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Exp Physiol 95.3 pp 404–410
Experimental Physiology – Themed Issue Review
Limitations to performance during alpine skiing Richard A. Ferguson School of Sport, Exercise and Health Sciences, Loughborough University, Leicestershire LE11 3TU, UK
Alpine skiing is characterized by high-intensity exercise of between 90 and 120 s duration that requires repeated phases of high-force isometric and eccentric contractions. The nature of these contractions, during which all fibre types are active, results in restricted blood flow to the working muscle, thereby reducing oxygen delivery and increasing metabolite accumulation. The consequence of this will be skeletal muscle fatigue, through both central and peripheral mechanisms, and a potential loss of motor control which will ultimately limit skiing performance. (Received 2 August 2009; accepted after revision 3 November 2009; first published online 6 November 2009) Corresponding author R. A. Ferguson: School of Sport, Exercise and Health Sciences, Loughborough University, Leicestershire LE11 3TU, UK. Email:
[email protected]
Alpine skiing has been contested at every Winter Olympics since 1936 and consists of the four traditional events of downhill (DH), super giant slalom (SG), giant slalom (GS) and slalom (SL), as well as events such as moguls and snowboarding. The events are approximately 90 s in duration for the GS and SL and up to 2 min for the DH and SG. All events require the skier to accelerate as quickly as possible from the starting gate to full speed before maintaining proper form and technique for the remainder of the race. Elite ski racing is performed at speeds that can approach 160 Km h−1 (DH), or takes place on extremely steep terrain (SL). Therefore, there are immense physical requirements for elite skiers to anchor the whole body in a streamlined and aerodynamic position (DH and GS) or make tight turns in rapid succession (SG and SL). Given that the margins between gold and silver medals in the Winter Olympic alpine skiing events are measured to the hundredth of a second, understanding any of the factors that limit performance is of importance. The physical characteristics of skiers and requirements for the various events have been previously described (Turnbull et al. 2009). The energy demand of skiing is often measured in terms of maximal oxygen uptake (V˙ O2 max ). Tesch et al. (1978) observed energy demands equivalent to ∼80–90% V˙ O2 max during DH skiing, whereas Saibene et al. (1985) reported energy demands equivalent to 120% V˙ O2 max during GS skiing. Veicsteinas et al. (1984) observed much higher demands equivalent to ∼160–200% V˙ O2 max during SL and GS events, in which the oxygen cost of anaerobic sources was accounted for through measurements of postexercise blood lactate concentration. What have been less well explored, however, are the specific responses that occur within the skeletal muscle during DOI: 10.1113/expphysiol.2009.047563
skiing and how these responses may influence skiing performance. The focus of this brief review, therefore, is to discuss some of the fundamental aspects of skeletal muscle physiology in relation to the available skiingspecific knowledge in order to understand what the main factors might be that limit performance in alpine skiing.
Contractile activity and muscle fibre recruitment during alpine skiing
In order to appreciate the limitations to performance in alpine skiing events, the type of contraction and level of activity of the main muscle groups involved and the subsequent physiological consequences of their involvement must be considered. Berg et al. (1995) and Berg & Eiken (1999) observed high levels of EMG activity and a predominance of high-force, slow-velocity eccentric contractions of the quadriceps muscle group during SG, GS and SL events. This is probably due to the low posture assumed during these events, as well as the downward displacement of the body, especially during turns. Hintermeister et al. (1995) observed high levels of EMG activity in the majority of leg (including quadriceps, hamstrings and calf) and trunk muscles studied during GS and SL events. They also observed evidence of cocontraction and suggested that there is a significant isometric component to skiing. The high level of EMG activity measured during skiing events would suggest that a significant proportion of the muscle is active. The studies by Tesch et al. (1978) and Nygaard et al. (1978) set the benchmark for understanding which fibre types may be active during skiing. Both studies C 2009 The Author. Journal compilation C 2010 The Physiological Society
Exp Physiol 95.3 pp 404–410
Limitations to performance during alpine skiing
used the histochemical measurement of glycogen, using the periodic acid–Schiff (PAS) reaction, where crosssections of frozen muscle biopsies obtained before and after skiing activity were stained according to different levels of glycogen content, providing a semi-quantitative assessment of glycogen utilization. Serial cross-sections were also stained to characterize the fibres as either slowtwitch (ST) or fast-twitch (FT) fibre types. The consensus from these studies was that a greater utilization of glycogen occurred in ST fibres, suggesting a greater use of these fibres during skiing. An important limitation to this technique, however, is that exercise of a relatively long duration (>10 min) is necessary to detect a decline in the PAS staining intensity. Moreover, the glycogen depletion patterns in these studies were monitored during a whole day of skiing and are therefore not representative of a single bout of skiing activity. Given these methodological limitations, together with the short duration of ski races and the high level of EMG activity (Berg et al. 1995; Hintermeister et al. 1995; Berg & Eiken, 1999), it is probable that the pattern of muscle fibre recruitment may not be as described. Physiological experiments conducted over the past 15 years have enhanced our knowledge of muscle fibre recruitment patterns during brief (
