The effect of acute simulated moderate altitude on power, performance and pacing strategies in well-trained cyclists

Athletes regularly compete at 2,000-3,000 m altitude where peak oxygen consumption (VO2peak) declines approximately 10-20%. Factors other than VO2peak including gross efficiency (GE), power output, and pacing are all important for cycling performance. It is therefore imperative to understand how all these factors and not just VO2peak are affected by acute hypobaric hypoxia to select athletes who can compete successfully at these altitudes. Ten well-trained, non-altitude-acclimatised male cyclists and triathletes completed cycling tests at four simulated altitudes (200, 1,200, 2,200, 3,200 m) in a randomised, counter-balanced order. The exercise protocol comprised 5 x 5-min submaximal efforts (50, 100, 150, 200 and 250 W) to determine submaximal VO2 and GE and, after 10-min rest, a 5-min maximal time-trial (5-minTT) to determine VO2peak and mean power output (5-minTT(power)). VO2peak declined 8.2 +/- 2.0, 13.9 +/- 2.9 and 22.5 +/- 3.8% at 1,200, 2,200 and 3,200 m compared with 200 m, respectively, P < 0.05. The corresponding decreases in 5-minTT(power) were 5.8 +/- 2.9, 10.3 +/- 4.3 and 19.8 +/- 3.5% (P < 0.05). GE during the 5-minTT was not different across the four altitudes. There was no change in submaximal VO2 at any of the simulated altitudes, however, submaximal efficiency decreased at 3,200 m compared with both 200 and 1,200 m. Despite substantially reduced power at simulated altitude, there was no difference in pacing at the four altitudes for athletes whose first trial was at 200 or 1,200 m; whereas athletes whose first trial was at 2,200 or 3,200 m tended to mis-pace that effort. In conclusion, during the 5-minTT there was a dose-response effect of hypoxia on both VO2peak and 5-minTT(power) but no effect on GE.

Effect of measuring blood lactate concentrations using different automated lactate analysers on blood lactate transition thresholds

This study investigated the effect of using three automated blood lactate analysers (Accusport, Lactate Pro, YSI 1500 Sport) on blood lactate transition thresholds (BLTT). Blood lactate concentrations were measured using the three analysers in rowers (n = 17) and kayakers (n = 6) during incremental exercise. The BLTT determined were: 1) ADAPT lactate threshold (data point preceding lactate increase of > or = 0.4 mmol x l(-1)), 2) log-log lactate threshold (point of lactate increase when log lactate plotted against log of relevant exercise parameter), 3) DMAX anaerobic threshold, 4) ADAPT anaerobic threshold (modified DMAX method), 5) Onset of blood lactate accumulation (OBLA, fixed blood lactate concentration of 4 mmol x l(-1)). Measurements of blood lactate concentration differed between analysers (p < 0.0001), resulting in BLTT differing between analysers when expressed as a blood lactate concentration (p < 0.0001), or when the BLTT was defined as a fixed blood lactate concentration (e.g. OBLA) (p < 0.0001). When expressed as a power output or heart rate using BLTT based on relative changes in lactate concentration (log-log, ADAPT and DMAX thresholds) the values were similar between analysers (p > 0.05), except the Accusport provided higher values for the log-log lactate threshold (p < 0.0001). We concluded that, despite providing significantly different lactate concentrations, unless the Accusport was used to determine the log-log lactate threshold, or values were expressed as a blood lactate concentration, the use of different analysers had little effect on the BLTT.

Skinfold thickness varies directly with spring coefficient and inversely with jaw pressure

PURPOSE

The main aims of this study were to: 1) determine whether heavy use of Harpenden calipers caused deterioration of the spring coefficient (force per unit length), 2) to quantify the change in skinfold thickness per unit change in jaw closing (downscale) pressure, and 3) to develop a calibration range for these calipers.

METHODS

Part a) The change in spring force per unit length after at least 100,000 cycles of opening and closing five different springs was measured on a load cell. Part b) The dynamic downscale jaw pressure exerted by six pairs of Harpenden springs was measured on one caliper. Two were new pairs of springs (N1 and N2), two were 25-yr-old springs (O1 and O2), and two pairs (S1 and S2) had been used for less 1 yr. The six spring pairs were used to measure skinfold thicknesses at nine sites, in triplicate, on 20 subjects with the order of springs randomized and counterbalanced. Part c) The downscale jaw pressure of 78 Harpenden calipers was measured at eight jaw gaps.

RESULTS

Part a) The springs did not change their characteristics after >100,000 cycles. Part b) At each skinfold site, the lowest thickness was recorded for S2 which exerted the highest jaw pressure (9.04 g x mm(-2)) and conversely the highest thickness was for N1 which exerted the lowest jaw pressure (8.02 g x mm(-2)). Increasing the downscale jaw closing pressure from 8.0 to 9.0 g x mm(-2) reduced a skinfold thickness by approximately 10%. Part c) The mean downscale jaw pressure was 7.82 +/- 0.25 g x mm(-2).

CONCLUSIONS

In summary, it is suggested that if accurate skinfold measures between different Harpenden calipers are required, the downscale jaw pressure should be in the range of 7.40-7.82 and 7.85-8.21 g x mm(-2), at jaw gaps of 5 and 40 mm, respectively. These jaw pressures can be achieved by servicing the caliper pivot and indicator gauge to minimize frictional losses, adjusting the caliper jaw alignment, and by selecting springs that have a spring coefficient in the range 1.10-1.15 N x mm(-1).

Effect of pedal cadence on the accumulated oxygen deficit, maximal aerobic power and blood lactate transition thresholds of high-performance junior endurance cyclists

In this study we investigated the effect of pedal cadence on the cycling economy, accumulated oxygen deficit (AOD), maximal oxygen consumption (VO2max) and blood lactate transition thresholds of ten high-performance junior endurance cyclists [mean (SD): 17.4 (0.4) years; 183.8 (3.5) cm, 71.56 (3.75) kg]. Cycling economy was measured on three ergometers with the specific cadence requirements of: 90-100 rpm for the road dual chain ring (RDCR90-100 rpm) ergometer, 120-130 rpm for the track dual chain ring (TDCR120-130 rpm) ergometer, and 90-130 rpm for the track single chain ring (TSCR90-130 rpm) ergometer. AODs were then estimated using the regression of oxygen consumption (VO2) on power output for each of these ergometers, in conjunction with the data from a 2-min supramaximal paced effort on the TSCR90-130 rpm ergometer. A regression of VO2 on power output for each ergometer resulted in significant differences (P<0.001) between the slopes and intercepts that produced a lower AOD for the RDCR90-100 rpm [2.79 (0.43) l] compared with those for the TDCR120-130 rpm [4.11 (0.78) l] and TSCR90-130 rpm [4.06 (0.84) l]. While there were no statistically significant VO2max differences (P = 0.153) between the three treatments [RDCR90-100 rpm: 5.31 (0.24) l x min(-1); TDCR120-130 rpm; 5.33 (0.25) 1 x min(-1); TSCR90-130 rpm: 5.44 (0.27) l x min(-1)], all pairwise comparisons of the power output at which VO2max occurred were significantly different (P<0.001). Statistically significant differences were identified between the RDCR90-100 rpm and TDCR120-130 rpm tests for power output (P = 0.003) and blood lactate (P = 0.003) at the lactate threshold (Thla-), and for power output (P = 0.005) at the individual anaerobic threshold (Thiat). Our findings emphasise that pedal cadence specificity is essential when assessing the cycling economy, AOD and blood lactate transition thresholds of high-performance junior endurance cyclists.

Reduced performance of male and female athletes at 580 m altitude

This study examined the effect of mild hypobaria (MH) on the peak oxygen consumption (VO2peak) and performance of ten trained male athletes [x (SEM); VO2peak = 72.4 (2.2) ml x kg(-1) x min(-1)] and ten trained female athletes [VO2peak = 60.8 (2.1) ml x kg(-1) x min(-1)]. Subjects performed 5-min maximal work tests on a cycle ergometer within a hypobaric chamber at both normobaria (N, 99.33 kPa) and at MH (92.66 kPa), using a counter-balanced design. MH was equivalent to 580 m altitude. VO2peak at MH decreased significantly compared with N in both men [-5.9 (0.9)%] and women [-3.7 (1.0)%]. Performance (total kJ) at MH was also reduced significantly in men [-3.6 (0.8)%] and women [-3.8 (1.2)%]. Arterial oxyhaemoglobin saturation (SaO2) at VO2peak was significantly lower at MH compared with N in both men [90.1 (0.6)% versus 92.0 (0.6)%] and women [89.7 (3.1)% versus 92.1 (3.0)%]. While SaO2 at VO2peak was not different between men and women, it was concluded that relative, rather than absolute. VO2peak may be a more appropriate predictor of exercise-induced hypoxaemia. For men and women, it was calculated that 67-76% of the decrease in VO2peak could be accounted for by a decrease in O2 delivery, which indicates that reduced O2 tension at mild altitude (580 m) leads to impairment of exercise performance in a maximal work bout lasting approximately 5 min.

Influence of test duration and event specificity on maximal accumulated oxygen deficit of high performance track cyclists

This study examined the relationship between the time required to fully utilise the maximal accumulated oxygen deficit (MAOD) and event specificity of track cyclists. Twelve track endurance and 6 sprint high performance track cyclists performed four treatments of 70 s, 120 s, 300 s and 115% VO2max of maximal cycling on an air-braked ergometer. Peak blood lactate was measured immediately after each test with VO2 kinetics being assessed during the 115% VO2max time to exhaustion test. When the two cycling groups were combined there was no significant difference in the MAOD when assessed under the four different exercise durations. However, when the groups were analysed separately the following results were apparent: (1) the sprint cyclists achieved a significantly greater MAOD (66.9 +/- 2.2 ml.kg-1) compared to the track endurance cyclists (57.6 +/- 6.7 ml.kg-1) when a 70 s test duration was employed (2) even though the track endurance cyclists achieved their greatest MAOD during the 300 s test protocol (62.1 +/- 11.0 ml.kg-1), it was not significantly different to the MAOD's measured during the three other test durations and (3) the sprint cyclists recorded their greatest MAOD during the 70 s supramaximal test protocol (66.9 +/- 2.2 ml.kg-1). This was not significantly different to the 120 s test MAOD, but it was significantly higher than the MAOD values recorded during the 115% VO2max and 300 s test durations. There was no significant difference between the two groups in the peak post-exercise blood lactate concentrations for any of the tests and only the 70 s test produced a significant correlation between peak blood lactate and the MAOD. The VO2 kinetics (VO2 t1/2) of the sprinters was significantly slower than that of the track endurance cyclists (26.3 +/- 2.3 vs 23.9 +/- 2.8 s.). The findings of this study demonstrate that sprint cyclists can fully express their anaerobic capacity within an event specific 70 s all-out test and that these cyclists progressively decrease their anaerobic capacity during a 120 s, 115% VO2max (mean time = 210 s) or 300 s test, despite giving all-out efforts. Conversely, track endurance cyclists achieve their highest mean score during an event specific 300 s test and their lowest during a 70 s test. These findings have important implications when testing high performance cyclists for determination of MAOD, with the implication that it is necessary to assess MAOD under exercise conditions (i.e., duration, pacing) specific to the cyclist's chosen event.

Calibrating skinfold calipers

While athletes are routinely assessed for changes in subcutaneous adipose tissue with skinfold calipers, absolute dynamic calibration of caliper jaw compression is currently not possible. The first part of this study describes how dynamic compression of foam rubber blocks can be used to monitor the relative calibration of a single pair of calipers as springs fatigue, or to alert an investigator to variations in measurement values between different calipers. The second part of the study, carried out on 10 female athletes, demonstrated that the significant differences established by the foam block method of calibration also translated into a significant difference for the sum of seven subcutaneous skinfolds. Foam blocks can be used as a simple, inexpensive method to establish a calibration range and can also be used to recheck calipers periodically, depending upon their use.

Involuntary dehydration during cricket

The sweat rate, heart rate and core temperature as well as urinary volume, osmolarity, electrolyte concentration and pH of 20 cricketers were measured under cool, warm and hot conditions with wet bulb globe temperature indices of 22.1, 24.5 and 27.1, respectively. Simulated match conditions were used on the cool and warm days, while 3 bowlers were measured under actual match conditions on the hot day. The tendency for higher heart rate, sweat rate and renal conservation of water and sodium on the warm day compared with the cool day is consistent with increasing thermoregulatory stress under relatively moderate environmental conditions. The average dehydration of the three fast bowlers was -4.3% of initial body mass after only two sessions of play, on the hot day. This level of dehydration is sufficient to impair physical performance. These results suggest that the adverse effects of dehydration could be minimised if the rules of cricket were amended to allow players the opportunity to drink as desired when the environmental conditions are extreme.

Aerobic and anaerobic indices contributing to track endurance cycling performance

A group of 18 male high performance track endurance and sprint cyclists were assessed to provide a descriptive training season specific physiological profile, to examine the relationship between selected physiological and anthropometric variables and cycling performance in a 4000-m individual pursuit (IP4000) and to propose a functional model for predicting success in the IP4000. Anthropometric characteristics, absolute and relative measurements of maximal oxygen uptake (VO2max), blood lactate transition thresholds (Thla- and Th(an),i), VO2 kinetics, cycling economy and maximal accumulated oxygen deficit (MAOD) were assessed, with cyclists also performing a IP4000 under competition conditions. Peak post-competition blood lactate concentrations and acid-base values were measured. Although all corresponding indices of Thla- and Th(an),i occurred at significantly different intensities there were high intercorrelations between them (0.51-0.85). There was no significant difference in MAOD when assessed using a 2 or 5 min protocol (61.4 vs 60.2 ml.kg-1, respectively). The highest significant correlations were found among IP4000 and the following: VO2max (ml.kg-2/3.min-1; r = -0.79), power output at lactate threshold (Wthla) (W; r = -0.86), half time of VO2 response whilst cycling at 115% VO2max (s; r = 0.48) and MAOD when assessed using the 5 min protocol (ml.kg-1; r = -0.50). A stepwise multiple regression yielded the following equation, which had an r of 0.86 and a standard error of estimate of 5.7 s: IP4000 (s) = 462.9 - 0.366 x (Wthla) - 0.306 x (MAOD) - 0.438 x (VO2max) where Wthla is in W, MAOD is in ml.kg-1 and VO2max is in ml.kg-1 x min-1.(ABSTRACT TRUNCATED AT 250 WORDS)