Jos J. de Koning

Regulation of pacing strategy during athletic competition.

Background Athletic competition has been a source of interest to the scientific community for many years, as a surrogate of the limits of human ambulatory ability. One of the remarkable things about athletic competition is the observation that some athletes suddenly reduce their pace in the mid-portion of the race and drop back from their competitors. Alternatively, other athletes will perform great accelerations in mid-race (surges) or during the closing stages of the race (the endspurt). This observation fits well with recent evidence that muscular power output is regulated in an anticipatory way, designed to prevent unreasonably large homeostatic disturbances. Principal Findings Here we demonstrate that a simple index, the product of the momentary Rating of Perceived Exertion (RPE) and the fraction of race distance remaining, the Hazard Score, defines the likelihood that athletes will change their velocity during simulated competitions; and may effectively represent the language used to allow anticipatory regulation of muscle power output. Conclusions These data support the concept that the muscular power output during high intensity exercise performance is actively regulated in an anticipatory manner that accounts for both the momentary sensations the athlete is experiencing as well as the relative amount of a competition to be completed.

Optimisation of Sprinting Performance in Running, Cycling and Speed Skating

SummarySprinting performances rely strongly on a fast acceleration at the start of a sprint and on the capacity to maintain a high velocity in the phase following the start. Simulations based on a model developed in which the generation of metabolic power is related to the mechanical destinations of power showed that for short-lasting sprinting events, the best pacing strategy is an all out effort, even if this strategy causes a strong reduction of the velocity at the end of the race. Even pacing strategies should only be used in exercises lasting longer than 80 to 100 seconds.Sprint runners, speed skaters and cyclists need a large rate of breakdown of energy rich phosphates in the first 4 to 5 seconds of the race (mechanical equivalent > 20 W/kg) in order to accelerate their body, and a power output of more than 10 W/kg in the phase following the start to maintain a high velocity. Maximal speed in running is mainly limited by the necessity to rotate the legs forwards and backwards relative to the hip joint. The acceleration phase, however, relies on powerful extensions of all leg joints. Through a comparison of the hindlimb design of highly specialised animal sprinters (as can be found among predators) and of long distance animal runners (as found among hoofed animals), it is illustrated that these 2 phases of a sprint rely on conflicting requirements: improvement of maximal speed would require lower moments of inertia of the legs whereas a faster acceleration would require the involvement of more muscle mass (not only of the hip and knee extensors but also of the plantar flexors).Maximal speed in cycling and speed skating is not limited by the necessity to move leg segments but rather on air friction and rolling or ice friction. Since the drag coefficients found for speed skaters and cyclists (about 0.8) are considerably higher than those of more streamlined bodies, much progress can still be expected from the reduction of air friction. Speed skaters and especially cyclists show much smaller accelerations during the start than do sprint runners. Skaters might try to improve their very first push off by developing a start technique that allows a much more horizontally directed propulsive force. The small propulsive force at the onset of a cycling sprint is due to the gearing system. For sprint cycling (the 1000m time trail and the 4000m pursuit) much progress could be expected from the development of a gearing system that allows a considerably higher propulsive force at the onset of the race and that adapts itself automatically to the velocity.

Ice friction during speed skating

Abstract During speed skating, the external power output delivered by the athlete is predominantly used to overcome the air and ice frictional forces. Special skates were developed and used to measure the ice frictional forces during actual speed skating. The mean coefficients of friction for the straights and curves were, respectively, 0.0046 and 0.0059. The minimum value of the coefficient of ice friction was measured at an ice surface temperature of about −7°C. It was found that the coefficient of friction increases with increasing speed. In the literature, it is suggested that the relatively low friction in skating results from a thin film of liquid water on the ice surface. Theories about the presence of water between the rubbing surfaces are focused on the formation of water by pressure-melting, melting due to frictional heating and on the ‘liquid-like’ properties of the ice surface. From our measurements and calculations, it is concluded that the liquid-like surface properties of ice seem to be a reasonable explanation for the low friction during speed skating.

Neurophysiological Determinants of Theoretical Concepts and Mechanisms Involved in Pacing

Fatigue during prolonged exercise is often described as an acute impairment of exercise performance that leads to an inability to produce or maintain a desired power output. In the past few decades, interest in how athletes experience fatigue during competition has grown enormously. Research has evolved from a dominant focus on peripheral causes of fatigue towards a complex interplay between peripheral and central limitations of performance. Apparently, both feedforward and feedback mechanisms, based on the principle of teleoanticipation, regulate power output (e.g. speed) during a performance. This concept is called ‘pacing’ and represents the use of energetic resources during exercise, in a way such that all energy stores are used before finishing a race, but not so far from the end of a race that a meaningful slowdown can occur.It is believed that the pacing selected by athletes is largely dependent on the anticipated exercise duration and on the presence of an experientially developed performance template. Most studies investigating pacing during prolonged exercise in ambient temperatures, have observed a fast start, followed by an even pace strategy in the middle of the event with an end sprint in the final minutes of the race. A reduction in pace observed at commencement of the event is often more evident during exercise in hot environmental conditions. Further, reductions in power output and muscle activation occur before critical core temperatures are reached, indicating that subjects can anticipate the exercise intensity and heat stress they will be exposed to, resulting in a tactical adjustment of the power output. Recent research has shown that not only climatic stress but also pharmacological manipulation of the central nervous system has the ability to cause changes in endurance performance. Subjects seem to adapt their strategy specifically in the early phases of an exercise task. In high-ambient temperatures, dopaminergic manipulations clearly improve performance. The distribution of the power output reveals that after dopamine reuptake inhibition, subjects are able to maintain a higher power output compared with placebo. Manipulations of serotonin and, especially, noradrenaline, have the opposite effect and force subjects to decrease power output early in the time trial. Interestingly, after manipulation of brain serotonin, subjects are often unable to perform an end sprint, indicating an absence of a reserve capacity or motivation to increase power output. Taken together, it appears that many factors, such as ambient conditions and manipulation of brain neurotransmitters, have the potential to influence power output during exercise, and might thus be involved as regulatory mechanisms in the complex skill of pacing.

The maximal accumulated oxygen deficit method: a valid and reliable measure of anaerobic capacity?

The maximal accumulated oxygen deficit (MAOD) method has been extensively, but unfortunately not very methodically, used; the procedure used to determine the MAOD varies considerably. Therefore, this review evaluates the effect of different numbers and durations of submaximal exercise bouts on the linear power output (PO)-oxygen uptake (V̇O2) relationship and thus the MAOD. Changing the number and duration of the submaximal exercise bouts substantially influences the calculated MAOD when relatively long submaximal exercise bouts are used and no fixed value of the y-intercept is forced into the linear regression line. This is most likely due to non-linearity of the PO-V̇O2 relationship for exercise intensities above the lactate threshold (LT). Non-linearity of the PO-V̇O2 relationship is probably caused by the development of a slow component in V̇O2 during submaximal exercise at intensities above the LT. Thus, it is important to standardize the number, duration and intensity of submaximal exercise bouts necessary to establish the PO-V̇O2 relationship. Beyond changing the number and duration of the submaximal exercise bouts, the effect of different supramaximal exercise bouts on the calculated MAOD has been investigated. While it has become clear that different exercise protocols result in relatively similar values of the MAOD, a closer look at individual data suggests that it may be important to choose an exercise protocol that is representative of the athlete’s event. The validity of the MAOD method was studied by different authors comparing the MAOD with metabolic measurements of anaerobic adenosine triphosphate (ATP) production. The main limitation with the metabolic measurements of anaerobic ATP production from muscle biopsy data is that the active muscle mass is unknown, which makes it hard to accurately study the validity of the MAOD method. From the studies that evaluated the reliability of the MAOD method it is clear that the MAOD method may not be a reliable measure of anaerobic capacity. From these findings it can be concluded that the MAOD method may have limitations as a valid and reliable measure of anaerobic capacity and needs to be further improved. We suggest the use of 10 x 4 minute submaximal exercise bouts and a fixed value of the y-intercept for the construction of the linear PO-V̇O2 relationship, after which the MAOD can be determined during a supramaximal exercise protocol specific for the athlete’s event. This method will lead to a more robust PO-V̇O2 relationship and will therefore result in more valid and reliable results.

Coordination of leg muscles during speed skating

Abstract Five speed skaters of elite performance level and six speed skaters of trained level were subjected to an inverse dynamical analysis during speed skating. Push-off forces were registered by means of special skates. Myoelectric activity (EMG) of ten leg muscles and cinematographic data were recorded. Linked segment modelling yielded net joint moments and joint powers. The speed skating technique is characterized by a typical horizontal position of the trunk and a suppression of a plantar flexion during the push-off. This technique, necessary to reduce external friction, constrains the transfer of rotation in joints to translation of the mass center of the body. In spite of constrained push-off, the EMG levels of the leg muscles show a proximo-distal temporal order which to a certain extent is comparable to that previously found in an unconstrained vertical jump. This proximo-distal sequence is also reflected by the time courses of the net moment and net power output in hip, knee and ankle joints. The temporal sequence in activation levels of activated muscles is not different between elite and trained speed skaters. The difference in performance level between these groups obviously has an origin in the ability of the elite speed skaters to realise larger net joint moments. Differences in net joint moments and in kinematics result in a higher power output and a lower air frictional force for the elite than for the trained speed skaters.

Pacing in Olympic track races: Competitive tactics versus best performance strategy

Abstract The purpose of this study was to describe pacing strategies in the 800 to 10,000-m Olympic finals. We asked 1) if Olympic finals differed from World Records, 2) how variable the pace was, 3) whether runners faced catastrophic events, and 4) for the winning strategy. Publically available data from the Beijing 2008 Olympic Games gathered by four transponder antennae under the 400-m track were analysed to extract descriptors of pacing strategies. Individual pacing patterns of 133 finalists were visualised using speed by distance plots. Six of eight plots differed from the patterns reported for World Records. The coefficient of running speed variation was 3.6–11.4%. In the long distance finals, runners varied their pace every 100 m by a mean 1.6–2.7%. Runners who were ‘dropped’ from the field achieved a stable running speed and displayed an endspurt. Top contenders used variable pacing strategies to separate themselves from the field. All races were decided during the final lap. Olympic track finalists employ pacing strategies which are different from World Record patterns. The observed micro- and macro-variations of pace may have implications for training programmes. Dropping off the pace of the leading group is an active step, and the result of interactive psychophysiological decision making.

From biomechanical theory to application in top sports: the Klapskate story

The development of the new skate design specifically the klapskate in a historical and scientific perspective is described. Reasons why it took so long for top athletes to use the new skate design is explained. The klapskate demonstrated its advantage over conventional skates and proved its benefits.

A power equation for the sprint in speed skating

An analysis of the start of the 500 m speed skating races during the 1988 Olympic Winter Games showed a remarkably high correlation between the acceleration of the skater in the first second of the sprint and the final time (r = -0.75). In this study a power equation is used to explain this high coefficient of correlation. The performance in speed skating is determined by the capability of external power production by the speed skater. This power is necessary to overcome the air and ice friction and to increase the kinetic energy of the skater. Numerical values of the power dissipated to air and ice friction, both dependent on speed, are obtained from ice friction and wind tunnel experiments. Using aerobic and anaerobic power production as measured during supra maximal bicycle tests of international-level speed skaters, a model of the kinetics of power production is obtained. Simulation of power production and power dissipation yields values of speed and acceleration and, finally, the performance time of the sprint during speed skating. The mean split time at 100 m and the final time at 500 m in these races, derived from simulation, were 10.57 s (+/- 0.31) and 37.82 s (+/- 0.96), respectively. The coefficient of correlation between the simulated 500 m times and the actual 500 m times was 0.90. From the results of this study it can be concluded that the distribution of the available anaerobic energy is an important factor in the short lasting events. For the same amount of anaerobic energy the better sprinters appear to be able to liberate considerably more energy at the onset of the race than skaters of lower performance level.

A new skate allowing powerful plantar flexions improves performance

To prevent the tip of the blade from scratching through the ice, the technique in speed skating requires that plantar flexion is largely suppressed during the gliding push off. This not only prevents the plantar flexors from contributing to external work but also causes the skater to lose contact with the ice long before the knee is fully extended. To prevent these disadvantages of the gliding technique, a new skate was developed that permits the shoe to rotate relative to the blade in a hinge between shoe and blade. In a case control study the progression between the 1993/1994 and 1994/1995 skating seasons of 11 male skaters from a regional junior selection who consented to switch to this new skate was compared with the progression of 72 skaters of this and all other regional and national male junior selections of The Netherlands. The experimental group appeared to improve their personal best times by 6.2 +/- 2.3%, which is a significantly (P < 0.001) larger progress than the 2.5 +/- 1.6% improvement of the control group. The new skate will therefore most likely add a new dimension to the art of speed skating.