Jesús Hoyos

Hormone levels of world class cyclists during the Tour of Spain stage race

Objectives—To evaluate the hormonal response to strenuous endurance exercise performed by elite athletes. Methods—Nine professional cyclists (mean (SD) age 28 (1) years; mean (SD) Vo2max 75.3 (2.3) ml/kg/min) who participated in a three week tour race (Vuelta a España 1999) were selected as subjects. Morning urinary levels of 6-sulphatoxymelatonin (aMT6s) and morning serum levels of testosterone, follicle stimulating (FSH), luteinising hormone (LH), and cortisol were measured in each subject at t0 (before the competition), t1 (end of first week), t2 (end of second week), and t3 (end of third week). Urine samples of aMT6s were also evaluated in the evening at t0, t1, t2, and t3. Results—Mean urinary aMT6s levels had increased significantly (p<0.01) during the day after each stage (1091 (33) v 683 (68) ng/ml at t1; 955 (19) v 473 (53) ng/ml at t2; 647 (61) v 337 (47) ng/ml at t3). Both morning and evening aMT6s levels decreased significantly during the study. A similar pattern was observed for morning serum levels of cortisol and testosterone. Conclusions—The results suggest that the basal activity of the pineal gland, adrenal glands, and testis may be decreased after consecutive days of intense, long term exercise.

The slow component of VO2 in professional cyclists.

Objectives—To analyse the slow component of oxygen uptake (V̇o2) in professional cyclists and to determine whether this phenomenon is due to altered neuromuscular activity, as assessed by surface electromyography (EMG). Methods—The following variables were measured during 20 minute cycle ergometer tests performed at about 80% of V̇o2max in nine professional road cyclists (mean (SD) age 26 (2) years; V̇o2max 72.6 (2.2) ml/kg/min): heart rate (HR), gas exchange variables (V̇o2, ventilation (V̇e), tidal volume (VT), breathing frequency (fb), ventilatory equivalents for oxygen and carbon dioxide (V̇e/V̇o2 and V̇e/V̇co2 respectively), respiratory exchange ratio (RER), and end tidal Po2 and Pco2 (Peto2 and Petco2 respectively)), blood variables (lactate, pH, and [HCO3−]) and EMG data (root mean from square voltage (rms-EMG) and mean power frequency (MPF)) from the vastus lateralis muscle. Results—The mean magnitude of the slow component (from the end of the third minute to the end of exercise) was 130 (0.04) ml in 17 minutes or 7.6 ml/min. Significant increases from three minute to end of exercise values were found for the following variables: V̇o2 (p<0.01), HR (p<0.01), V̇e (p<0.05), fb (p<0.01), V̇e/V̇o2 (p<0.05), V̇e/V̇co2 (p<0.01), Peto2 (p<0.05), and blood lactate (p<0.05). In contrast, rms-EMG and MPF showed no change (p>0.05) throughout the exercise tests. Conclusions—A significant but small V̇o2 slow component was shown in professional cyclists during constant load heavy exercise. The results suggest that the primary origin of the slow component is not neuromuscular factors in these subjects, at least for exercise intensities up to 80% of V̇o2max.

Relation between physical exertion and heart rate variability characteristics in professional cyclists during the Tour of Spain

Background: Continued exposure to prolonged periods of intense exercise may unfavourably alter neuroendocrine, neuromuscular, and cardiovascular function. Objective: To examine the relation between quantifiable levels of exertion (TRIMPS) and resting heart rate (HR) and resting supine heart rate variability (HRV) in professional cyclists during a three week stage race. Method: Eight professional male cyclists (mean (SEM) age 27 (1) years, body mass 65.5 (2.3) kg, and maximum rate of oxygen consumption (V˙o2max) 75.6 (2.2) ml/kg/min) riding in the 2001 Vuelta a España were examined for resting HR and HRV on the mornings of day 0 (baseline), day 10 (first rest day), and day 17 (second rest day). The rest days followed stages 1–9 and 10–15 respectively. HR was recorded during each race stage, and total HR time was categorised into a modified, three phase TRIMPS schema. These phases were based on standardised physiological laboratory values obtained during previous V˙o2max testing, where HR time in each phase (phase I  =  light intensity and less than ventilatory threshold (VT; ∼70% V˙o2max); phase II  =  moderate intensity between VT and respiratory compensation point (RCP; ∼90% V˙o2max); phase III  =  high intensity (>RCP)) was multiplied by exertional factors of 1, 2, and 3 respectively. Results: Multivariate analysis of variance showed that total TRIMPS for race stages 1–9 (2466 (90)) were greater than for stages 10–15 (2055 (65)) (p<0.0002). However, TRIMPS/day were less for stages 1–9 (274 (10)) than for stages 10–15 (343 (11)) (p<0.01). Despite a trend to decline, no difference in supine resting HR was found between day 0 (53.2 (1.8) beats/min), day 10 (49.0 (2.8) beats/min), and day 17 (48.0 (2.6) beats/min) (p  =  0.21). Whereas no significant group mean changes in HR or HRV indices were noted during the course of the race, significant inverse Pearson product-moment correlations were observed between all HRV indices relative to total TRIMPS and TRIMPS/day accumulated in race stages 10–15. Total TRIMPS correlated with square root of mean squared differences of successive RR intervals (r  =  −0.93; p<0.001), standard deviation of the RR intervals (r  =  −0.94; p<0.001), log normalised total power (r  =  −0.97; p<0.001), log normalised low frequency power (r  =  −0.79; p<0.02), and log normalised high frequency power (r  =  −0.94; p<0.001). Conclusion: HRV may be strongly affected by chronic exposure to heavy exertion. Training volume and intensity are necessary to delineate the degree of these alterations.

Kinetics of VO(2) in professional cyclists.

PURPOSE To analyze the kinetics of oxygen uptake (VO(2)) in professional road cyclists during a ramp cycle ergometer test and to compare the results with those derived from well-trained amateur cyclists. METHODS Twelve professional cyclists (P group; 25 +/- 1 yr; maximal power output (W(max)), 508.3 +/- 9.3 watts) and 10 amateur cyclists (A group; 22 +/- 1 y; W(max), 429.9 +/- 8.6 watts) performed a ramp test until exhaustion (power output increases of 25 watts x min(-1)). The regression lines of the VO(2):power output (W) relationship were calculated for the following three phases: phase I (below the lactate threshold (LT)), phase II (between LT and the respiratory compensation point (RCP)), and phase III (above RCP). RESULTS In group P, the mean slope (Delta VO(2):Delta W) of the VO(2):W relationship decreased significantly (P < 0.01) across the three phases (9.9 +/- 0.1, 8.9 +/- 0.2, and 3.8 +/- 0.6 mL O(2) x watts(-1) x min(-1) for phases I, II, and III, respectively). No significant differences (P > 0.05) were found between phases I and II (P > 0.05) in group A, whereas Delta VO(2):Delta W significantly increased in phase III (P < 0.01), compared with phase II (10.2 +/- 0.3, 9.2 +/- 0.4, and 10.1 +/- 1.1 mL O(2) x watts(-1) x min(-1) in phases I, II, and III, respectively). The mean value of Delta VO(2):Delta W for phase III was significantly lower in group P than in group A (P < 0.01). CONCLUSION Contrary to the case in amateur riders, the rise in VO(2) in professional cyclists is attenuated at moderate to high workloads. This is possibly an adaptation to the higher demands of their training/competition schedule.

Effects of endurance training on the isocapnic buffering and hypocapnic hyperventilation phases in professional cyclists

Objectives—To evaluate the changes produced in both the isocapnic buffering and hypocapnic hyperventilation (HHV) phases of professional cyclists (n = 11) in response to endurance training, and to compare the results with those of amateur cyclists (n = 11). Methods—Each professional cyclist performed three laboratory exercise tests to exhaustion during the active rest (autumn: November), precompetition (winter: January), and competition (spring: May) periods of the sports season. Amateur cyclists only performed one exercise test during the competition period. The isocapnic buffering and HHV ranges were calculated during each test and defined as Vo2 and power output (W). Results—No significant differences were found in the isocapnic buffering range in each of the periods of the sports season in professional cyclists. In contrast, there was a significant reduction in the HHV range (expressed in W) during both the competition (p<0.01) and precompetition(p<0.05) periods compared with the rest period. On the other hand, a longer HHV range (p<0.01) was observed in amateur cyclists than in professional cyclists (whether this was expressed in terms of Vo2 or W). Conclusions—No change is observed in the isocapnic buffering range of professional cyclists throughout a sports season despite a considerable increase in training loads and a significant reduction in HHV range expressed in terms of power output.

Effects of an endurance cycling competition on resting serum insulin-like growth factor I (IGF-I) and its binding proteins IGFBP-1 and IGFBP-3

Objectives—To determine whether consecutive bouts of intense endurance exercise over a three week period alters serum concentrations of insulin-like growth factor I (IGF-I) and/or its binding proteins. Methods—Seventeen professional cyclists (mean (SEM) Vo2max, 74.7 (2.1) ml/kg/min; age, 27 (1) years) competing in a three week tour race were selected as subjects. Blood samples were collected at each of the following time points: t0 (control, before the start of competition), t1 (end of first week), and t3 (end of third week). Serum levels of both total and free IGF-I and IGF binding proteins 1 and 3 (IGFBP-1 and IGFBP-3) were measured in each of the samples. Cortisol levels were measured in nine subjects. Results—A significant (p<0.01) increase was found in total IGF-I and IGFBP-1 at both t1 and t3 compared with to (IGF-I: 110.9 (17.7), 186.8 (12.0), 196.9 (14.7) ng/ml at t0, t1, and t3 respectively; IGFBP-1: 54.6 (6.6), 80.6 (8.0), and 89.2 (7.9) ng/ml at t0, t1, and t3 respectively). A significant (p<0.01) decrease was noted in free IGF-I at t3 compared with both to and t1 (t0: 0.9 (0.1) ng/ml; t1: 0.9 (0.1) ng/ml; t3: 0.7 (0.1) ng/ml); in contrast, IGFBP-3 levels remained stable throughout the race. Conclusions—It would appear that the increase in circulating levels of both IGF-I and its binding protein IGFBP-1 is a short term (one week) endocrine adaptation to endurance exercise. After three weeks of training, total IGF-I and IGFBP-1 remained stable, whereas free IGF-I fell below starting levels.

Thyroid Hormone Levels during a 3-Week Professional Road Cycling Competition

Aims: The aim of this investigation was to examine the thyroid hormone levels of professional cyclists during a 3-week stage competition (Vuelta a España 1998). Methods: The study population was made up of 16 male cyclists from two world-leading professional teams. Four blood samples were drawn (between 07:00 and 09:00 a.m.) from each participant before and at the end of the 1st, 2nd and 3rd weeks of competition. 3,5,3′(-Triiodothyronine (T₃), free T₃ (FT₃), thyroxine (T₄), free T₄ (FT₄) and thyroid-stimulating hormone (TSH) were determined in each blood sample by radioimmunoassay. Results: Serum T₄, FT₄ and FT₃ levels showed a significant increase (p < 0.05) by the last week of competition while concentrations of TSH and T₃ remained unchanged. Conclusion: In conclusion, 3 weeks of competition provokes changes in basal thyroid hormone concentrations in professional road cyclists.

Mutations in the hereditary haemochromatosis gene HFE in professional endurance athletes

Background: Hereditary haemochromatosis, a disease that affects iron metabolism, progresses with a greater or lesser tendency to induce iron overload, possibly leading to severe organ dysfunction. Most elite endurance athletes take iron supplements during their active sporting life, which could aggravate this condition. Objective: To determine the prevalence and discuss potential clinical implications of mutations of HFE (the gene responsible for hereditary haemochromatosis) in endurance athletes. Methods: Basal concentrations of iron, ferritin, and transferrin and transferrin saturation were determined in the period before competition in 65 highly trained athletes. Possible mutations in the HFE gene were evaluated in each subject by extracting genomic DNA from peripheral blood. The restriction enzymes SnaBI and BclI were used to detect the mutations 845G→A (C282Y) and 187C→G (H63D). Results: Our findings indicate a high prevalence of HFE gene mutations in this population (49.2%) compared with sedentary controls (33.5%). No association was detected in the athletes between mutations and blood iron markers. Conclusions: The findings support the need to assess regularly iron stores in elite endurance athletes.

Lactic acidosis, potassium, and the heart rate deflection point in professional road cyclists

Objective: To determine the influence of lactic acidosis, the Bohr effect, and exercise induced hyperkalaemia on the occurrence of the heart rate deflection point (HRDP) in elite (professional) cyclists. Methods: Sixteen professional male road cyclists (mean (SD) age 26 (1) years) performed a ramp test on a cycle ergometer (workload increases of 5 W/12 s, averaging 25 W/min). Heart rate (HR), gas exchange parameters, and blood variables (lactate, pH, P50 of the oxyhaemoglobin dissociation curve, and K+) were measured during the tests. Results: A HRDP was shown in 56% of subjects at about 88% of their maximal HR (HRDP group; n = 9) but was linear in the rest (No-HRDP group; n = 7). In the HRDP group, the slope of the HR-workload regression line above the HRDP correlated inversely with levels of K+ at the maximal power output (r = −0.67; p<0.05). Conclusions: The HRDP phenomenon is associated, at least partly, with exercise induced hyperkalaemia.

Plasma Oxytocin during Intense Exercise in Professional Cyclists

Aims: This study was designed to explore the plasma oxytocin (OT) response to exercise until exhaustion in trained male cyclists. Methods: Twelve professional cyclists (EXP group; age: 26 ± 2 years; VO2max: 4,804 ± 549 ml) and 10 sedentary young men (CONT group; age: 23 ± 2 years; VO2max: 3,146 ± 602 ml) performed a maximal incremental exercise test on a cycle ergometer. Evaluation was made of the oxygen uptake (VO2) and concentrations of blood lactate and plasma OT immediately before, during and immediately after the tests, respectively. Results: Significant increases (p < 0.01) related to exercise were recorded in VO2 and lactate concentration within each group, while no such changes were observed in OT levels. OT values, on the other hand, were significantly lower (p < 0.01) in EXP than in CONT throughout the tests. Conclusion: It was concluded that plasma OT shows no response to graded exercise until exhaustion in professional cyclists.