Physiological and Mechanical Indices Serving the New Cross-Country Olympic Mountain Bike Performance

Objectives: To identify relevant physiological, mechanical, and strength indices to improve the evaluation of elite mountain bike riders competing in the current Cross-Country Olympic (XCO) format. Methods: Considering the evolution of the XCO race format over the last decade, the present testing protocol adopted a battery of complementary laboratory cycling tests: a maximal aerobic consumption, a force–velocity test, and a multi-short-sprint test. A group of 33 elite-level XCO riders completed the entire testing protocol and at least 5 international competitions. Results: Very large correlations were found between the XCO performance and maximal aerobic power output (r = .78; P < .05), power at the second ventilation threshold (r = .83; P < .05), maximal pedaling force (r = .77; P < .05), and maximum power in the sixth sprint (r = .87; P < .05) of the multi-short-sprint test. A multiple regression model revealed that the normalized XCO performance was predicted at 89.2% (F3,29 = 89.507; r = .95; P < .001) by maximum power in the sixth sprint (β = 0.602; P < .001), maximal pedaling rate (β = 0.309; P < .001), and relative maximal aerobic power output (β = 0.329; P < .001). Discussion: Confirming our expectations, the current XCO performance was highly correlated with a series of physiological and mechanical parameters reflecting the high level of acyclic and intermittent solicitation of both aerobic and anaerobic metabolic pathways and the required qualities of maximal force and velocity. Conclusion: The combination of physiological, mechanical, and strength characteristics may thus improve the prediction of elite XCO cyclists’ performance. It seems of interest to evaluate the ability to repeatedly produce brief intensive efforts with short active recovery periods.

Divergent endothelial function but similar platelet microvesicle responses following eccentric and concentric cycling at a similar aerobic power output

Endothelial function and microvesicle concentration changes after acute bouts of continuous eccentric exercise have not been assessed previously nor compared with concentric exercise at similar aerobic power outputs. This method of training may be useful among some clinical populations, but acute responses are not well described. As such, 12 healthy males completed 2 experimental sessions of either 45 min of eccentric or concentric cycling at a matched aerobic power output below the ventilatory threshold. Brachial artery vascular function was assessed throughout 5 min of forearm ischemia and 3 min thereafter, before and at 5 and 40 min of recovery following each exercise session [flow-mediated dilation (FMD)]. Venous blood samples were acquired before each vascular function assessment. FMD significantly decreased after eccentric cycling by 40 min of recovery ( P < 0.05), but was unaltered after concentric exercise. No differences in peak hyperemic blood flow velocity occurred neither between modalities nor at any time point ( P > 0.05). Platelet-derived microvesicles increased by ~20% after both exercise modalities ( P < 0.05) while endothelial-derived microvesicles were unchanged ( P > 0.05). Moderate relationships with cardiac output, a surrogate for shear stress, and norepinephrine were apparent ( P < 0.05), but there were no relationships with inflammatory or acute phase proteins. In summary, eccentric endurance exercise induced macrovascular endothelial dysfunction; however, endothelial activation determined by endothelial microvesicles did not occur suggesting that this modality may induce oxidative stress but no significant endothelial damage. In addition, the increase in platelet microvesicle concentrations may induce beneficial microvascular adaptations as suggested by previous research. NEW & NOTEWORTHY Continuous eccentric cycling exercise induces substantial skeletal muscle, tendon, and bone strain providing a potentially beneficial stimulus among clinical populations. This modality also induces temporary endothelial dysfunction but no apparent damage or activation of the endothelium indicated by microvesicle production, whereas proangiogenic platelet microvesicles are released similarly following both concentric and eccentric cycling and may relate to the shear stress and catecholamine response to exercise.

Similar substrate oxidation rates in concentric and eccentric cycling matched for aerobic power output

This study investigated substrate oxidation in concentric and eccentric cycling matched for aerobic power output in the postprandial state. Energy expenditure, respiratory exchange ratio, and fat and carbohydrate oxidation rates were measured at rest and after 15, 30, and 45 min of eccentric and concentric cycling in 12 men. Absolute and relative aerobic power output and energy expenditure were similar during concentric and eccentric exercise. No effect of exercise modality was observed for substrate metabolism.

Effects of workload level on muscle recruitment in cycling

Purpose. Despite the volume of studies addressing muscle activation during pedaling, it is unclear whether changes in workload level during cycling could dictate motor unit recruitment. The present study investigated the frequency content of lower limb muscle activation during submaximal workloads. Methods. Twelve male competitive cyclists pedaled at three workload levels: (1) maximum aerobic power output (PO

The Cycling Physiology of Miguel Indurain 14 Years After Retirement

Age-related fitness declines in athletes can be due to both aging and detraining. Very little is known about the physiological and performance decline of professional cyclists after retirement from competition. To gain some insight into the aging and detraining process of elite cyclists, 5-time Tour de France winner and Olympic Champion Miguel Indurain performed a progressive cycle-ergometer test to exhaustion 14 y after retirement from professional cycling (age 46 y, body mass 92.2 kg). His maximal values were oxygen uptake 5.29 L/min (57.4 mL · kg−1 · min−1), aerobic power output 450 W (4.88 W/kg), heart rate 191 beats/min, blood lactate 11.2 mM. Values at the individual lactate threshold (ILT): 4.28 L/min (46.4 mL · kg−1 · min−1), 329 W (3.57 W/kg), 159 beats/min, 2.4 mM. Values at the 4-mM onset of blood lactate accumulation (OBLA): 4.68 L/min (50.8 mL · kg−1 · min−1), 369 W (4.00 W/kg), 170 beats/min. Average cycling gross efficiency between 100 and 350 W was 20.1%, with a peak value of 22.3% at 350 W. Delta efficiency was 27.04%. Absolute maximal oxygen uptake and aerobic power output declined by 12.4% and 15.2% per decade, whereas power output at ILT and OBLA declined by 19.8% and 19.2%. Larger declines in maximal and submaximal values relative to body mass (19.4–26.1%) indicate that body composition changed more than aerobic characteristics. Nevertheless, Indurain’s absolute maximal and submaximal oxygen uptake and power output still compare favorably with those exhibited by active professional cyclists.

Effects of 2 different prior endurance exercises on whole-body fat oxidation kinetics: light vs. heavy exercise

This study aimed to compare the effects of 2 different prior endurance exercises on subsequent whole-body fat oxidation kinetics. Fifteen men performed 2 identical submaximal incremental tests (Incr2) on a cycle ergometer after (i) a ∼40-min submaximal incremental test (Incr1) followed by a 90-min continuous exercise performed at 50% of maximal aerobic power-output and a 1-h rest period (Heavy); and (ii) Incr1 followed by a 2.5-h rest period (Light). Fat oxidation was measured using indirect calorimetry and plotted as a function of exercise intensity during Incr1 and Incr2. A sinusoidal equation, including 3 independent variables (dilatation, symmetry and translation), was used to characterize the fat oxidation kinetics and to determine the intensity (Fatmax) that elicited the maximal fat oxidation (MFO) during Incr. After the Heavy and Light trials, Fatmax, MFO, and fat oxidation rates were significantly greater during Incr2 than Incr1 (p < 0.001). However, Δ (i.e., Incr2–Incr1) Fatmax, MFO, and fat oxidation rates were greater in the Heavy compared with the Light trial (p < 0.05). The fat oxidation kinetics during Incr2Heavy showed a greater dilatation and rightward asymmetry than Incr1Heavy, whereas only a greater dilatation was observed in Incr2Light (p < 0.05). This study showed that although to a lesser extent in the Light trial, both prior exercise sessions led to an increase in Fatmax, MFO, and absolute fat oxidation rates during Incr2, inducing significant changes in the shape of the fat oxidation kinetics.

Power Output During a Professional Men’s Road-Cycling Tour

Purpose:To quantify the power-output demands of men’s road-cycling stage racing using a direct measure of power output.Methods:Power-output data were collected from 207 races over 6 competition years on 31 Australian national male road cyclists. Subjects performed a maximal graded exercise test in the laboratory to determine maximum aerobic-power output, and bicycles were fitted with SRM power meters. Races were described as fl at, hilly, or criterium, and linear mixed modeling was used to compare the races.Results:Criterium was the shortest race and displayed the highest mean power output (criterium 262 ± 30 v hilly 203 ± 32 v fl at 188 ± 30 W), percentage total race time above 7.5 W/kg (crite-rium 15.5% ± 4.1% v hilly 3.8% ± 1.7% v fl at 3.5% ± 1.4%) and SD in power output (criterium 250 v hilly 165 v fl at 169 W). Approximately 67%, 80%, and 85% of total race time was spent below 5 W/kg for criterium, hilly and fl at races, respectively. About 70, 40, and 20 sprints above maximum aerobic-power output occurred during criterium, hilly, and fl at races, respectively, with most sprints being 6 to 10 s.Conclusions:These data extend previous research documenting the demands of men’s road cycling. Despite the relatively low mean power output, races were characterized by multiple high-intensity surges above maximum aerobic-power output. These data can be used to develop sport-specific interval-training programs that replicate the demands of competition.