Analysis of elite road-cycling sprints in relation to maximal power-velocity-endurance profile: a longitudinal one-case study.

The aims of the present study were to characterize the mechanical output of final road sprints of an elite sprinter during international competitions in relation to his power-velocity-endurance characteristics and to investigate the relationship between this sprint performance and the power produced during preceding phases of the race. The sprinter performed a set of short and long sprints (5 to 15-s) on a cycle ergometer to determine his maximal power-velocity-endurance profile. Based on eleven races, the distribution of power throughout each race, peak and mean power (Ppeak and Pmean ) and associated pedaling rates (vPpeak and vPmean ) during the final sprint were analyzed. The power-velocity-endurance profile of the sprinter indicated that his theoeretical mean maximal power and corresponding optimal pedaling rate ranged from 20.0 W.kg-1 (124 rpm) for a 1-s sprint to 15.0 W.kg-1 (109 rpm) for 20 s. Race data showed that final road sprints were mainly performed on the ascending limb of the power-velocity relationship (vPpeak , 104 ± 8 and vPmean , 101 ± 8 rpm). Additionally, Ppeak and Pmean were lower than the theoretical maximal power determined from the power-velocity-endurance profile (9.9 ± 7.0% and 10.6 ± 9.8%, respectively), which highlighted a significant state of fatigue induced by the race. Finally, sprint power exhibited a high variability between races and was strongly related to the level of power produced during the last minute before the sprint. These findings show the importance of considering both the power-velocity-endurance qualities and the power demand of the last lead-up phase before the sprint in order to optimize final sprint performance.

Positive Effects of Pre-exercise Metabolic Alkalosis on Perceived Exertion and Post-exercise Squat Jump Performance in World-Class Cyclists.

ABSTRACT: Thomas, C, Delfour-Peyrethon, R, Dorel, S, and Hanon, C. Positive effects of pre-exercise metabolic alkalosis on perceived exertion and post-exercise squat jump performance in world-class cyclists. J Strength Cond Res 36(9): 2602-2609, 2022-This study aimed to determine the effects of pre-exercise alkalosis in world-class cyclists on their general (rate of perceived exertion [RPE]) and local (category-ratio scale [CR10]) perceived rates of exertion and acid-base status during 2 types of training sessions. Eight world-class cyclists ingested either sodium bicarbonate (BIC) or a placebo (PLA) in a double-blind and randomized order before performing 4 × 1,000 m constant-power sprints (CP) or 3 × 500 m all-out sprints (AO), with 20 minutes of recovery time between each session. For AO, the performance was assessed through the cycling sprint velocity and a squat jump test during recovery. During both tests, RPE, CR10, and acid-base status were measured. Sodium bicarbonate ingestion was effective in inducing pre-exercise alkalosis, compared with a PLA ( p < 0.05). During CP, performance and RPE were the same for BIC and PLA ( p > 0.05) with no time effect. The CR10 increased for the last sprint in PLA ( p < 0.05) but was attenuated in BIC (BIC: 6 vs. PLA: 8.2; p < 0.05), whereas there was no difference in acid-base status. During AO, RPE and CR10 increased with time, with no BIC effect, whereas blood lactate concentration was different ( p < 0.05). Sodium bicarbonate supplementation had no effect on overall repeated sprints ( p > 0.05). However, world-class athletes responded to BIC with higher squat jump performance than the PLA condition after AO ( p < 0.05). Our results suggest a positive influence of pre-exercise alkalosis in world-class cyclists on local perception of efforts after constant load sprints and an attenuation of muscle power output decline postsprint, as evidenced by improved squat jump performance after all-out cycling effort.

Validity and Reliability of the Stages Cycling Power Meter.

Granier, C, Hausswirth, C, Dorel, S, and Le Meur, Y. Validity and reliability of the stages cycling power meter. J Strength Cond Res 34(12): 3554-3559, 2020-This study aimed to determine the validity and the reliability of the Stages power meter crank system (Boulder, United States) during several laboratory cycling tasks. Eleven trained subjects completed laboratory cycling trials on an indoor cycle fitted with SRM Professional and Stages systems. The trials consisted of an incremental test at 100 W, 200 W, 300 W, 400 W, and four 7-s sprints. The level of pedaling asymmetry was determined for each cycling intensity during a similar protocol completed on a Lode Excalibur Sport ergometer. The reliability of Stages and SRM power meters was compared by repeating the incremental test during a test-retest protocol on a Cyclus 2 ergometer. Over power ranges of 100-1,250 W, the Stages system produced trivial to small differences compared with the SRM (standardized typical error values of 0.06, 0.24, and 0.08 for the incremental, sprint, and combined trials, respectively). A large correlation was reported between the difference in power output (PO) between the 2 systems and the level of pedaling asymmetry (r = 0.58, p < 0.001). Recalculating PO of the Stages system according to the level of pedaling asymmetry provided only marginal improvements in PO measures. The reliability of the Stages power meter at the submaximal intensities was similar to the SRM Professional model (coefficient of variation: 2.1 and 1.3% for Stages and SRM, respectively). The Stages system is a suitable device for PO measurements, except when a typical error of measurement <3.0% over power ranges of 100-1,250 W is expected.

Do individual differences in the distribution of activation between synergist muscles reflect individual strategies?

Individual differences in the distribution of activation between synergist muscles have been reported during a wide variety of tasks. Whether these differences represent actual individual strategies is unknown. The aims of this study were to: (i) test the between-day reliability of the distribution of activation between synergist muscles, (ii) to determine the robustness of these strategies between tasks, and to (iii) describe the inter-individual variability of activation strategies in a large sample size. Eighty-five volunteers performed a series of single-joint isometric tasks with their dominant leg [knee extension and plantarflexion at 25% of maximal voluntary contraction (MVC)] and locomotor tasks (pedalling and walking). Of these participants, 62 performed a second experimental session that included the isometric tasks. Myoelectrical activity of six lower limb muscles (the three superficial heads of the quadriceps and the three heads of the triceps surae) was measured using surface electromyography (EMG) and normalized to that measured during MVC. When considering isometric contractions, distribution of normalized EMG amplitude among synergist muscles, considered here as activation strategies, was highly variable between individuals (15.8% < CV < 42.7%) and robust across days (0.57 < ICC < 0.82). In addition, individual strategies observed during simple single-joint tasks were correlated with those observed during locomotor tasks [0.37 < r < 0.76 for quadriceps (n = 83); 0.30 < r < 0.66 for triceps surae (n = 82); all P < 0.001]. Our results provide evidence that people who bias their activation to a particular muscle do so during multiple tasks. Even though inter-individual variability of EMG signals has been well described, it is often considered noise which complicates the interpretation of data. This study provides evidence that variability results from actual differences in activation strategies.

Is reaction time altered by mental or physical exertion?

PURPOSE: Reaction time, classically divided into premotor time and electromechanical delay (EMD), can be determinant in daily life or sport situations. While some previous studies reported a negative impact of both muscle and mental fatigue on reaction time, the respective contributions of premotor time and EMD to the changes of reaction time remains unclear. The aim of the study was, therefore, to assess the effects of both muscle and mental effort on reaction time and its components. METHODS: Thirteen subjects performed three conditions (mental effort condition, i.e., 14 min of a mathematical cognitive task; muscle effort condition, i.e., intermittent contractions of the biceps brachii; control condition, i.e., watching a documentary). Before and after each condition, reaction time, premotor time and EMD were measured during voluntary contractions of the biceps brachii. EMD was also measured during evoked contractions of the biceps brachii to separate the parts due to the onset of muscle fascicle motion and the onset of force production. RESULTS: Reaction time and premotor time remained stable regardless of the condition considered (all P values > 0.05). EMD increased only after the muscle effort condition (+ 25% during voluntary contractions, no significant; + 17% during evoked contractions, P = 0.001), mainly due to an increase in the passive part of the series elastic component. CONCLUSION: Our study showed that neither mental nor muscle effort has a negative effect on simple reaction time during voluntary contractions.

The slack test does not assess maximal shortening velocity of muscle fascicles in humans.

The application of a series of extremely high accelerative motor-driven quick releases while muscles contract isometrically (i.e. slack test) has been proposed to assess unloaded velocity in human muscle. This study aimed to measure gastrocnemius medialis fascicle shortening velocity (VF) and tendinous tissue shortening velocity during motor-driven quick releases performed at various activation levels to assess the applicability of the slack test in humans. Gastrocnemius medialis peak VF and joint velocity recorded from 25 participants using high frame rate ultrasound during quick releases (at activation levels from 0% to 60% of maximal voluntary isometric torque) and during fast contractions without external load (ballistic condition) were compared. Unloaded joint velocity calculated using the slack test method increased whereas VF decreased with muscle activation level (P≤0.03). Passive and low-level quick releases elicited higher VF values (≥41.8±10.7 cm s-1) compared with the ballistic condition (36.3±8.7 cm s-1), while quick releases applied at 60% of maximal voluntary isometric torque produced the lowest VF These findings suggest that initial fascicle length, complex fascicle-tendon interactions, unloading reflex and motor-driven movement pattern strongly influence and limit the shortening velocity achieved during the slack test. Furthermore, VF elicited by quick releases is likely to reflect substantial contributions of passive processes. Therefore, the slack test is not appropriate to assess maximal muscle shortening velocity in vivo.

Mental fatigue alters the speed and the accuracy of the ball in table tennis.

This study aimed at evaluating the effects of mental and muscle fatigue on table tennis performance. Mental fatigue (MF) was induced by completion of 90 minutes of the AX-CPT; muscle fatigue was induced by completion of an eccentric exercise performed with the elbow flexors (biceps fatigue, BF) or the knee extensors (quadriceps fatigue, QF). The control condition consisted of watching a movie. Stroke parameters (speed and accuracy of the ball), as well as feelings of fatigue and force production capacity of the elbow flexors (BF, MF and control conditions) and knee extensors (QF condition), were assessed pre and post fatigue protocols. Feelings of fatigue increased post fatigue protocols. Force production capacity decreased only in the BF and QF conditions. BF and MF induced a decrease in accuracy. This decrease in accuracy was associated with an increased ball speed in the BF condition, and a decreased ball speed in the MF condition. QF had a negligible effect on stroke performance. Our results suggest that both mental fatigue, and muscle fatigue, significantly impair table tennis performance and therefore coaches should take into account both the physical and mental state of table tennis players to optimize performance.

Motor adaptations to local muscle pain during a bilateral cyclic task.

The aim of this study was to determine how unilateral pain, induced in two knee extensor muscles, affects muscle coordination during a bilateral pedaling task. Fifteen participants performed a 4-min pedaling task at 130 W in two conditions (Baseline and Pain). Pain was induced by injection of hypertonic saline into the vastus medialis (VM) and vastus lateralis (VL) muscles of one leg. Force applied throughout the pedaling cycle was measured using an instrumented pedal and used to calculate pedal power. Surface electromyography (EMG) was recorded bilaterally from eight muscles to assess changes in muscle activation strategies. Compared to Baseline, during the Pain condition, EMG amplitude of muscles of the painful leg (VL and VM-the painful muscles, and RF-another quadriceps muscle with no pain) was lower during the extension phase [(mean ± SD): VL: -22.5 ± 18.9%; P < 0.001; VM: -28.8 ± 19.9%; P < 0.001, RF: -20.2 ± 13.9%; P < 0.001]. Consistent with this, pedal power applied by the painful leg was also lower during the extension phase (-16.8 ± 14.2 W, P = 0.001) during Pain compared to Baseline. This decrease was compensated for by an 11.3 ± 8.1 W increase in pedal power applied by the non-painful leg during its extension phase (P = 0.04). These results support pain adaptation theories, which suggest that when there is a clear opportunity to compensate, motor adaptations to pain occur to decrease load within the painful tissue. Although the pedaling task offered numerous possibilities for compensation, only between-leg compensations were systematically observed. This finding is discussed in relation to the mechanical and neural constraints of the pedaling task.

Muscle fascicle shortening behaviour of vastus lateralis during a maximal force-velocity test.

PURPOSE: Muscle fascicles-tendon interactions are the main determinant in production of high joint velocity. Currently, no study has investigated the muscle fascicles behaviour of knee extensor muscles until the highest reachable velocity (e.g., unloaded knee extension). We aimed to track the changes in vastus lateralis fascicles length during knee extensions to quantify muscle fascicles and tendinous tissues contributions to muscle-tendon unit shortening and to determine maximal muscle fascicles shortening velocity. METHODS: Fifteen participants performed isokinetic and isoinertial knee extensions, and ultrafast ultrasound imaging was used to observe the vastus lateralis fascicles from low to very high joint velocity. RESULTS: The muscle fascicles shortening velocity increased linearly with the increase in knee joint velocity up to the maximal joint velocity (mean R 2 = 0.93 ± 0.08). Muscle fascicles contribution to muscle-tendon unit shortening velocity was almost constant regardless of the condition (83 ± 23%). Using Hill's equation, the maximal velocity of knee joint and muscle fascicles was determined at 1000 ± 489°s-1 and 5.1 ± 2.0 L0 s-1 (47.4 ± 18.7 cm s-1), respectively. CONCLUSIONS: Contribution of muscle fascicles to the muscle-tendon unit shortening velocity was much higher for the vastus lateralis in this study compared to the gastrocnemius medialis in two previous studies. Moreover, this contribution of muscle fascicles shortening velocity was constant whatever the velocity condition, even at the highest reachable velocity. Thus, the vastus lateralis fascicles shortening velocity increases linearly with the knee joint velocity until high velocities and its behaviour strongly accorded with the classical Hill's force-velocity relationship.

Effects of pre-exercise alkalosis on the decrease in VO2 at the end of all-out exercise.

PURPOSE: This study determined the effects of pre-exercise sodium bicarbonate ingestion (ALK) on changes in oxygen uptake (VO2) at the end of a supramaximal exercise test (SXT). METHODS: Eleven well-trained cyclists completed a 70-s all-out cycling effort, in double-blind trials, after oral ingestion of either 0.3 g kg(-1) of sodium bicarbonate (NaHCO3) or 0.2 g kg(-1) body mass of calcium carbonate (PLA). Blood samples were taken to assess changes in acid-base balance before the start of the supramaximal exercise, and 0, 5 and 8 min after the exercise; ventilatory parameters were also measured at rest and during the SXT. RESULTS: At the end of the PLA trial, which induced mild acidosis (blood pH = 7.20), subjects presented a significant decrease in VO2 (P < 0.05), which was related to the amplitude of the decrease in minute ventilation (VE) during the SXT (r = 0.70, P < 0.01, n = 11). Pre-exercise metabolic alkalosis significantly prevented the exercise-induced decrease in VO2 in eleven well-trained participants (PLA:12.5 ± 2.1 % and ALK: 4.9 ± 0.9 %, P < 0.05) and the decrease in mean power output was significantly less pronounced in ALK (P < 0.05). Changes in the VO2 decrease between PLA and ALK trials were positively related to changes in the VE decrease (r = 0.74, P < 0.001), but not to changes in power output (P > 0.05). CONCLUSIONS: Pre-exercise alkalosis counteracted the VO2 decrease related to mild acidosis, potentially as a result of changes in VE and in muscle acid-base status during the all-out supramaximal exercise.

Muscle and tendon stiffness assessment using the alpha method and ultrafast ultrasound.

PURPOSE: The alpha method enables the dissociation of the passive (i.e., tendinous tissues) and active (i.e., fascicles) part of muscle-tendon stiffness. It is based on two main assumptions (i.e., a constant tendon stiffness and a muscle stiffness proportional to the torque produced), which have not been approved in vivo. The purpose of this study was to validate these two assumptions using ultrafast ultrasound, and to compare fascicle and tendon stiffness as determined by both methods. METHODS: Ten healthy males performed a fast-stretch experiment on the ankle plantar flexors. The mathematical model of the alpha method allowed to estimate the stiffness of muscle and tendinous tissues on the basis of the assumptions associated to the behaviors of muscle fascicles and tendinous tissues. Muscle and tendon stiffness of the gastrocnemius medialis were also calculated from ultrafast ultrasound measurements. RESULTS: Muscle stiffness measured by the ultrasound method increased from 217 ± 83 to 720 ± 265 N/mm with an increasing level of force (from 30 to 90 % MVC). Tendinous stiffness measured by the ultrasound method remained constant across the force level (P < 0.001). However, the stiffness values obtained with both methods were significantly different (P < 0.001). CONCLUSIONS: In conclusion, these findings validate the two main assumptions underlying the alpha method using ultrasound. Differences in stiffness values obtained with alpha and ultrasound methods could be associated with physiological and geometrical differences between the whole plantar flexors muscles characterized by the alpha method and the gastrocnemius medialis assessed with the ultrasound method.

Muscle-Tendon Unit Length Measurement Using 3D Ultrasound in Passive Conditions: OpenSim Validation and Development of Personalized Models.

This study investigated the validity of using OpenSim to measure muscle-tendon unit (MTU) length of the bi-articular lower limb muscles in several postures (shortened, lengthened, a combination of shortened and lengthened involving both joints, neutral and standing) using 3D freehand ultrasound (US), and to propose new personalized models. MTU length was measured on 14 participants and 6 bi-articular muscles (semimembranosus SM, semitendinosus ST, biceps femoris BF, rectus femoris RF, gastrocnemius medialis GM and gastrocnemius lateralis GL), considering 5 to 6 postures. MTU length was computed using OpenSim with three different models: OS (the generic OpenSim scaled model), OS + INSER (OS with personalized 3D US MTU insertions), OS + INSER + PATH (OS with personalized 3D US MTU insertions and path obtained from one posture). Significant differences in MTU length were found between OS and 3D US models for RF, GM and GL (from - 6.3 to 10.9%). Non-significant effects were reported for the hamstrings, notably for the ST (- 1.5%) and BF (- 1.9%), while the SM just crossed the alpha level (- 3.4%, p = 0.049). The OS + INSER model reduced the magnitude of bias by an average of 4% for RF, GM and GL. The OS + INSER + PATH model showed the smallest biases in length estimates, which made them negligible and non-significant for all the MTU (i.e. ≤ 2.2%). A 3D US pipeline was developed and validated to estimate the MTU length from a limited number of measurements. This opens up new perspectives for personalizing musculoskeletal models using low-cost user-friendly devices.

Bicycle Set-Up Dimensions and Cycling Kinematics: A Consensus Statement Using Delphi Methodology.

Bicycle set-up dimensions and cycling kinematic data are important components of bicycle fitting and cyclist testing protocols. However, there are no guidelines on how bicycles should be measured and how kinematic data should be collected to increase the reliability of outcomes. This article proposes a consensus regarding bicycle set-up dimensions and recommendations for collecting cycling-related kinematic data. Four core members recruited panellists, prepared the document to review in each round for panellists, analysed the scores and comments of the expert panellists, reported the decisions and communicated with panellists. Fourteen experts with experience in research involving cycling kinematics and/or bicycle fitting agreed to participate as panellists. An initial list of 17 statements was proposed, rated using a five-point Likert scale and commented on by panellists in three rounds of anonymous surveys following a Delphi procedure. The consensus was agreed upon when more than 80% of the panellists scored the statement with values of 4 and 5 (moderately and strongly agree) with an interquartile range of less than or equal to 1. A consensus was achieved for eight statements addressing bicycle set-up dimensions (e.g. saddle height, saddle setback, etc.) and nine statements for cycling kinematic assessment (e.g. kinematic method, two-dimensional methodology, etc.). This consensus statement provides a list of recommendations about how bicycle set-up dimensions should be measured and the best practices for collecting cycling kinematic data. These recommendations should improve the transparency, reproducibility, standardisation and interpretation of bicycle measurements and cycling kinematic data for researchers, bicycle fitters and cycling related practitioners.

Strength capacity of lower-limb muscles in world-class cyclists: new insights into the limits of sprint cycling performance.

This study aimed to determine the relationship between the torque-generating capacity in sprint cycling and the strength capacity of the six lower-limb muscle groups in male and female world-class sprint cyclists. Eleven female and fifteen male top-elite cyclists performed 5-s sprints at maximal power in seated and standing positions. They also performed a set of maximal voluntary ankle, knee and hip flexions and extensions to assess single-joint isometric and isokinetic torques. Isokinetic torques presented stronger correlations with cycling torque than isometric torques for both body positions, regardless of the group. In the female group, knee extension and hip flexion torques accounted for 81.2% of the variance in cycling torque, while the ability to predict cycling torque was less evident in males (i.e., 59% of variance explained by the plantarflexion torque only). The standing condition showed higher correlations than seated and a better predictive model in males (R2 = 0.88). In addition to the knee extensors and flexors and hip extensors, main power producers, the strength capacity of lower-limb distal plantarflexor (and to a lesser extent dorsiflexor) muscles, as well as other non-measured qualities (e.g., the upper body), might be determinants to produce such extremely high cycling torque in males.

Physiological demand and pacing strategy during the new combined event in elite pentathletes.

To evaluate the physiological demands and effects of different pacing strategies on performance during the new combined event (CE) of the modern pentathlon (consisting of three pistol shooting sessions interspersed by three 1-km running legs). Nine elite pentathletes realised five tests: a free-paced CE during an international competition; an incremental running test to determine [Formula: see text] and its related velocity ([Formula: see text]) and three experimental time-trial CE, where the pacing strategy was manipulated (CE(ref), CE(100%), CE(105%)). CE(ref) reproduced the international competition strategy with a 170-m fast running start within the first 2 km. CE(100%) and CE(105%) imposed a constant strategy over km-1 and km-2 with a velocity of 100 and 105% of the mean speed adopted over the same sections during the international competition, respectively. Km-3 was always self-paced. The subjects ran CE(ref) at 99 ± 4% of [Formula: see text] and reached 100 ± 5, 100 ± 7, 99 ± 8% of [Formula: see text] at the end of kilometres 1, 2 and 3, respectively ([Formula: see text]: 72 ± 6 mL O(2) min(-1) kg(-1)), with a peak blood lactate concentration of 13.6 ± 1.5 mmol L(-1). No significant differences in overall performance were found between the pacing conditions (753 ± 30, 770 ± 39, 768 ± 27 s for CE(ref), CE(100%) and CE(105%), respectively, p = 0.63), but all of the shooting performance parameters were only stable in CE(ref). Completion of CE by elite pentathletes elicits a maximal aerobic contribution coupled with a high glycolytic supply. Manipulating the mean running speed over km-1 and km-2 had strong influence on the overall pacing strategy and induced minor differences in shooting performance, but it did not affect overall performance.

Consistency of muscle synergies during pedaling across different mechanical constraints.

The purpose of the present study was to determine whether muscle synergies are constrained by changes in the mechanics of pedaling. The decomposition algorithm used to identify muscle synergies was based on two components: "muscle synergy vectors," which represent the relative weighting of each muscle within each synergy, and "synergy activation coefficients," which represent the relative contribution of muscle synergy to the overall muscle activity pattern. We hypothesized that muscle synergy vectors would remain fixed but that synergy activation coefficients could vary, resulting in observed variations in individual electromyographic (EMG) patterns. Eleven cyclists were tested during a submaximal pedaling exercise and five all-out sprints. The effects of torque, maximal torque-velocity combination, and posture were studied. First, muscle synergies were extracted from each pedaling exercise independently using non-negative matrix factorization. Then, to cross-validate the results, muscle synergies were extracted from the entire data pooled across all conditions, and muscle synergy vectors extracted from the submaximal exercise were used to reconstruct EMG patterns of the five all-out sprints. Whatever the mechanical constraints, three muscle synergies accounted for the majority of variability [mean variance accounted for (VAF) = 93.3 ± 1.6%, VAF (muscle) > 82.5%] in the EMG signals of 11 lower limb muscles. In addition, there was a robust consistency in the muscle synergy vectors. This high similarity in the composition of the three extracted synergies was accompanied by slight adaptations in their activation coefficients in response to extreme changes in torque and posture. Thus, our results support the hypothesis that these muscle synergies reflect a neural control strategy, with only a few timing adjustments in their activation regarding the mechanical constraints.

Muscle-tendon unit length changes in knee extensors and flexors during alpine skiing.

This study characterised the thigh muscle-tendon unit length variations (MTUv) in elite alpine skiing. MTUv were modelled for seven muscles from knee and hip angles in 17 national team skiers during 1602 cycles (546 Slalom (SL), 908 Giant-Slalom (GS), 136 Super-Giant (SG) and 12 Downhill (DH) cycles). The biarticular rectus femoris showed a dynamic pattern on both legs, especially in SL. On the other side, vastii displayed a stable length on the inside leg in all disciplines (37-46% of the cycle), contrasting with their dynamic behaviour on the outside leg being quasi-static for only 3% (SL) to 27% (DH) of the cycle. SL showed the largest amplitude of MTUv followed by GS, SG and DH. For vastus lateralis, MTUv was ~60%Lr.s-1 in SL but only ~12%Lr.s-1 in DH. In SL, a fine desynchronisation between both joints led to nearly constant MTUv (slow lengthening lasting ~45-51% of the cycle) for the biarticular hamstrings separated by faster variations during turn switch from outside to inside leg. In summary, biarticular MTUv were not characterised by single-joint behaviours, suggesting that extrapolating contraction regimen from knee joint only is not accurate in alpine skiing.

Performance factors in the new combined event of modern pentathlon.

The aims of this study were to determine (1) the individual tactics employed by elite modern pentathletes within each discipline of the new combined running-shooting event, and (2) the consequences of these strategies on overall performance. For 36 male pentathletes competing in a World Cup event, we measured running velocity, transition time, shooting time, shooting accuracy, and delay per shot. Performances of the top third of athletes, middle third of athletes, and the bottom third of athletes in the combined event were compared. The difference in overall performance between the top third and middle/bottom thirds was predominately associated with better shooting accuracy (79 +/- 13%, 68 +/- 12%, and 64 +/- 10% success rate for top, middle, and bottom third, respectively) and faster shooting time (86 +/- 16 s, 109 +/- 19 s, and 117 +/- 23 s for top, middle, and bottom third, respectively). No significant differences in running velocity, transition time or delay per shot were observed among the three groups. All the competitors started significantly faster over the first 200 m of each of the three 1-km running stages. The last third of the approximately 3-km race was completed significantly faster by all athletes (P < 0.05). The main finding was that the best performers of the combined event distinguished themselves due to their greater shooting accuracy.

Influence of joint angle on muscle fascicle dynamics and rate of torque development during isometric explosive contractions.

This study investigated how joint angle influences fascicle shortening dynamics of gastrocnemius medialis (GM) during explosive contractions and the resulting impact on rate of torque development (RTD). Sixteen participants performed six sets of five maximal explosive voluntary isometric plantar flexions at -20°, -10°, 0° (neutral position), 10°, 20°, and 30° of ankle angle and five no-load ballistic plantar flexions. RTD assessed over all time windows (from 0 to 200 ms) was significantly lower in extreme plantar flexed (≥20°) and dorsiflexed (-20°) positions compared with -10, 0° (475 ± 105 N·m·s-1), and 10°. At these neutral positions, RTD was maximal and muscle fascicles mainly operated over the plateau of the force-length relationship. At 0°, fascicle shortening velocity peaked at 9.26 ± 2.85 cm/s (i.e., 28.2% of maximal shortening velocity measured during no-load ballistic condition). At 112 ms after RTD onset, fascicle force reached 208 ± 78 N (i.e., 85.6% of the theoretical maximum force at the corresponding shortening velocity) and was thereafter comprised within the 95% confidence interval of the force-velocity curve. This clearly indicates that muscle force reached the maximal force that accounts for the fascicle shortening velocity. These findings suggest that the dynamic behavior of muscle fascicles, and the associated fascicle shortening velocity, may influence the rapid force-generating capacity mainly from 100 ms of RTD onset. The present study provides important information for better understanding of the determinants of human muscle performance during explosive tasks.NEW & NOTEWORTHY Ankle angle influences the operating muscle fascicle lengths of gastrocnemius medialis and the rate of torque development during explosive isometric plantar flexions. The rate of torque development peaks in neutral angles where muscle fascicles shorten over the plateau of the force-length relationship. When fascicles operate over the plateau of the force-length relationship (neutral ankle positions), the force-velocity properties represent a limiting factor for the rapid force-generating capacity from 100 ms after the onset of explosive contractions.

Influence of gender on pacing adopted by elite triathletes during a competition.

The aim of this study was to compare the pacing strategies adopted by women and men during a World Cup ITU triathlon. Twelve elite triathletes (6 females, 6 males) competed in a World Cup Olympic distance competition where speed and heart rate (HR) were measured in the three events. The power output (PO) was recorded in cycling to determine the time spent in five intensity zones ([0-10% VT1]; [10% VT1-VT1]; [VT1-VT2]; [VT2-MAP] and > or =MAP) [ventilatory threshold (VT); maximal aerobic power (MAP)]. Swimming and running speeds decreased similarly for both genders (P < 0.05) and HR values were similar through the whole race (92 +/- 2 and 92 +/- 3% of maximal HR for women and men, respectively). The distribution of time spent in the five zones during the cycling leg was the same for both genders. The men's speed and PO decreased after the first bike lap (P < 0.05) and the women spent relatively more time above MAP in the hilly sections (45 +/- 4 vs. 32 +/- 4%). The men's running speed decreased significantly over the whole circuit, whereas the women slowed only over the uphill and downhill sections (P < 0.05). This study indicates that both female and male elite triathletes adopted similar positive pacing strategies during swimming and running legs. Men pushed the pace harder during the swim-to-cycle transition contrary to the women and female triathletes were more affected by changes in slope during the cycling and running phases.