Dr Graham Askew
Associate Professor in Biomechanics (Leeds, 2011-)
Lecturer (Leeds 2001-2011)
I studied Biology at the University of Leeds and remained there to carry out a PhD on the effects of training and fatigue on the mechanical properties of skeletal muscle. I carried out postdoctoral research at Northeastern University in Boston and the University of Cambridge. I returned to the University of Leeds as a lecturer in 2001.
- Deputy Director of Postgraduate Research Studies (School of Biomedical Sciences, Admissions)
My research focuses on the physiology and biomechanics of animal movement. The overall goal of the lab is to understand how muscle mechanical function and energetics determine the overall metabolic energy expenditure and physical performance of locomotion. We use an integrative and comparative approach to reveal the underlying cellular, physiological and biomechanical determinants of physical performance in order to understand the evolution of musculoskeletal design.
Mechanical function of muscles during locomotion
A large part of our work has investigated muscle function during flight because during flight the bulk of the active muscles have a simple mechanical function – to generate power. We have studied the explosive take-off flights performed by some birds to investigate the physiological adaptations that allow muscles to generate maximal short-term power output. One of the species that we studied – the blue-breasted quail – develops the highest power of any skeletal muscle yet measured (per gram of muscle; Askew and Marsh, 2001). Bird flight also proved to be a useful system in which to investigate power modulation strategies. The need to modulate power is relevant to many activities including acceleration, incline locomotion, and speed related variation in power requirements. We have been able to determine the importance of power modulation through changes in muscle recruitment and length trajectory as well as at the level of the organism by the use of intermittent flight behaviour (Askew and Ellerby, 2007; Morris and Askew, 2010).
In vivo zebra finch pectoralis fascicle strain and EMG activity at 10 m s-1. Fascicle length was measured by sonomicrometry. Muscle activity was measured using a bipolar EMG electrode.
Energetics of Locomotion
My laboratory also investigates metabolic energy use during locomotion with the primary aim of quantifying energy use of the locomotory muscles in order to gain a better understanding of the determinants of whole organismal energy use. We use whole organism metabolic rate is determined by measuring O2 consumption and CO2 production during locomotion (Fig. 2; Morris and Askew, 2010). In leaf-cutter ants this technique has been used to investigate the behavioural adaptations that occur during the negotiation of hilly terrain (Holt and Askew, 2012). We also investigated the effects that wearing armour would have had on the locomotion of Medieval knights (Askew et al., 2011), finding that when wearing the armour the energy expenditure was doubled when they walked or ran. This is much more than wearing a backpack of equivalent mass due to the increased cost of swinging the loaded limbs and impaired breathing when wearing armour. These findings can help historians interpret the feats of battle. At the level of the muscle, we quantify energy use by measuring the total enthalpy output (the sum of the mechanical work and heat production) and also, indirectly, by measuring regional blood flow. Our research has demonstrated that a muscle doing stretch-shorten work uses no more energy than when force is produced isometrically, challenging the view that elastic tendons reduce locomotor costs by replacing muscle work (Holt et al., 2014). We have also developed approaches that allow energy use can also be quantified at the level of the cross-bridges (Askew et al., 2010).
Using respirometry to measure metabolic energy expenditure during locomotion - while walking in Medieval armour and during flight in a cockatiel
Integrating the Mechanics and Energetics of Locomotion
During all modes of locomotion, muscles convert chemical energy into mechanical work that is ultimately transferred to the environment to produce movement. To achieve a full understanding of the system, we need to be able to trace the transfer of energy between all levels of organisation from the contractile proteins to the momentum transferred to the animal's wake and relate this to the animal's locomotor performance, morphology and ecology.
- An integrated approach towards characterising the functional mechanics and energetics of insect flight muscles. The aim of this project is to use an integrated approach to gain a detailed understanding of the mechanics, energetics and function of the steering and powering flight in insects. This project is in collaboration with Dr Simon Walker and funded by the BBSRC.
- Bird flight energetics – from tissues to free flight. The overall aim of this project is to determine the relationship between the mechanical performance and metabolic energy utilisation of birds during flight, its partitioning at the level of individual muscles, and the functional linkage to the indirect measures of heart rate, wingbeat frequency and dynamic body acceleration. This project is in collaboration with Dr Charles Bishop (Bangor University) and funded by the BBSRC.
- A new framework for computational biomechanical models and 3Rs in musculoskeletal research. The aim of this research is to develop biologically validated biomechanical models of rabbit mastication and to establish a framework for the development, application and acceptance of such computational models of hard and soft tissue biomechanics and physiology with the aim of encouraging their wider use, in particular in 3Rs. This project is in collaboration with Prof. Michael Fagan (University of Hull), Dr Peter Watson (University of Hull) and Dr Karl Bates (University of Liverpool) and funded by the BBSRC.
Research in my laboratory is funded by the BBSRC.
Swimming efficiency in a “living fossil” – chambered nautilus encounter oxygen deficient waters when they dive to forage. To conserve their limited on-board oxygen supplies, their metabolic cost of locomotion needs to be low. By measuring the wake structure in Nautilus, we were able to show that they have a higher propulsive efficiency than has been measured in other animals that swim using jet propulsion. The high propulsive efficiency in Nautilus contributes to the low metabolic cost of swimming and is a strategy to reduce the metabolic demands in an animal that spends a significant part of its daily life in a low-oxygen environment.
Neil T.R., Askew, G.N. Swimming mechanics and propulsive efficiency in the chambered nautilus. Royal Society Open Science 5, 2018. DOI:10.1098/rsos.170467
Paper highlighted in New York Times - https://www.nytimes.com/2018/02/23/science/chambered-nautilus-jet-propulsion.html
Running energetics – in this paper we tested the idea that tendons save energy by reducing cyclic muscle work by comparing the cost of force generation during constant length muscle actions with active stretch-shorten cycles.
Holt, N.C, Roberts, T.J. and Askew, G.N. The energetic benefits of tendon springs in running: is the reduction of muscle work important? J. Exp. Biol. 217, 4365-4371. 2014. doi: 10.1242/ jeb.112813
Peacock’s train is not such a drag – here I measured the effect that the elaborate plumage of male peafowl has on their take-off performance.
Askew, G.N. The elaborate plumage in peacocks is not such a drag. J. Exp. Biol. 217, 3237-3241. 2014.
Paper highlighted in Inside JEB. J. Exp. Biol. 217, 3189; doi: 10.1242/ jeb.112342 and online (ScienceNow, Huffington Post, Times of India, Nature World News)
Photo by G.Askew
Energetics of locomotion in Medieval armour – here we measured how much effort is required to walk and run while wearing armour.
Askew, G.N., Formenti, F., Minetti, A.E. Limitations imposed by wearing armour on Medieval soldiers’ locomotor performance. Proc. R. Soc. Lond. B 279, 640-644. 2012.
Ant energetics – in this paper we measured the energetic cost of walking uphill and downhill in leaf cutter ants in order to understand the behaviour of route selection.
Holt, N. and Askew, G.N. Locomotion on a slope: metabolic energy use, behavioural adaptations and the implications for route selection. J. Exp. Biol. 215, 2545-2550. 2012.
Photo by G. Askew
Power modulation in bird flight –this is a series of three papers on cockatiel flight in which we quantify muscle mechanical performance during flight using two methods and compared this to the metabolic cost of flight.
Morris, C.R. and Askew, G.N. Power modulation strategies and the mechanical power requirements of flight in the cockatiel (Nymphicus hollandicus). J. Exp. Biol., 213, 2770-2780. 2010.
Morris, C.R., Nelson, F.E. and Askew, G.N. The metabolic power requirements of flight and estimations of flight muscle efficiency in the cockatiel (Nymphicus hollandicus). J. Exp. Biol., 213, 2788-2796. 2010.
Morris, C.R. and Askew, G.N. Comparison between mechanical power requirements of flight estimated using an aerodynamic model and in vitro muscle performance in the cockatiel (Nymphicus hollandicus). J. Exp. Biol. 213, 2781-2787. 2010.
Papers highlighted in Inside JEB. Journal of Experimental Biology 213, I (2010). doi:10.1242/jeb.04911114
- BSc 1992, Leeds
- PhD 1995, Leeds
- Society for Experimental Biology
Undergraduate project topics:
- Mechanics and energetics of locomotion
- Thermal physiology
- Proxies of metabolic energy expenditure
Postgraduate studentship areas:
- Muscle performance and energetics during locomotion
- Bird and insect flight
- Scaling of muscle performance
Research groups and institutes
- Sport and Exercise Sciences