Physiological assesmennt of olympic class sailors

The physiological demands of Olympic Class Sailing are highly specific and vary considerably with the type of boat and wind conditions. The major physical challenge of Olympic Class dinghy sailing is the effort to keep the boat upright in strong winds. This is mainly achieved by hooking the feet under straps, supporting the back of the legs on the deck and suspending the rest of the body over the water. This maneuver, known as ‘hiking’, imposes essentially isometric stress on quadriceps and abdominal muscle groups for periods of many minutes with only a few short intervals of relief. In contrast, in Olympic Class Windsurfing ‘sail pumping’ (a maneuver in which the windsurfer pulls and pushes the sail rhythmically so that it acts as a wing, thus providing the board with additional propulsion) presents the major physical challenge in light to moderate winds.
With the development of portable telemetric technology, measurements of cardiorespiratory requirement under actual sailing conditions have been feasible in recent years (Vogiatzis et al., 1995). Accordingly, in windy conditions dinghy sailing elevates VO2 to an average value of 255 ml/kg/min (50 % VO2max), whereas cardiac function (HR ~ 160 beats/min: ~ 80 % HR max) and ventilation (50 l/min) are challenged proportionally more. This relative tachycardia and hyperventilation have been confirmed and supplemented by electromyographic recordings (EMG), during laboratory boat-specific simulation tests on the same cohort of sailors (Vogiatzis et al., 1996). While VO2 increased moderately (18 ml/kg/min), the development of fatigue in quadriceps was mirrored in the progressive increase in EMG activity (~ 40 % EMG max) and was accounted for the progressive hyperventilation (VE/VO2: 30), tachycardia (130 beats/min) and high blood pressure (mean arterial pressure: 120 mmHg). These responses are in agreement with those reported using other static forms of exercise where blood flow through the muscles is impaired. The average absolute VO2 values measured on- and -off water, in combination with the modest VO2 max values recorded on those sailors (526 ml/kg/min) suggest that aerobic capacity is not particularly taxed in dinghy sailing.
Near-infrared spectroscopy (NIRS) has allowed insights into unresolved issues related to changes in quadriceps oxygenation and blood lactate concentration ([La]b) during hiking. We recently combined, on eight sailors performing five 3-min successive hiking bouts separated by 5-s rest intervals on a simulator, measurements of oxygen uptake (VO2) and earlobe [La]b with determinations of tissue oxygen saturation (StO2) in the vastus lateralis muscle, by continuous-wave NIRS. We additionally assessed the time for 50% resaturation (TR) to the post exercise StO2 peak as a localized indication of the degree of oxygen delivery stress. [La]b was significantly increased throughout hiking maneuvers, though post-exercise values remained low (3.2, s=0.9 mmol l-1). StO2 was significantly reduced compared to baseline (by 35%), indicating an imbalance between muscle oxygen supply and oxygen demand. During the rest intervals StO2 was partially restored. The TR was only 8-s, whereas recovery of StO2 and VO2 were completed within 3-min. We concluded that the observed low [La]b could be attributed to the small oxygen and energy deficits accumulated during hiking as the muscles’ oxygen stores are presumably partially restored during the brief rest intervals.
In contrast to dinghy sailing, a recent study (Vogiatzis et al., 2002) on Olympic-level windsurfers revealed that sail pumping elicits a dramatic increase in cardiorespiratory responses and appears to be as physically demanding as most aerobic sporting activities. During actual windsurfing conditions in light to moderate winds the average values for VO2 and HR were 496 ml/kg/min and 16515 beats/min, respectively. Therefore, sail pumping requires a strenuous aerobic effort as shown by the fractional utilization (75 % VO2max) of VO2max (65 ml/kg/min) that was employed during windsurfing. Interestingly, capillary blood lactate values during sail pumping (typically in the range of 3.5 to 4.5 mM) were very similar to those measured following actual racing conditions (~ 4.0 mM). Based on this observation it is likely that during a typical race lactic acidosis might present a limiting factor to muscular performance, especially in the relatively small but hard working muscles of the upper body.

References

Vogiatzis et al (1995). J Sports Med Phys Fitness 35: 103-107
Vogiatzis et al (1996). Eur J Appl Physiol 72: 195-203
Vogiatzis et al (2002). Eur J Appl Physiol 86: 450-454