The Improvement in Exercise Performance during Reduced Muscle Mass Exercise is Associated with an Increase in Femoral Blood Flow in Older and Younger Endurance-Trained Athletes.

This study investigated whether the improved performance observed with maximal self-paced single-leg (SL), compared with double-leg (DL) cycling, is associated with enhanced femoral blood flow and/or altered tissue oxygenation. The hyperaemic response to exercise was assessed in younger and older athletes. Power output was measured in 12 older (65 ± 4 y) and 12 younger (35 ± 5 y) endurance-trained individuals performing 2 x 3 min maximal self-paced exercise using SL and DL cycling. Blood flow (BF) in the femoral artery was assessed using Doppler ultrasound and muscle oxygenation was measured using near-infrared spectroscopy on the vastus lateralis. SL cycling elicited a greater power output (295 ± 83 vs 265 ± 70 W, P < 0.001) and peak femoral BF (1749.1 ± 533.3 vs 1329.7 ± 391.7 ml/min, P < 0.001) compared with DL cycling. Older individuals had a lower peak BF in response to exercise (1355.4 ± 385.8 vs 1765.2 ± 559.6 ml/min, P = 0.019) compared with younger individuals. Peak BF in response to exercise was correlated with power output during SL (r = 0.655, P = 0.002) and DL (r = 0.666, P = 0.001) cycling. The greater exercise performance during SL compared with DL cycling may be partly explained by a greater hyperaemic response when reducing active muscle mass. Despite regular endurance training, older athletes had a lower femoral BF in response to maximal self-paced exercise compared with younger athletes.

Single- Versus Double-Leg Cycling: Small Muscle Mass Exercise Improves Exercise Capacity to a Greater Extent in Older Compared With Younger Population.

Manipulating the amount of muscle mass engaged during exercise can noninvasively inform the contribution of central cardiovascular and peripheral vascular-oxidative functions to endurance performance. To better understand the factors contributing to exercise limitation in older and younger individuals, exercise performance was assessed during single-leg and double-leg cycling. 16 older (67 ± 5 years) and 14 younger (35 ± 5 years) individuals performed a maximal exercise using single-leg and double-leg cycling. The ratio of single-leg to double-leg cycling power (RatioPower SL/DL) was compared between age groups. The association between fitness (peak oxygen consumption, peak power output, and physical activity levels) and RatioPower SL/DL was explored. The RatioPower SL/DL was greater in older compared with younger individuals (1.14 ± 0.11 vs. 1.06 ± 0.08, p = .041). The RatioPower SL/DL was correlated with peak oxygen consumption (r = .886, p < .001), peak power output relative to body mass (r = .854, p < .001), and levels of physical activity (r = .728, p = .003) in the younger but not older subgroup. Reducing the amount of muscle mass engaged during exercise improved exercise capacity to a greater extent in older versus younger population and may reflect a greater reduction in central cardiovascular function compared with peripheral vascular-oxidative function with aging.

Breathing a low-density gas reduces respiratory muscle force development and marginally improves exercise performance in master athletes.

INTRODUCTION: We tested the hypothesis that breathing heliox, to attenuate the mechanical constraints accompanying the decline in pulmonary function with aging, improves exercise performance. METHODS: Fourteen endurance-trained older men (67.9 ± 5.9 year, [Formula: see text]O2max: 50.8 ± 5.8 ml/kg/min; 151% predicted) completed two cycling 5-km time trials while breathing room air (i.e., 21% O2-79% N2) or heliox (i.e., 21% O2-79% He). Maximal flow-volume curves (MFVC) were determined pre-exercise to characterize expiratory flow limitation (EFL, % tidal volume intersecting the MFVC). Respiratory muscle force development was indirectly determined as the product of the time integral of inspiratory and expiratory mouth pressure (∫Pmouth) and breathing frequency. Maximal inspiratory and expiratory pressure maneuvers were performed pre-exercise and post-exercise to estimate respiratory muscle fatigue. RESULTS: Exercise performance time improved (527.6 ± 38 vs. 531.3 ± 36.9 s; P = 0.017), and respiratory muscle force development decreased during inspiration (- 22.8 ± 11.6%, P < 0.001) and expiration (- 10.8 ± 11.4%, P = 0.003) with heliox compared with room air. EFL tended to be lower with heliox (22 ± 23 vs. 30 ± 23% tidal volume; P = 0.054). Minute ventilation normalized to CO2 production ([Formula: see text]E/[Formula: see text]CO2) increased with heliox (28.6 ± 2.7 vs. 25.1 ± 1.8; P < 0.001). A reduction in MIP and MEP was observed post-exercise vs. pre-exercise but was not different between conditions. CONCLUSIONS: Breathing heliox has a limited effect on performance during a 5-km time trial in master athletes despite a reduction in respiratory muscle force development.

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 (ß = 0.602; P < .001), maximal pedaling rate (ß = 0.309; P < .001), and relative maximal aerobic power output (ß = 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.

Effects of Carbohydrate, Caffeine, and Guarana on Cognitive Performance, Perceived Exertion, and Shooting Performance in High-Level Athletes.

Purpose: To investigate the effect of ingesting carbohydrate (CHO), caffeine  (CAF), and a guarana complex (GUAc) during a running exercise on cognitive performance, rating of perceived exertion (RPE), and shooting performance in high-level modern pentathlon athletes. Methods: A total of 10 athletes completed 4 counterbalanced sessions within a 2-wk period, corresponding to ingestions of CHO (30 g), GUAc (300 mg), CAF (200 mg), or placebo. The exercise involved a 40-min run on a treadmill at a steady speed, previously determined as a "somewhat hard" exercise (RPE 13). Shooting and cognitive performance (Simon task) were assessed in 3 phases: before exercise and ingestion, before exercise and after half ingestion, and after exercise and full ingestion. Drinks were consumed 40 min (250 mL) and 5 min (125 mL) prior to exercise and after 20 min of running (125 mL). RPE was assessed at 10-min intervals during exercise. Results: There was an interaction between drink and exercise on mean reaction time (P = .01, ηp2=.41 ) and a drink effect on RPE (P = .01, ηp2=.15 ). CHO, CAF, and GUAc enhanced the speed of information processing after exercise (P = .003, P = .004, and P = .04, respectively), but only CAF and GUAc decreased RPE (P = .002 and P = .02, respectively). Conclusion: The results highlight a beneficial effect of nutritional supplements on information processing and RPE. This finding is particularly interesting as decision-making processes are crucial in the performance of many sports.

Understanding the Physiological Requirements of the Mountain Bike Cross-Country Olympic Race Format.

Objectives: To evaluate the physiological requirements imposed by the current mountain biking Cross-Country Olympic (XCO) format. Methods: Sixteen Cross-Country cyclists competing at national or international level participated in this study. All participants completed a simulated and a real official race on a cycling-accredited race track. Oxygen consumption (O2) and heart rate (HR) values expressed as %O2max and %HRmax, respectively, were divided into three physiological intensity zones. The first zone (Z1) was the physiological region below VT1, the second zone (Z2) corresponded to a region between VT1 and VT2, and the third zone (Z3) was located between VT2 and VO2max. For power output, an additional fourth zone was considered above maximal aerobic power (MAP). Results: When competing in the current XCO format, 37.0 ± 17.9% of the race is performed above the second ventilatory threshold at a mean intensity of 87% O2max and 25% of the race was spent above MAP. This contribution varied between laps, with a very high intensity during the first lap and more aerobic subsequent laps. The durations of most of the periods beyond MAP oscillated between 5 and 30 s. Between these short, repeated bursts, low-intensity periods of exercise were recorded. Conclusion: The current XCO race format is an acyclical and intermittent exercise comparable to high-intensity team sports. Moreover, our results highlight the relevance of O2 values when analyzing XCO performance, they should be combined with commonly used HR and/or power output data.

The long and winding road: Effects of exercise intensity and type upon sustained attention.

Aerobic exercise enhances the ability to sustain attention (peaking at moderate intensities) by stimulating noradrenergic activity, which affects the fronto-parietal attention network. Prior exercise studies examining attention have focused on the influence of exercise intensity, yet few studies have examined the influence of the type of exercise protocol administered. Here, we propose that sustained attention is greater during (a) moderate compared to low intensity exercise, and (b) moderate intensity exercise administered at a varied-load compared to a constant-load but the same overall intensity. To test this hypothesis, we recorded attentional focus in twelve male cyclists during a sustained attention to response task (SART) in four conditions; at rest, and during exercise at a low constant-, moderate constant- and moderate varied-load intensity. The change in α-amylase (indicative of the noradrenergic response) from saliva samples and activation of the right prefrontal and parietal cortices using near-infrared spectroscopy were recorded. The findings revealed that moderate intensity exercise at a constant-load leads to faster responses and less accuracy in the SART than rest and low intensity exercise. Moderate intensity exercise at a variable-load leads to even faster responses but with no loss of accuracy in the SART. This pattern of results is explained by a larger increase in salivary α-amylase during moderate (constant and varied) intensity cycling and higher activation in the dorso-lateral prefrontal cortex during the varied, but not the constant-load condition. In conclusion, we show that, in addition to exercise intensity, the type of exercise also has important implications upon attentional focus. While moderate intensity exercise generally enhances attentional focus, monotonous exercise at a constant-load may mask such benefits.

Optimizing Heat Acclimation for Endurance Athletes: High- Versus Low-Intensity Training.

PURPOSE: To determine the effect of high- versus low-intensity training in the heat and ensuing taper period in the heat on endurance performance. METHODS: In total, 19 well-trained triathletes undertook 5 days of normal training and a 1-wk taper including either low- (heat acclimation [HA-L], n = 10) or high-intensity (HA-H, n = 9) training sessions in the heat (30°C, 50% relative humidity). A control group (n = 10) reproduced their usual training in thermoneutral conditions. Indoor 20-km cycling time trials (35°C, 50% relative humidity) were performed before (Pre) and after the main heat exposure (Mid) and after the taper (Post). RESULTS: Power output remained stable in the control group from Pre to Mid (effect size: -0.10 [0.26]) and increased from Mid to Post (0.18 [0.22]). The HA-L group demonstrated a progressive increase in performance from Pre to Mid (0.62 [0.33]) and from Mid to Post (0.53 [0.30]), alongside typical physiological signs of HA (reduced core temperature and heart rate and increased body-mass loss). While the HA-H group presented similar adaptations, increased perceived fatigue and decreased performance at Mid (-0.35 [0.26]) were evidenced and reversed at Post (0.50 [0.20]). No difference in power output was reported at Post between the HA-H and control groups. CONCLUSION: HA-H can quickly induce functional overreaching in nonacclimatized endurance athletes. As it was associated with a weak subsequent performance supercompensation, coaches and athletes should pay particular attention to training monitoring during a final preparation in the heat and reduce training intensity when early signs of functional overreaching are identified.

Short Trail Running Race: Beyond the Classic Model for Endurance Running Performance.

PURPOSE: This study aimed to examine the extent to which the classical physiological variables of endurance running performance (maximal oxygen uptake (V˙O2max), %V˙O2max at ventilatory threshold (VT), and running economy (RE)) but also muscle strength factors contribute to short trail running (TR) performance. METHODS: A homogeneous group of nine highly trained trail runners performed an official TR race (27 km) and laboratory-based sessions to determine V˙O2max, %V˙O2max at VT, level RE (RE0%) and RE on a +10% slope, maximal voluntary concentric and eccentric knee extension torques, local endurance assessed by a fatigue index (FI), and a time to exhaustion at 87.5% of the velocity associated with V˙O2max. A simple regression method and commonality analysis identifying unique and common coefficients of each independent variable were used to determine the best predictors for the TR race time (dependent variable). RESULTS: Pearson correlations showed that FI and V˙O2max had the highest correlations (r = 0.91 and r = -0.76, respectively) with TR performance. The other selected variables were not significantly correlated with TR performance. The analysis of unique and common coefficients of relative V˙O2max, %V˙O2max at VT, and RE0% provides a low prediction of TR performance (R = 0.48). However, adding FI and RE on a +10% slope (instead of RE0%) markedly improved the predictive power of the model (R = 0.98). FI and V˙O2max showed the highest unique (49.8% and 20.4% of total effect, respectively) and common (26.9% of total effect) contributions to the regression equation. CONCLUSIONS: The classic endurance running model does not allow for meaningful prediction of short TR performance. Incorporating more specific factors into TR such as local endurance and gradient-specific RE testing procedures should be considered to better characterize short TR performance.

Effects of High- Versus Moderate-Intensity Training on Neuroplasticity and Functional Recovery After Focal Ischemia.

BACKGROUND AND PURPOSE: This study was designed to compare the effects of high-intensity interval training (HIT) and moderate-intensity aerobic training (MOD) on functional recovery and cerebral plasticity during the first 2 weeks after cerebral ischemia. METHODS: Rats were randomized as follows: control (n=15), SHAM (n=9), middle cerebral artery occlusion (n=13), middle cerebral artery occlusion at day 1 (n=7), MOD (n=13), and HIT (n=13). Incremental tests were performed at day 1 (D1) and 14 (D14) to identify the running speed associated with the lactate threshold (SLT) and the maximal speed (Smax). Functional tests were performed at D1, D7, and D14. Microglia form, cytokines, p75NTR (pan-neurotrophin receptor p75), potassium-chloride cotransporter type 2, and sodium-potassium-chloride cotransporter type 1 expression were made at D15. RESULTS: HIT was more effective to improve the endurance performance than MOD and induced a fast recovery of the impaired forelimb grip force. The ionized calcium binding adaptor molecule 1 (Iba-1)-positive cells with amoeboid form and the pro- and anti-inflammatory cytokine expression were lower in HIT group, mainly in the ipsilesional hemisphere. A p75NTR overexpression is observed on the ipsilesional side together with a restored sodium-potassium-chloride cotransporter type 1/potassium-chloride cotransporter type 2 ratio on the contralesional side. CONCLUSIONS: Low-volume HIT based on lactate threshold seems to be more effective after cerebral ischemia than work-matched MOD to improve aerobic fitness and grip strength and might promote cerebral plasticity.

Cognitive Performance Enhancement Induced by Caffeine, Carbohydrate and Guarana Mouth Rinsing during Submaximal Exercise.

The aim of this study was to investigate the influence of serial mouth rinsing (MR) with nutritional supplements on cognitive performance (i.e., cognitive control and time perception) during a 40-min submaximal exercise. Twenty-four participants completed 4 counterbalanced experimental sessions, during which they performed MR with either placebo (PL), carbohydrate (CHO: 1.6 g/25 mL), guarana complex (GUAc: 0.4 g/25 mL) or caffeine (CAF: 67 mg/25 mL) before and twice during exercise. The present study provided some important new insights regarding the specific changes in cognitive performance induced by nutritional supplements. The main results were: (1) CHO, CAF and GUA MR likely led participants to improve temporal performance; (2) CAF MR likely improved cognitive control; and (3) CHO MR led to a likely decrease in subjective perception of effort at the end of the exercise compared to PL, GUA and CAF. Moreover, results have shown that performing 40-min submaximal exercise enhances information processing in terms of both speed and accuracy, improves temporal performance and does not alter cognitive control. The present study opens up new perspectives regarding the use of MR to optimize cognitive performance during physical exercise.

The differential effects of prolonged exercise upon executive function and cerebral oxygenation.

The acute-exercise effects upon cognitive functions are varied and dependent upon exercise duration and intensity, and the type of cognitive tasks assessed. The hypofrontality hypothesis assumes that prolonged exercise, at physiologically challenging intensities, is detrimental to executive functions due to cerebral perturbations (indicated by reduced prefrontal activity). The present study aimed to test this hypothesis by measuring oxygenation in prefrontal and motor regions using near-infrared spectroscopy during two executive tasks (flanker task and 2-back task) performed while cycling for 60min at a very low intensity and an intensity above the ventilatory threshold. Findings revealed that, compared to very low intensity, physiologically challenging exercise (i) shortened reaction time in the flanker task, (ii) impaired performance in the 2-back task, and (iii) initially increased oxygenation in prefrontal, but not motor regions, which then became stable in both regions over time. Therefore, during prolonged exercise, not only is the intensity of exercise assessed important, but also the nature of the cognitive processes involved in the task. In contrast to the hypofrontality hypothesis, no inverse pattern of oxygenation between prefrontal and motor regions was observed, and prefrontal oxygenation was maintained over time. The present results go against the hypofrontality hypothesis.

Compression Garments, Muscle Contractile Function, and Economy in Trail Runners.

BACKGROUND: Physiological mechanisms behind the use of compression garments (CGs) during off-road running are unknown. PURPOSE: To investigate the influence of wearing CGs vs conventional running clothing (CON) on muscle contractile function and running economy before and after short-distance trail running. METHODS: Knee-extensor neuromuscular function and running economy assessed from two 5-min treadmill runs (11 and 14 km/h) were evaluated before and after an 18.6-km short-distance trail run in 12 trained athletes wearing either CGs (stocking + short-tight) or CON. Quadriceps neuromuscular function was assessed from mechanical and EMG recording after maximal percutaneous electrical femoral-nerve stimulations (single-twitch doublets at 10 [Db10] and 100 Hz [Db100] delivered at rest and during maximal quadriceps voluntary contraction [MVC]). RESULTS: Running economy (in mL O2 · km-1 · kg-1) increased after trail running independent of the clothing condition and treadmill speeds (P < .001). Similarly, MVC decreased after CON and CGs conditions (-11% and -13%, respectively, P < .001). For both clothing conditions, a significant decrease in quadriceps voluntary activation, Db10, Db100, and the low-to-high frequency doublet ratio were observed after trail running (time effect, all P < .01), without any changes in rectus femoris maximal M-wave. CONCLUSIONS: Wearing CGs does not reduce physiological alterations induced during short-distance trail running. Further studies should determine whether higher intensity of compression pressure during exercises of longer duration may be effective to induce any physiological benefits in experienced trail runners.

Saving mental effort to maintain physical effort: a shift of activity within the prefrontal cortex in anticipation of prolonged exercise.

Executive functioning and attention require mental effort. In line with the resource conservation principle, we hypothesized that mental effort would be saved when individuals expected to exercise for a long period. Twenty-two study participants exercised twice on a cycle ergometer for 10 min at 60% of their maximal aerobic power, with the expectation of exercising for either 10 min or 60 min. Changes in activity in the right dorsolateral prefrontal cortex (rdlPFC) and right medial frontal cortex (rmPFC) were investigated by measuring oxyhemoglobin using near-infrared spectroscopy. Attentional focus and ratings of perceived exertion were assessed at three time points (200, 400, and 600 s). The oxyhemoglobin concentration was lower in the rdlPFC and higher in the rmPFC under the 60-min than under the 10-min condition. Also, attention was less focused in the 60-min than in the 10-min condition. We discuss these results as possible evidence of a disengagement of the brain regions associated with mental effort (executive network), in favor of brain regions linked to resting activity (the default network), in order to save mental resources for the maintenance of exercise.

Periodization of Carbohydrate Intake: Short-Term Effect on Performance.

BACKGROUND: "Sleep-low" consists of a sequential periodization of carbohydrate (CHO) availability-low glycogen recovery after "train high" glycogen-depleting interval training, followed by an overnight-fast and light intensity training ("train low") the following day. This strategy leads to an upregulation of several exercise-responsive signaling proteins, but the chronic effect on performance has received less attention. We investigated the effects of short-term exposure to this strategy on endurance performance. METHODS: Following training familiarization, 11 trained cyclists were divided into two groups for a one-week intervention-one group implemented three cycles of periodized CHO intake to achieve the sleep-low strategy over six training sessions (SL, CHO intake: 6 g·kg-1·day-1), whereas the control group consumed an even distribution of CHO over the day (CON). Tests were a 2 h submaximal ride and a 20 km time trial. RESULTS: SL improved their performance (mean: +3.2%; p < 0.05) compared to CON. The improvement was associated with a change in pacing strategy with higher power output during the second part of the test. No change in substrate utilization was observed after the training period for either group. CONCLUSION: Implementing the "sleep-low" strategy for one week improved performance by the same magnitude previously seen in a three-week intervention, without any significant changes in selected markers of metabolism.

The impact of sleeping with reduced glycogen stores on immunity and sleep in triathletes.

PURPOSE: We investigated the effects of a 3-week dietary periodization on immunity and sleep in triathletes. METHODS: 21 triathletes were divided into two groups with different nutritional guidelines during a 3-week endurance training program including nine twice a day sessions with lowered (SL group) or maintained (CON group) glycogen availability during the overnight recovery period. In addition to performance tests, sleep was monitored every night. Systemic and mucosal immune parameters as well as the incidence of URTI were monitored every week of the training/nutrition protocol. Two-ways ANOVA and effect sizes were used to examine differences in dependent variables between groups at each time point. RESULTS: The SL group significantly improved 10 km running performance (-1 min 13 s, P < 0.01, d = 0.38), whereas no improvement was recorded in the CON group (-2 s, NS). No significant changes in white blood cells counts, plasma cortisol and IL-6 were recorded over the protocol in both groups. The vitamin D status decreased in similar proportions between groups, whereas salivary IgA decreased in the SL group only (P < 0.05, d = 0.23). The incidence of URTI was not altered in both groups. All participants in both groups went to bed earlier during the training program (SL -20 min, CON -27 min, P < 0.05, d = 0.28). In the SL group, only sleep efficiency slightly decreased by 1.1 % (P < 0.05, d = 0.25) and the fragmentation index tended to increase at the end of the protocol (P = 0.06). CONCLUSION: Sleeping and training the next morning regularly with reduced glycogen availability has minimal effects on selected markers of immunity, the incidence of URTI and sleeping patterns in trained athletes.

Sprint Acceleration Mechanics in Masters Athletes.

PURPOSE: The best sprint performances are usually reached between the ages of 20 and 30 yr; however, even in well-trained individuals, performance continues to decrease with age. Although this inevitable decrease in performance has been related to reductions in muscular force, velocity, and power capabilities, these measures have not been assessed in the specific context of sprinting. The aim of this study was to investigate the mechanical outputs of sprinting acceleration among masters sprinters to better understand the mechanical underpinnings of the age-related decrease in sprint performance. METHODS: The study took place during an international masters competition, with testing performed at the end of the warm-up for official sprint races. Horizontal ground reaction force, velocity, mechanical power outputs, and mechanical effectiveness of force application were estimated from running velocity-time data during a 30-m sprint acceleration in 27 male sprinters (39-96 yr). Data were presented in the form of age-related changes and compared with elite young sprinters data. RESULTS: Maximal force, velocity, and power outputs decreased linearly with age (all r > 0.84, P < 0.001), at a rate of ~1% per year. Maximal power of the oldest subject tested was approximately one-ninth of that of younger world-class sprinters (3.57 vs 32.1 W·kg). Although the maximal effectiveness of horizontal force application also decreased with age, its decrease with increasing velocity within the sprint acceleration was not age dependent. CONCLUSIONS: In addition to lower neuromuscular force, velocity, and power outputs, masters sprinters had a comparatively lower effectiveness of force application, especially at the beginning of the sprint.

Effects of Footwear and Fatigue on Running Economy and Biomechanics in Trail Runners.

PURPOSE: This study aimed to examine the effects of footwear and neuromuscular fatigue induced by short distance trail running (TR) on running economy (RE) and biomechanics in well-trained and traditionally shod runners. METHODS: RE, vertical and leg stiffness (Kvert and Kleg), as well as foot strike angle were measured from two 5-min treadmill running stages performed at a speed of 2.5 (with 10% grade, uphill running) and 2.77 m·s (level running) before and after an 18.4-km TR exercise (approximately 90% of maximal heart rate) in runners wearing minimalist shoes (MS), MS plus added mass (MSm), or traditional shoes (TS). Maximal voluntary contraction torque of knee extensors and perceived muscle pain were also evaluated before and after TR. RESULTS: Maximal voluntary contraction values decreased after TR in all footwear conditions (P < 0.001), indicating the occurrence of neuromuscular fatigue. In the nonfatigued condition, runners exhibited a better RE only during level running in MS and MSm (i.e., combined effects of shoe mass and midsole geometry), in association with significant decreases in foot strike angle (P < 0.05). However, no significant difference in RE was observed between shod conditions after TR during either uphill or level running. Decreases in both Kvert/Kleg and foot strike angle were more pronounced during running in MS and MSm (P < 0.05) compared with TS, whatever the period. Calf pain increased after TR when wearing MS and MSm compared with TS (P < 0.05). CONCLUSIONS: These findings indicated specific alterations in RE and biomechanics over time during the MS and MSm conditions compared with the TS condition. Future studies are warranted to evaluate the relationship between RE and footwear with fatigue in experienced minimally shod runners.

Running Energy Cost and Spring-Mass Behavior in Young versus Older Trained Athletes.

PURPOSE: The aim of this study was to compare energy cost of running and lower limb spring-mass characteristics and maximal power between young and older highly trained runners. METHODS: Twenty highly trained male endurance runners were divided into two groups: young and master athletes. Two testing sessions were used to measure and compare (i) lower limb power during three jumping tests (squat jump (SJ), countermovement jump (CMJ), and rebound jump (RJ)) as well as stiffness during the RJ test and running trials (using an OptoJump system (Microgate, Bolzano, Italy) placed on the floor for jumping and on each side of the treadmill belt for running), and (ii) the energy cost of running and oxygen consumption (V˙O2) kinetics (using an Oxycon Pro breath-by-breath gas analyzer (Jaeger, Höchberg, Germany)) at three speeds: 10 km·h, self-selected speed, and speed corresponding to 90% of the second ventilatory threshold (VT2). RESULTS: Energy cost of running was higher in masters than in young athletes at all speeds (10 km·h, 13.0%; self-selected, 10.8%; 90% VT2, 7.7% on average). Jumping power was lower in masters (SJ, -28.0%; CMJ, -30.5%; RJ, -27.9%) and significantly correlated with energy cost at 10 km·h and at self-selected speed (10 km·h: r = -0.71, -0.70, -0.47; self-selected speed: r = -0.76, -0.74, -0.58, respectively). RJ stiffness was also lower in masters (-27.8%), although stiffness during running showed no difference between groups. CONCLUSIONS: A long-lasting running practice seemed to preserve the bouncing mechanism of master athletes, yet their energy cost was higher when compared with younger runners, which might have been associated with a lower muscle power.