The data collection and analysis of this research study was largely the work of Frans Nollet and Anita Beelen. Other senior authors provided input at various stages of planning and writing. Professor Anthony J Sargeant was the supervisor for the PhD thesis of which this work formed a part.
Frans Nollet, Anita Beelen, Prins MH, Marianne de Visser, Anthony J Sargeant, Lankhorst GJ, de Jong BA
Archives of Physical Medicine and Rehabilitation
This research was part of work completed by the brilliant PhD student, Costis Maganaris (now a full Professor in Liverpool), who was supervised by Professor Vasilios Baltzopoulos and Anthony Sargeant.
Differences in human antagonistic ankle dorsiflexor coactivation between legs; can they explain the moment deficit in the weaker plantarflexor leg
This research published in the Journal of Neurophysiology was carried out in Amsterdam by Jo De Ruiter as part of his doctoral thesis supervised by Professor Anthony J Sargeant and Arnold de Haan. It was part of a series of studies examining the regional differences within a single muscle of physiological properties and hence pattern of recruitment in response to different intensities of exercise.
In this research published in Journal of Physiology Anthony Sargeant and his team describe how the recruitment of different types of muscle fibres with increasing exercise intensity changes the oxygen cost of exercise. Thus the relationship of oxygen uptake and mechanical power output is not constant. This is in contrast to the standard teaching of many physiology textbooks.
Non-linear relationship between O2 uptake and power output at high intensities of exercise in humans
The ability of generating muscle power power is important whether you are an Olympic athlete, a ballet dancer, or an elderly person wanting to climb the stairs to go to bed. In this comprehensive review of his research Anthony Sargeant points out the importance of different types of muscle fibres that make up the human skeletal muscles that produce power in legs and arms. Tony also points out that in research seeking to measure human muscle power it is essential to measure or control the speed at which the power is generated (this is because power is the product of work and velocity).
Structural and functional determinants of human muscle power
by Anthony J Sargeant
Exp Physiol. 2007 Mar;92(2):323-31
Measurements of human power need to be interpreted in relation to the movement frequency, since that will determine the velocity of contraction of the active muscle and hence the power available according to the power-velocity relationship. Techniques are described which enable movement frequency to be kept constant during human exercise under different conditions. Combined with microdissection and analysis of muscle fibre fragments from needle biopsies obtained pre- and postexercise we have been able ‘to take the muscle apart’, having measured the power output, including the effect of fatigue, under conditions of constant movement frequency. We have shown that fatigue may be the consequence of a metabolic challenge to a relatively small population of fast fatigue-sensitive fibres, as indicated by [ATP] depletion to approximately 30% of resting values in those fibres expressing myosin heavy chain isoform IIX after just 10 s of maximal dynamic exercise. Since these same fibres will have a high maximal velocity of contraction, they also make a disproportionate contribution to power output in relation to their number, especially at faster movement rates. The microdissection technique can also be used to measure phosphocreatine concentration ([PCr]), which is an exquisitely sensitive indicator of muscle fibre activity; thus, in just seven brief maximal contractions [PCr] is depleted to levels < 50% of rest in all muscle fibre types. The technique has been applied to study exercise at different intensities, and to compare recruitment in lengthening, shortening and isometric contractions, thus yielding new information on patterns of recruitment, energy turnover and efficiency.