring external valgus and internal rotation moments need to be reduced. But there is another way to prevent injury. It appears the knee loads recorded during laboratory sidestepping were on many occasions larger than those required to completely break all the knee ligaments [10], not just the ACL. But people did not break their knee ligaments in the laboratory! This suggested to the UWA group that muscles stabilize the knee preventing ACL rupture [11, 12]. So to reduce the incidence of ACL injuries one must lower loading and/or improve the muscular stabilization of the knee in sidestepping [13].

The UWA group has engaged in two laboratory based training studies funded by the Australian Football League Research and Development Board. The findings revealed that while sidestepping, certain facets of the player’s technique can be changed to decrease knee loading. and that specially designed balance training will improve muscular stabilization of the knee. But does such training actually work to reduce ACL injury?

Some very good research from other groups has shown the promise of balance training [14, 15], but no work has addressed technique training. By teaming up with sports epidemiologist Professor Caroline Finch at University of Ballarat, the UWA group has received over $1,000,000 from the Australian National Health and Medical Foundation to see if their technique and balance training can reduce the incidence of ACL in community level Australian Football. This four year study is half completed and has shown some exciting data regarding this scientifically developed training.

Upper Limb Modelling and International Cricket Council
While this lower limb ACL injury research continues, the UWA group (Drs Yanxin Zhang, David Lloyd, Si Reid and Jacque Alderson, with PhD candidates Aaron Chin, Amity Campbell, and Kane Middleton) has been continually developing and testing new upper body motion analysis models.

The first upper limb model developed by the group was applied to “chucking in cricket bowling” [16]. The International Cricket Council is currently using the model in Biomechanics of Bowling testing unit [17]. Based on the experience gained from this work and the development of their lower body model [18], UWA is finishing the development of their “new” upper body model.

This new model uses multiple marker triads per segment, functional calibration methods and MRI imaging to best represent and measure torso, shoulder, elbow and wrist motion in many and varied upper limb tasks.

This very active group continues to develop innovative motion analysis modeling methods and apply them to movement research in sports performance, sports injury, comparative animal work, and clinical musculo-skeletal conditions.

References
1. Rubenson, J., B. D. Heliams, D. G. Lloyd, and P. A. Fournier. Gait selection in the ostrich: mechanical and metabolic characteristics of walking and running with and without an aerial phase. Proc. R. Soc. B. 2004;271:1091 - 1099.
2. Rubenson, J., T. F. Besier, B. D. Heliams, D. G. Lloyd, and P. A. Fournier. Running in ostriches (Struthio camelus): three-dimensional joint axes alignment and joint kinematics. J. Exp. Biol. 2007;210:2548-2562.
3. Boden, B. P., G. S. Dean, J. A. Feagin, Jr., and W. E. Garrett, Jr. Mechanisms of anterior cruciate ligament injury. Orthopedics. 2000;23:573-578.
4. Cochrane, J. L., D. G. Lloyd, A. Buttfield, H. Seward, and J. McGivern. Characteristics of anterior cruciate ligament injuries in Australian football. Journal of Science and Medicine in Sport. 2007;10:96-104.
5. Olsen, O. E., G. Myklebust, L. Engebretsen, and R. Bahr. Injury mechanisms for anterior cruciate ligament injuries in team handball: a systematic video analysis. Am J Sports Med. 2004;32:1002-1012.
6. Besier, T. F., D. G. Lloyd, T. R. Ackland, and J. L. Cochrane. Anticipatory effects on knee joint loading during running and cutting maneuvers. Med Sci Sports Exerc. 2001;33:1176-1181.
7. Besier, T. F., D. G. Lloyd, J. L. Cochrane, and T. R. Ackland. External loading of the knee joint during running and cutting maneuvers. Med Sci Sports Exerc. 2001;33:1168-1175.
8. Dempsey, A. R., D. G. Lloyd, B. C. Elliott, J. R. Steele, B. J. Munro, and K. A. Russo. The effect of technique change on knee loads during sidestep cutting. Med Sci Sports Exerc. 2007;39:1765-1773.
9. Markolf, K. L., D. M. Burchfield, M. M. Shapiro, M. F. Shepard, G. A. Finerman, and J. L. Slauterbeck. Combined knee loading states that generate high anterior cruciate ligament forces. J Orthop Res. 1995;13:930-935.
10. Piziali, R. L., D. A. Nagel, T. Koogle, and R. Whalen. Knee and tibia strength in snow skiing. In: Ski Trauma and Skiing Safety R. J. Johnson, W. Hauser, and M. Magi (Eds.) Munich: TUV Publication Series, 1982:24-31.
11. Besier, T. F., D. G. Lloyd, and T. R. Ackland. Muscle activation strategies at the knee during running and cutting maneuvers. Med Sci Sports Exerc. 2003;35:119-127.
12. Lloyd, D. G., T. S. Buchanan, and T. F. Besier. Neuromuscular biomechanical modeling to understand knee ligament loading. Med Sci Sports Exerc. 2005;37:1939-1947.
13. Lloyd, D. G. Rationale for training programs to reduce anterior cruciate ligament injuries in Australian football. J Orthop Sports Phys Ther. 2001;31:645-654; discussion 661.
14. Hewett, T. E., T. N. Lindenfeld, J. V. Riccobene, and F. R. Noyes. The effect of neuromuscular training on the incidence of knee injury in female athletes. A prospective study. American Journal of Sports Medicine. 1999;27:699-706.
15. Mandelbaum, B. R., H. J. Silvers, D. S. Watanabe, J. F. Knarr, S. D. Thomas, L. Y. Griffin, et al. Effectiveness of a neuromuscular and proprioceptive training program in preventing anterior cruciate ligament injuries in female athletes: 2-year follow-up. Am J Sports Med. 2005;33:1003-1010.
16. Lloyd, D. G., J. Alderson, and B. C. Elliott. An upper limb kinematic model for the examination of cricket bowling: a case study of Mutiah Muralitharan. J Sports Sci. 2000;18:975-982.
17. Elliott, B. C., J. Alderson, S. Reid, and D. G. Lloyd. Technology and the Law in Cricket: The Muralitharan “Doosra”. . Sports Health. 2005 23:13-15, .
18. Besier, T. F., D. L. Sturnieks, J. A. Alderson, and D. G. Lloyd. Repeatability of gait data using a functional hip joint centre and a mean helical knee axis. J Biomech. 2003;36:1159-1168.