Cycling Perfomance Physiology: An Analysis of What Makes a Good Rider
By William Misner, Ph.D.
This paper reports some, but not all, of the physical requirements determined to increase maximal cycling performance? The answer is complex when one seeks to determine what specific physiological characteristics change a good athlete into a great athlete. Those characteristics reviewed here are: maximal power output, sustained speed, body mass index, heart rate, blood lactate, red blood cell oxygen carrying capacity, exercise rate, training techniques, gear-cadence selection, breathing rate, serum mineral potassium changes, hormone changes, and nutrition protocol applications to achieve a desired performance effect.
What is required for establishing the One-Hour Cycling World Record? Padilla et al. set out to describe the physiological and aerodynamic characteristics and the preparation for a successful attempt to break the 1-hour cycling world record. AN ELITE PROFESSIONAL ROAD CYCLIST age 30, 6'2", 178 lbs, BMI 22.9, performed an incremental laboratory test to ASSESS MAXIMAL POWER OUTPUT (MAX) AND POWER OUTPUT (OBLA), ESTIMATED SPEED (VOBLA), and HEART RATE (HROBLA) AT THE ONSET OF BLOOD LACTATE ACCUMULATION (OBLA):
INCREMENTAL LABORATORY TEST PERFORMANCE LEVEL:
A-MAXIMAL POWER OUTPUT (MAX) - 572 Watts
B-POWER OUTPUT (OBLA) - 505 Watts
C-ESTIMATED SPEED (VOBLA} - 52.88 km/hour
D-HEART RATE @ ONSET OF BLOOD LACTATE (HROBLA) 183 beats/minute
INCREMENTAL VELODROME (CYCLING TRACK) TEST PERFORMANCE LEVEL
A-POWER OUTPUT OBLAVT1 - 500.6 Watts
B-ESTIMATED SPEED VOBLAVT1 - 52.7 km/h
C-HEART RATE @ ONSET OF BLOOD LACTATE HROBLAVT1 - 180 beats/minute
PHYSIOLOGICAL CAPACITY REQUIRED FOR THE ONE-HOUR WORLD RECORD
A-AVERAGE POWER OUTPUT - 509.5 Watts [HIGHER than predicted rate [497.25] based on VO2 Max suggesting the added benefit from motivation?]
Oh, is that all I need? No, intent motivation to go beyond predicted performance level might be required. This cyclist set a world record of 53,040 m, with an estimated average power output of 509.5 W. Based on direct laboratory data of the power vs. oxygen uptake relationship for this cyclist, this is slightly higher than the 497.25 Watts corresponding to his oxygen uptake at OBLA (5.65 l/min). The 1-hour cycling world record is the result of the interaction between physiological and aerodynamic characteristics; and 2) performance in this event can be partially predicted using mathematical models that integrate the principal performance-determining variables.  Further review suggests other factors may be observed when any athlete exposes themselves to performance-enhancing training protocols.
THE PHYSIOLOGICAL "FACTORS" REQUIRED FOR RACING FROM 1-100 HOURS
Male professional road cycling competitions last between 1 hour (e.g. the time trial in the World Championships) and 100 hours (e.g. the Tour de France). Although the final overall standings of a race are individual, it is undoubtedly a team sport. Professional road cyclists present with variable anthropometric values, but display impressive AEROBIC CAPACITIES [MAXIMAL POWER OUTPUT 370 TO 570 WATTS, MAXIMAL OXYGEN UPTAKE 4.4 to 6.4 L/min and POWER OUTPUT AT THE ONSET OF BLOOD LACTATE ACCUMULATION (OBLA) 300 TO 500 WATTS]. Because of the variable anthropometric characteristics, 'specialists' have evolved within teams whose job is to perform in different terrain and racing conditions. In this respect, POWER OUTPUTS RELATIVE TO MASS EXPONENTS OF 0.32 AND 1 SEEM TO BE THE BEST PREDICTORS OF LEVEL GROUND AND UPHILL CYCLING ABILITY, RESPECTIVELY. However, TIME TRIAL SPECIALISTS HAVE BEEN SHOWN TO MEET REQUIREMENTS TO BE TOP COMPETITORS IN ALL TERRAIN (LEVEL AND UPHILL) AND CYCLING CONDITIONS (INDIVIDUALLY AND IN A GROUP). Based on competition heart rate measurements, time trials are raced under steady-state conditions, the shorter time trials being raced at average intensities close to OBLA (approximately 400 to 420 WATTS), with the longer ones close to the individual lactate threshold (LT, approximately 370 to 390 WATTS). Mass-start stages, on the other hand, are raced at low mean intensities (approximately 210 WATTS for the flat stages, approximately 270 WATTS for the high mountain stages), but are characterized by their intermittent nature, with cyclists spending on average 30 to 100 minutes at, and above LT, and 5 to 20 minutes at, and above OBLA. 
RED BLOOD CELL TURNOVER RATE HIGH IN ELITE ATHLETES [MCV HIGHER]
Athletes during endurance events require rapid uptake of oxygen, the ability of red blood cells (RBC) to move through capillaries may limit performance imposing high turnover rate in red blood cells. Using ektacytometry, researchers  determined whether RBC deformability (RCD) differed between elite road cyclists (n = 9) and sedentary controls (n = 5). Density profiles and standard hematological measurements were also performed. The deformability index (DI) was higher in the cyclists (0.723 - 0.027) compared with that in controls 0.619 - 0.040. Cyclists also had a larger percentage of low-density RBCs, and MEAN CELL VOLUME (MCV) WAS ALSO HIGHER. MEAN CORPUSCULAR VOLUME (MCV) 80 - 97 fl is normal reference range. Elite cyclists tend toward "HIGH" [H] or above normal reference range. MCV is the size or volume of an average erythrocyte. High level may indicate pernicious anemia, folic acid anemia, and other anemias. On the other hand, low level indicates parasites, carcinoid syndrome, iron anemia, hypochlorhydria, B6 anemia, rheumatoid arthritis, and toxic effects of lead.  These findings are indicative of a larger proportion of "young" RBCs in the blood of elite cyclists and provide further evidence that the turnover of RBCs in endurance athletes is HIGHER than in the general population. With a younger more deformable RBC population and providing the destruction does not exceed replacement, performance potential should be enhanced. Furthermore, examinations of factors that contribute to increased RBC turnover in athletes helps explain some of the complex mechanisms that induce RBC aging.
ALTITUDE ACCLIMATIZATION LIVE-HIGH TRAIN-LOW IMPROVES RED BLOOD CELL PROFILE AND PERFORMANCE
Acclimatization to moderate high altitude accompanied by training at low altitude (LIVING HIGH-TRAINING LOW) has been shown to improve sea level endurance performance in accomplished, but not elite, runners. Whether elite athletes, who may be closer to the maximal structural and functional adaptive capacity of the respiratory (i.e., oxygen transport from environment to mitochondria) system, may achieve similar performance gains is unclear. To answer this question, we studied 14 elite men and 8 elite women before and after 27 days of living at 2,500 m while performing high-intensity training at 1,250 m. The altitude sojourn began 1 wk after the USA Track and Field National Championships, when the athletes were close to their season's fitness peak. Sea level 3,000-m time trial performance was significantly improved by + 1.1%. One-third of the athletes achieved personal best times for the distance after the altitude training camp. The improvement in running performance was accompanied by a 3% improvement in maximal oxygen uptake (mean improvement was 72.1 to 74.4 ml kg1 min1). CIRCULATING ERYTHROPOIETIN LEVELS WERE NEAR DOUBLE INITIAL SEA LEVEL VALUES 20 H AFTER ASCENT (mean averages of 8.5 to 16.2 IU/ml). Soluble transferrin receptor levels were significantly elevated on the 19th day at altitude, confirming a STIMULATION OF ERYTHROPOIESIS (mean increase of 2.1 to 2.5 g/ml). HEMOBGLOBIN concentration measured at sea level increased 1 g/dl over the course of the camp (mean average of 13.3 to 14.3 g/dl). Researchers concluded that 4 weeks of acclimatization to moderate altitude, accompanied by high-intensity training at low altitude, improves sea level endurance performance even in elite runners. Both the mechanism and magnitude of the effect appear similar to that observed in less accomplished runners, even for cyclists who may have achieved near maximal oxygen transport capacity for humans. 
RED BLOOD PROFILES ARE COMPROMISED OR ENHANCED BY INTENSE MAXIMAL VO2 EXERCISE
The extreme thinness of the pulmonary blood-gas barrier results in high mechanical stresses in the capillary wall when the capillary pressure rises during exercise. Research has previously shown that, IN ELITE CYCLISTS, 6-8 MIN OF MAXIMAL EXERCISE increase blood-gas barrier permeability and RESULT IN HIGHER CONCENTRATIONS OF RED BLOOD CELLS, total protein, and leukotriene B4 in BRONCHOALVEOLAR LAVAGE (BAL) fluid compared with results in sedentary controls. To test the hypothesis that stress failure of the barrier only occurs at the highest level of exercise, RESERCHERS PERFORMED BRONCHOALVEOLAR LAVAGE (BAL) IN SIX HEALTHY ATHLETES AFTER 1 HOUR OF EXERCISE AT 77% OF MAXIMAL O2 CONSUMPTION. Controls were eight normal nonathletes who did not exercise before BAL. In contrast with previous research, they did not find higher concentrations of red blood cells, total protein, and leukotriene B4 in the exercising athletes compared with control subjects. However, higher concentrations of surfactant apoprotein A and a higher surfactant apoprotein A-to-phospholipid ratio were observed in the athletes performing prolonged exercise, compared with both the controls and the athletes from our previous study. These results suggest that, in elite athletes, the integrity of the blood-gas barrier is altered only at extreme levels of exercise.  If a cyclist wishes to influence red blood cell O-2 carrying capacity, 6-8 minutes bouts of intense 100% VO2 Max rate exercise must by employed in periodic training fashion.
HOW EXTREME EXERCISE INFLUENCES HEMATOCRIT [EPO] OUTCOME
Knowledge is sparse about the extent of POTENTIAL DEHYDRATION due to prolonged strenuous cycling and its hematological acute effects on the HEMATOCRIT (HCT) in study populations credibly not taking any kind of doping. With increasing training load levels of HEMATOCRIT (HCT) and HEMOGLOBIN (HB) decrease in amateurs and professionals as a long-term consequence due to EXPANDED PLASMA VOLUME (PV). On a short-term basis, however, counteracting dehydration potentially brought about by endurance exercise may cause a rise in HEMATOCRIT (HCT) bringing competitive cyclists into conflict with the current condition regulations and Hct cut-off of 50 % set by the International Cycling Union (UCI) in its fight against ERYTHROPOIETIN (rhEPO) doping. On the other hand adequate and sufficient fluid substitution being substantial for a successful endurance performance should prevent any pronounced HEMATOCRIT (HCT) rises. To study the hematological acute effects of prolonged strenuous cycling researchers measured Hct, Hb, red blood cell (RBC) count and plasma protein in a reliably 'clean' population of 38 well-trained male amateur cyclists before, immediately after and one day after an extraordinary ultramarathon. The PRE-RACE LEVELS of HEMATOCRIT (HCT), HEMOGLOBIN (Hb) and RBC count were placed in the LOWER RANGE OF NORMAL DISTRIBUTION and well below the Hct cut-off limit of the UCI. IMMEDIATELY POST-EXERCISE THE MEAN LEVELS OF HCT, HB, RBC COUNT AND PROTEIN REMAINED UNCHANGED. ONE DAY AFTER A RACE, FOUR PARAMETERS SIGNIFICANTLY DROPPED:
B-HB -6.7 %
D-SERUM PROTEIN -9.9%
This indicates a marked increase in post-exercise EXPANDED PLASMA VOLUME (PV). The calculated percentage increase in EXPANDED PLASMA VOLUME (PV) was + 11.9%! No evidence for coexisting exercise-induced hemolysis was found. Our study shows that in "clean, rhEPO-free" amateur cyclists who involve in strenuous marathon cycling the hematological short-term effects of extraordinary marathon cycling consist in considerable EXPANDED PLASMA VOLUME (PV) expansion making HEMATOCRIT (HCT) values fall on the following day. The findings - gained from amateurs though - suggest that despite all its disadvantages the UCI Hct cut-off represents an appropriate means to discourage from excessive rhEPO doping at least as long as the available direct methods for detecting this kind of misuse are not yet applied by the international sports federations. 
A TRAINING "TECHNIQUE" THAT INCREASES EPO
Twelve subjects without and ten subjects with diving experience performed short diving-related interventions. After labeling of erythrocytes, scintigraphic measurements were continuously performed during these interventions. All interventions elicited a graduated and reproducible splenic contraction, depending on the type, severity, and duration of the interventions. The splenic contraction varied between ~10% for "apnea" (breath holding for 30 s) and "cold clothes" (cold and wet clothes applied on the face with no breath holding for 30 s) and ~30-40% for "simulated diving" (simulated breath-hold diving for 30 s), "maximal apnea" (breath holding for maximal duration), and "maximal simulated diving" (simulated breath-hold diving for maximal duration). The strongest interventions (simulated diving, maximal apnea, and maximal simulated diving) elicited modest but significant increases in hemoglobin concentration (0.1-0.3 mmol/l) and hematocrit (0.3-1%). By an indirect method, the splenic venous hematocrit was calculated to 79%. No major differences were observed between the two groups. The splenic contraction should, therefore, be included in the diving response on equal terms with bradycardia, decreased peripheral blood flow, and increased blood pressure.  A +1% hematocrit gain may result from frequent hypoxic breath holding interventions ranging from 30 seconds to maximal duration. 
TRAINING TECHNIQUES FOR MAXIMAL PERFORMANCE VS OVERTRAINING
To study the cumulative effects of exercise stress and subsequent recovery on performance changes and fatigue indicators, the training of eight endurance cyclists was systematically controlled and monitored for a six-week period.
Subjects completed 2 weeks each of:
[A] NORMAL TRAINING (N)
[B] INTENSIFIED TRAINING (ITP)
[C] RECOVERY TRAINING (R)
A significant DECLINE in maximal power output average of 338 watts to 319 watts and a significant INCREASE in time to complete a simulated TIME-TRIAL average 59.4 to 65.3 minutes occurred after INTENSIFIED TRAINING in conjunction with a 29% INCREASE IN GLOBAL MOOD DISTURBANCE. The decline in performance was associated with a 9.3% reduction in maximal heart rate, a 5% reduction in maximal oxygen uptake and an 8.6% increase in perception of effort. Despite the large reductions in performance no changes were observed in substrate utilization, cycling efficiency, lactate concentration, plasma urea, ammonia, and catecholamine concentration. These findings indicate that a state of overreaching can already be induced after 7 days of intensified training with limited recovery.  A combinative rest must follow periodic intensity; normal training [under 80% VO2 Max rate] in order to attain rebound recovery.
TRAINING RATE DUPLICATES ALTITUDE HYPOXIA FOR PERFORMANCE GAINS
The effect of hypoxia on the response to interval exercise was determined in EIGHT ELITE FEMALE CYCLISTS during two interval sessions: a sustained 3 - 10-min endurance set (5-min recovery) and a repeat sprint session comprising three sets of 6 - 15-s sprints (work-to-relief ratios were 1:3, 1:2, and 1:1 for the 1st, 2nd, and 3rd sets, respectively, with 3 min between each set). During exercise, cyclists selected their maximum power output and breathed either atmospheric air (normoxia, 20.93% O2) or a hypoxic gas mix (hypoxia, 17.42% O2). POWER OUTPUT WAS LOWER IN HYPOXIA VS. NORMOXIA THROUGHOUT THE ENDURANCE SET (mean of 244 vs. 226, compared to 234 vs. 221, and 235 vs. 221 Watts for 1st, 2nd, and 3rd sets, respectively but was lower only in the latter stages of the second and third sets of the sprints (mean of 452 vs. 429 and 403 vs. 373 Watts, respectively. Hypoxia lowered blood O2 saturation during the endurance set (mean of 92.9 vs. 95.4% but not during repeat sprints. The researchers concluded that, when elite cyclists select their maximum exercise intensity, BOTH 10 MINUTES SUSTAINED and SHORT-TERM OF 15 SECONDS POWER are impaired during hypoxia, which SIMULATED MODERATE (~2,100 m) ALTITUDE. 
AEROBIC AND STRENGTH TRAINING INCREASE PERFORMANCE OUTCOME
Researchers investigated the effects of replacing a portion of ENDURANCE TRAINING Vs STRENGTH TRAINING ON EXERCISE PERFORMANCE, 14 competitive cyclists were divided into an experimental (E; n = 6) and a control (C; n = 8) group. Both groups received a training program of 9 weeks. The total training volume for both groups was the same [Experimental: 8.8 (1.1) h/week; Control: 8.9 (1.7) h/week], but 37% OF TRAINING FOR EXPERIMENTAL CONSISTED OF EXPLOSIVE-TYPE STRENGTH TRAINING, whilst CONTROL RECEIVED ENDURANCE TRAINING ONLY. Simulated time trial performance (TT), SHORT-TERM PERFORMANCE (STP), MAXIMAL WORKLOAD (Wmax) and GROSS (GE) and DELTA EFFICIENCY (DE) were measured before, after 4 weeks and at the end of the training program (9 weeks). NO SIGNIFICANT GROUP-BY-TRAINING EFFECTS FOR THE MARKERS OF ENDURANCE PERFORMANCE (TT and Wmax) were found after 9 weeks, although after 4 weeks, these markers had only increased in the Experimental Group. SHORT-TERM PERFORMANCE (STP) decreased in Control Group, whereas no changes were observed in the Experimental Group. For DE, a significant group-by-training interaction was found, and for GROSS EFFICIENCY (GE) the group-by-training interaction was not significant. They concluded that replacing a portion of endurance training by 37% explosive strength training prevents a decrease in SHORT-TERM PERFORMANCE (STP) without compromising gains in endurance performance of trained cyclists. 
WORKLOAD DIFFERENCES BETWEEN PROFESSIONAL AND AMATEUR CYCLISTS
Researchers analyzed the kinetics of OXYGEN UPTAKE (VO2) in professional road cyclists during a ramp cycle ergometer test and to compare the results with those derived from well-trained amateur cyclists. 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 VO2: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). In the PROFESSIONAL CYCLISTS group, the mean slope (Delta VO(2):Delta W) of the VO(2):Watts relationship decreased significantly 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 were found between phases I and II in AMATEUR group, whereas Delta VO(2):Delta W significantly increased in phase III, 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 PROFESSIONAL CYCLISTS group than in the AMATEUR CYCLIST group. 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.  This may suggest that professional cyclists impose a harder training requirement, which imposes greater fitness adaptation.
GEAR SELECTION AND PEDAL RATE INFLUENCE GROSS EFFICIENCY RESULTING IN PERFORMANCE GAIN
Cyclists seek to maximize performance during competition, and gross efficiency is an important factor affecting performance. Gross efficiency is itself affected by pedal rate. Thus, it is important to understand factors that affect freely chosen pedal rate. CRANK INERTIAL LOAD VARIES GREATLY DURING ROAD CYCLING BASED ON THE SELECTED GEAR RATIO. Nevertheless, the possible influence of crank inertial load on freely chosen pedal rate and gross efficiency has never been investigated. This study tested the hypotheses that during cycling with sub-maximal work rates, a considerable increase in crank inertial load would cause (1) freely chosen pedal rate to increase, and as a consequence, (2) gross efficiency to decrease. Furthermore, that it would cause (3) peak crank torque to increase if a constant pedal rate was maintained. Subjects cycled on a treadmill at 150W and 250W, with low and high crank inertial load, and with preset and freely chosen pedal rate. Freely chosen pedal rate was higher at high compared with low crank inertial load. Notably, the change in crank inertial load affected the freely chosen pedal rate as much as did the 100W increase in work rate. Along with freely chosen pedal rate being higher, gross efficiency at 250W was lower during cycling with high compared with low crank inertial load. Peak crank torque was higher during cycling at 90rpm with high compared with low crank inertial load. Possibly, the subjects increased the pedal rate to compensate for the higher peak crank torque accompanying cycling with high compared with low crank inertial load. 
CADENCE PREFERENCES OF PROFESSIONAL CYCLISTS
Researchers also evaluated the preferred cycling cadence of professional riders during competition. They measured the cadence of seven professional cyclists (28 +/- 1 yr) during 3-wk road races (Giro d'Italia, Tour de France, and Vuelta a Espana) involving three main competition requirements: UPHILL CYCLING (high mountain passes of approximately 15 km, or HM); INDIVIDUAL TIME TRIALS of approximately 50 km on level ground (TT); and FLAT, LONG (approximately 190 km) GROUP STAGES (F). HEART RATE (HR) data were also recorded, as an indicator of exercise intensity during HM, TT, and F. MEAN CADENCE WAS SIGNIFICANTLY LOWER DURING UPHILL CYCLING (69.6-72.4 rpm) than either FLAT STAGES [88.3-90.3 rpm] and TIME TRIAL [91.1-93.7 rpm]. HEART RATE was similar during HIGH MOUNTAIN [153-161 bpm] and TIME TRIAL [155-161 bpm] and in both cases higher than during FLAT LONG GROUP STAGES [122-126 bpm]. During both FLAT and TIME TRIALS, professional riders spontaneously adopt higher cadences (around 90 rpm) than those previously reported in the majority of laboratory studies as being the most economical. In contrast, during UPHILL CYCLING they seem to adopt a more economical pedaling rate (approximately 70 rpm), possibly as a result of the specific demands of this competition phase. 
BREATHING RATE INFLUENCES FATIGUE AND PERFORMANCE IN CYCLISTS?
The normal respiratory muscle effort at maximal exercise requires a significant fraction of cardiac output and causes leg blood flow to fall. Researchers questioned whether the high levels of respiratory muscle work experienced in heavy exercise would affect performance. Seven male cyclists [maximal O2 consumption (O2) 58-69 ml kg1 min1] each completed 11 randomized trials on a cycle ergometer at a workload requiring 90% maximal VO2.
RESPIRATORY MUSCLE WORK WAS:
A-DECREASED (UNLOADING)-->Time to exhaustion was increased with unloading in 76% of the trials by an average of 0.9-1.7 1.3 min or 9-19%.
B-INCREASED (LOADING)-->decreased with loading in 83% of the trials by an average of 0.4-1.6 minutes or 12-18%
C-UNCHANGED (CONTROL)-->A & B were compared to control
Respiratory muscle unloading during exercise reduced O2, caused hyperventilation, and reduced the rate of change in perceptions of respiratory and limb discomfort throughout the duration of exercise. These findings demonstrate that the work of breathing normally incurred during sustained, heavy-intensity exercise (90% O2) has a significant influence on exercise performance. They speculated that this effect of the normal respiratory muscle load on performance in trained male cyclists is due to the associated reduction in leg blood flow, which enhances both the onset of leg fatigue and the intensity with which both leg and respiratory muscle efforts are perceived. 
HIGH POTASSIUM AT 88% MAX HEART RATE IN SOME, NOT ALL PRO-CYCLISTS
Researchers set out to determine the influence of lactic acidosis, the Bohr effect, and exercise induced hyperkalaemia [high potassium] on the occurrence of the heart rate deflection point (HRDP) in elite (professional) cyclists. 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, P(50) of the oxyhemoglobin dissociation curve, and K(+)) were measured during the tests. A HEART RATE DEFLECTION POINT [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 heart rate deflection point [HRDP] group, the slope of the HR-workload regression line above the HRDP correlated inversely with levels of potassium [K(+)] at the maximal power output.The heart rate deflection point [HRDP] phenomenon is associated, at least partly, with exercise-induced hyperkalaemia. 
MALE ENDURANCE ATHLETES: SPERM ANALYSIS VS HORMONAL PROFILE
Researchers studied the effects of endurance exercise on male reproductive function (sex hormones and seminograms). Professional cyclists [n = 12; mean age 24 - 2 (SD) yr], elite triathletes (n = 9; 26 - 3 yr), recreational marathon runners (n = 10; 32 - 6 yr), and sedentary subjects (control group; n = 9; 30 - 4 yr) were selected as subjects. For each group, the following parameters were measured three times during the sports season (training period: winter; competition period: spring; resting period: fall): percentage of body fat, hormonal profile (resting levels of follicle-stimulating hormone, luteinizing hormone, total and free testosterone, and cortisol), and seminograms (quantitative parameters: sperm volume and sperm count; qualitative parameters: sperm motility and morphology). The following comparisons were made in the measured parameters: 1) within groups (longitudinal design) and 2) between groups in each of the three periods (cross-sectional design) and over time (mixed design). In addition, both the volume and the intensity of training of each subject during the season (except for the control group) were quantified. Despite significant differences in training characteristics and in body fat percent, in general NO SIGNIFICANT DIFFERENCES WERE FOUND IN HORMONAL PROFILES OR IN SEMEN CHARACTERISTICS BETWEEN OR WITHIN GROUPS. A lower sperm motility (ranges +26.7 to +65.7%), however, was observed in the cyclists during the competition period when compared either with the other groups during this same period or with themselves during the other two periods of study. In any case, the later phenomenon was attributed to physical factors associated with cycling, such as mechanical trauma to the testis and/or increased gonadal temperature. In conclusion, our findings suggest that endurance exercise does not adversely affect the hypothalamic-pituitary-testis axis.  Hormones in male endurance subjects are NOT adversely effected by intense training protocols, though male cyclists may need to consider compensatory sperm motility factors such as a saddle which permits less pressure on prostate area.
HORMONE CHANGES IN PRO RACERS: CORTISOL, TESTOSTERONE, AND 6-SULPHATOXYMELATONIN INCREASE AFTER RACE BUT DECREASE LATER
One study evaluated the hormonal response to strenuous endurance exercise performed by elite athletes. Nine professional cyclists (mean (SD) age 28 (1) years; mean (SD) VO(2)MAX 75.3 (2.3) ml/kg/min) who participated in a three week tour race (Vuelta a Espana 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 t(0) (before the competition), t(1) (end of first week), t(2) (end of second week), and t(3) (end of third week). Urine samples of aMT6s were also evaluated in the evening at t(0), t(1), t(2), and t(3). MEAN URINARY 6-SULPHATOXYMELATONIN (AMT6S) LEVELS HAD INCREASED SIGNIFICANTLY DURING THE DAY AFTER EACH STAGE (1091 (33) v 683 (68) ng/ml at t(1); 955 (19) v 473 (53) ng/ml at t(2); 647 (61) v 337 (47) ng/ml at t(3)). Both morning and evening aMT6s levels decreased significantly during the study. A SIMILAR PATTERN WAS OBSERVED FOR MORNING SERUM LEVELS OF CORTISOL AND TESTOSTERONE. 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. 
PROLONGED ENDURANCE STAGE-RACING INCREASES 3 THYROID HORMONES
Other researchers examined thyroid hormone levels of professional cyclists during a 3-week stage competition (Vuelta a Espana 1998). 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 (T(3)), free T(3) (FT(3)), thyroxine (T(4)), free T(4) (FT(4)) and thyroid-stimulating hormone (TSH) were determined in each blood sample by radioimmunoassay. SERUM T(4), FT(4) AND FT(3) LEVELS SHOWED A SIGNIFICANT INCREASE by the last week of competition while concentrations of TSH and T(3) remained unchanged. In conclusion, 3 weeks of competition provokes changes in basal thyroid hormone concentrations in professional road cyclists. 
NUTRITION PRACTICES OF ELITE CYCLISTS
The nutritional requirements of the training and competition programs of elite endurance cyclists are challenging. Notwithstanding the limitations of dietary survey techniques, studies of high-level male road cyclists provide important information about nutrient intake and food practices during training and major stage races. Typically, male cyclists undertaking intensive training programs report a high-energy intake (> or = 250 kJ/kg/day) and carbohydrate (CHO) intakes of 8 to 11 g/kg/day. Intakes of protein and micronutrients are likely to meet Recommended Dietary Intake levels, because of high-energy intakes. Data on female cyclists are scarce. Stage racing poses an increased requirement for energy and CHO, with daily energy expenditure often exceeding 25 MJ. This must be achieved in the face of practical constraints on the time available for eating, and the suppression of appetite after exhausting exercise. However, studies show that male cyclists riding for professional teams appear to meet these challenges, with the assistance of their medical/scientific support crews. Current dietary practices during cycle tours appear to favor greater reliance on pre-stage intake and post-stage recovery meals to achieve nutritional goals. Recent reports suggest that current riding tactics interfere with previous practices of consuming substantial amounts of fluid and CHO while cycling. Further study is needed to confirm these practices, and to investigate whether these or other dietary strategies produce optimal cycling performance. Other issues that should receive attention include dietary practices of female cyclists, beliefs and practices regarding bodyweight control among cyclists, and the use of supplements and sports foods. 
OTHER NUTRITIONAL PROTOCOLS MAY ENHANCE PERFORMANCE
A nutritional protocol has been designed for enhancing lean muscle mass for endurance performance outcome during strength phase training  and another nutritional protocol has been designed for enhancing EPO during endurance and sprint training.  To achieve optimal Body Mass Index of lean muscle mass to fat mass, a nutritional dietary protocol has been designed. [23, 24, 25]
To advance performance outcome, an inherited physique must be exposed to stairstep exercise stress in periodic fashion. Properly ordered training demands increase prolonged endurance rate, short-term muscle torque sprint, higher oxygen volume exchange, hormone adaptations, lactate pH response, and variations in serum mineral exchange. Nutritional interventions must be considered to regenerate repletion of both macronutrients and micronutrients losses during extreme energy output. Practical application of all these principles may result in changing a good rider into a great one.
 Sabino Padilla, I'igo Mujika, Francisco Angulo, and Juan Jose Goiriena Scientific approach to the 1-h cycling world record: a case study J Appl Physiol 2000 89: 1522-1527.
 Mujika I, Padilla S. Physiological and performance characteristics of male professional road cyclists. Sports Med. 2001;31(7):479-87.
 John A. Smith, David T. Martin, Richard D. Telford, and Samir K. Ballas
Greater erythrocyte deformability in world-class endurance athletes
Am J Physiol Heart Circ Physiol 1999 276: H2188-H2193.
 CLINICAL NUTRITION FOR THE BALANCED BODY[2nd Edition] Reprinted by permission of Dr. John A. Allocca, Sc.D., Ph.D., C.C.N. @:
Published by Allocca Biotechnology, Inc. URL: http://www.allocca.com Distributed by: International and American Associations of Clinical Nutritionists (IAACN) Phone: (972) 250-2829 URL: http://www.iaacn.org
 James Stray-Gundersen, Robert F. Chapman, and Benjamin D. Levine.
"Living high-training low" altitude training improves sea level performance in male and female elite runners. J Appl Physiol 2001 91: 1113-1120.
 Susan R. Hopkins, Robert B. Schoene, William R. Henderson, Roger G. Spragg, and John B. West Sustained submaximal exercise does not alter the integrity of the lung blood-gas barrier in elite athletes J Appl Physiol 1998 84: 1185-1189.
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 The human spleen as an erythrocyte reservoir in diving-related interventions Kurt Espersen, Hans Frandsen, Torben Lorentzen, Inge-Lis Kanstrup, and Niels J. Christensen J Appl Physiol 2002;92 2071-2079.
 Shona L Halson, Matthew W Bridge, Romain Meeusen, Bart Busschaert, Michael Gleeson, David A Jones, and Asker E Jeukendrup. Time course of performance changes and fatigue markers during intensified training in cyclists Articles in PresS: J Appl Physiol published April 5, 2002, 10.1152/japplphysiol.01164.2001
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Impaired interval exercise responses in elite female cyclists at moderate simulated altitude
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 Bastiaans JJ, van Diemen AB, Veneberg T, Jeukendrup AE. The effects of replacing a portion of endurance training by explosive strength training on performance in trained cyclists. Eur J Appl Physiol. 2001 Nov;86(1):79-84.
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 Craig A. Harms, Thomas J. Wetter, Claudette M. St. Croix, David F. Pegelow, and Jerome A. Dempsey Effects of respiratory muscle work on exercise performance J Appl Physiol 2000 89: 131-138.
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 Alejandro Luca, Jos L. Chicharro, Margarita Prez, Luis Serratosa, Fernando Bandrs, and Julio C. Legido. Reproductive function in male endurance athletes: sperm analysis and hormonal profile J Appl Physiol 1996 81: 2627-2636.
 Lucia A, Diaz B, Hoyos J, Fernandez C, Villa G, Bandres F, Chicharro JL. Hormone levels of world class cyclists during the Tour of Spain stage race. Br J Sports Med. 2001 Dec;35(6):424-30.
 Chicharro JL, Hoyos J, Bandres F, Terrados N, Fernandez B, Lucia A. Thyroid Hormone Levels during a 3-Week Professional Road Cycling Competition. Horm Res. 2001;56(5-6):159-64.
 Burke LM. Nutritional practices of male and female endurance cyclists. Sports Med. 2001;31(7):521-32.
 INTERVENTIONS FOR ENHANCING LEAN MUSCLE MASS GAIN AND FAT MASS LOSS DURING STRENGTH OR SPEED TRAINING PROTOCOLS Bill Misner Ph.D., WEIGHT MANAGEMENT SECTION----->Natural Anabolic Hormone Interventions @:
 ERYTHROPOIETIN[EPO]: NUTRITIONAL AND TRAINING INTERVENTIONS FOR INCREASING EPO, Bill Misner Ph.D., ENDURANCE LIBRARY-->DIET FOR PERFORMANCE AND HEALTH @:
 What is Body Mass Index (BMI) and what is its practical application in terms of endurance performance? Bill Misner Ph.D., ENDURANCE LIBRARY--->WEIGHT MANAGEMENT @:
 Weight Management Position Paper, Bill Misner Ph.D., ENDURANCE LIBRARY--->WEIGHT MANAGEMENT @:
 Weight Management: a prominent component of health and fitness, Bill Misner Ph.D., ENDURANCE LIBRARY--->WEIGHT MANAGEMENT @:
*Bill Misner Ph.D is the Director of Research & Product Development for Hammer Nutrition, LTD.