Sprint performance requires the ability to accelerate, achieve a high maximum velocity and be able to sustain maximal velocity under conditions of fatigue (Ross, et al., 2001). Sprint ability is, therefore, characterised: in neuromuscular performance by fast activation and coordination of muscle fibres; in metabolic performance by the ability to withstand fatiguing effects of intensive anaerobic ATP production; and in anthropometry by volume and quality of muscle mass with respect to the size of the rider (Bowman & Brown, 2012; Craig & Norton, 2001).
Power output demands for sprint cyclists are dictated by a number of variables. These include rider size and position, bike design, bike-rider speed, rolling resistance, air resistance and demands of the specific event (Martin et al., 2007). The maximum power a rider can produce will depend on such
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factors as pedalling rate, muscle size and fibre-type distribution, riding position and degree of fatigue (Faria et al., 2005a). It is commonly accepted that power is primarily produced at the crank by contribution of muscles spanning the hip, knee and ankle, whereas McDaniel et al. (2005) suggested that in sprint cycling as much as 9% of the total contribution may be derived from transmission across the hip - in effect the core and upper body musculature. Further, Davidson et al. (2005) have determined that the additional power delivered in a standing start is achieved by increased contribution of upper body, while joint power contribution of the hip, knee and ankle remains unchanged. In such cases, to maximise potentiation of relevant neuromuscular pathways, the CC stimulus will require consideration of upper and lower limb contributions.
Additional constraints on the ability to generate power are imposed by the bike itself. The use of a fixed, single gear requires a trade-off between overcoming inertia in accelerating from standing start or low speed and the maximum leg speed achieved at peak velocity later in the sprint. Bike set-up, including rider position, choice of gear and crank length will, therefore, dictate performance along the force-length-velocity relation of contributing muscles (Martin, et al., 2007; Martin & Spirduso, 2001). In the 200 m event, where world class times are of the order of 10 seconds, riders will generate peak torques of over 300 Nm at the outset, achieving peak velocity of around 65 km/h and cadences of 150 rpm by the finish (Craig & Norton, 2001; Schumacher et al., 2001). With muscle shortening velocity determined by pedal speed, muscle power will increase off the line, peak and then decline as pedal speed reaches maximum (Martin, et al., 2007). Pedal rate, or cadence, will, additionally, influence excitation-relaxation kinetics (Neptune & Kautz, 2001), while pedal technique and the ability to effectively direct force round the pedal stroke will influence the transfer of muscular force to forward motion of the bike-rider system (Abbiss et al., 2009; Hug et al., 2008). The interaction of these two factors will consequently determine whether peak force will be produced in the optimal (80-110°) sector of the crank for generating external power (Gregor, 2000). In fact,
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electromechanical delay (EMD) and pedal stroke variability show increasingly negative effects on power production at higher cadences (Ettema et al., 2009).
Over the course of sprint events, the rider will use both standing and seated riding positions and will be required to achieve maximal performance over an extensive range of the force-velocity-power (FVP) relationship (Craig & Norton, 2001). Optimising conditions for sprint cycling performance, therefore, not only requires the increase of temperature and acidosis levels within appropriate range, but, in addition, should facilitate maximum motor unit recruitment, maximum motor unit discharge rates, fastest nerve conduction and temporal sequencing of muscle activation, maximum rate and efficiency of excitation-contraction coupling and cross-bridge recycling, while positively affecting the hormonal milieu and avoiding any degree of metabolic fatigue (Bishop, 2003b; Cormie, et al., 2011; Madon, 2007; Tomaras & MacIntosh, 2011; Wittekind & Beneke, 2011). In the tightly- constrained bike-rider system the efficacy of potentiation is undoubtedly observed in supporting potential benefits to psychomotor function, as well as both central and peripheral components of the neuromuscular chain of command.
Finally, it is essential to acknowledge that cycling power is generated by predominantly concentric muscle action. Potentiation studies have had some success in cycling outcomes (Jo, et al., 2010; Lawrence, et al., 2010; J. C. Smith, et al., 2001; Thatcher, et al., 2012), and, in such cases, potentiation cannot be a simple augmentation of the stretch reflex or stretch-shortening cycle (SSC) action, as has been suggested (Cabrera, et al., 2009). In fact, prior consideration of PTP studies has revealed the greater potential for response in concentric contractions and cycling presents an ideal movement pattern to validate this finding in whole body performance. Although Bishop (2003b) suggests that temperature related reduction in muscle and joint stiffness would benefit explosive exercise, Watsford et al. (2010) recently showed that an increased musculoarticular (MA) stiffness
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was beneficial to sprint cycling. In support, Ditroilo et al. (2011) have confirmed that a decline in MA stiffness with fatigue significantly impairs performance in a 6-second cycle sprint. The lack of SSC component in the cycling action may impose somewhat different requirements of MTU compliance (Stafilidis & Arampatzis, 2007). In such a case the structural and architectural impacts of preload CC could represent an auxiliary benefit of PAP to sprint cycling performance.
The merit of incorporating a CC protocol into a sprint cycling warm-up is evident and, in fact, could provide a means to surmount the compromises required by existing preparatory strategies. Definition of an appropriate protocol may be made through appraisal of existing performance studies.