3 key physiological parameters related to elite cycling performance

Maximal oxygen uptake (VO2 max) is characterized by the upper limit of human’s body aerobic functioning and is a parameter that characterizes the effective integration of the central nervous, cardiopulmonary and metabolic system Day et al., 2003, cited by (Lucia et al., 2006).

VO2 max is used by sports scientist routinely for individual endurance physiological capacity assessment and endurance events prediction (Faria et al., 2006).According to Lucia et al., 2006, for the reasons mentioned above obtaining a valid value of VO2 max can be at significant importance. Even though different VO2 max identification methodologies exist, a valid VO2 max value can be defined as a rate near the end point of exercise with no more increase in VO2, which is dependent primarily on the rate of oxygen supply to the muscle (i.e. convective flow of oxygenated blood to muscle microcirculation as determined in turn by lung diffusing capacity, cardiac output, muscle blood flow, and blood oxygen transport capacity) and secondarily on the muscle oxygen extraction (i.e. from diffusive and perfusive conductance of oxygen from muscle micro-vessels into the working fibres). The relationship and effects between VO2 max and cycling is well examined and described in several studies by Chincaro et al., 2000; Day et al., 2003; Amann et al., 2006, however the different methodologies used during these studies raised a question about the reliability of the different testing protocols; due to the lack of consistency in the terminology it should be pointed out that different research papers and different protocols can define and identify VO2 max in a different way leading to confusion and misunderstanding among the scientific community. Taking into consideration the most recent review on VO2 max and cycling performance by Lucia et al., 2006, can be stated that VO2 max can be obtained after maximal exertion testing defined as the achievement of respiratory exchange ratio (RER) > 1.1,heart rate (HR) > 95% of aged predicted maximum, and blood lactate (Bla) > 8 mmol.l-1.

There are research demonstrated evidence that provide valid information that Maximal Power Output (MPO) obtained during maximal cycling testing can be another predictor of cycling performance Hawley and Noakes, cited by (Faria et al., 2006) reported significant correlation (r = – 0.91; p < 0.001) between maximal power output obtained by exercise testing and 20 (klm) cycle time trial. During graded cycling MPO testing a power to weight ratio of > 5.5 (w/Kg) can be essential requirement for top level performance, however careful examination of the testing protocol that is used need to be considered in order to avoid potential miscalculation which will provide invalid results and false performance evaluation (Faria et al.,2006).

Blood lactate profiling and gas exchange parameters are widely used for monitoring changes in the fitness profile of endurance athletes. Much of this work was directed at determining the lactate (LT) and ventilatory (VT) thresholds. Even though that much research has been done before LT and VT are defined, it should be pointed out that there is no clear agreement on what these terms means. This was and still is a controversial area; however, LT and VT are still commonly used term by coaches, training books, and many sports scientists to separate the physiological stages during exercise. Although the physiological basis for the LT and VT have been controversial Brooks, 1995, reviewers have generally concluded that blood lactate profiling and gas exchange parameters used for the determination of the LT and VT is a rightful mean of monitoring improvements in fitness, prescribing training velocities and predicting exercise performance (Billat, 1996; Jacobs, 1986; Walsh & Bannister ,1998). On the other hand according to Bishop et al., 1998, for facilitation of a more objective approach, investigators have proposed a number of different quantitative procedures to calculate the velocity or power output at the LT and VT, and use them as performance assessment tools.There are different definitions of LT and VT and by reviewing the facts presented by the existing research can be stated that lactate and ventilatory thresholds can be defined as LT1 and LT2, VT1 and VT2. Lactate threshold one is defined as the exercise intensity that elicits 1 mmol.l-1 increase in blood lactate concentration above average rest values, and represents the first break point on the lactate intensity curve. On the other hand LT2 can be defined as the highest exercise intensity at which blood lactate concentration remains stable and is often referred as the maximum lactate steady state (MLSS) furthermore reflects a balance point between lactate production and removal and occurs around 85-90 % of the athletes maximal oxygen consumption (Faria et al.,2006). According to Faria et al., 2006, ventilatory threshold one is the point of non linear increase in ventilation (VE) and carbon dioxide production (VCO2) in combination with a decline in expired CO2 fraction (FECO2) and elevation of expired O2 fraction (FECO2). The second ventilatory threshold is the respiratory compensation point identified as an increase in both VE / VO2 and VE / VCO2 and in decrease in endtidal CO2 tension (PETCO2) in addition can be stated that VT2 and LT2 correspond very closely to each other during exercise.The utility of blood lactate profiling to monitor training induced changes in the LT and its relationship to VT is well described in cycling by (Chincharo et.al., 1999, Bishop et. al., 1998a,199ab)with high correlation coefficient values of (r = 0.81, r = 0.84, r = 0.82) consecutively .

Reviewed by Alexander Marinof Msc.

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