Neural Adjustments during Repeated Braking and Throttle Actions on a Motorcycle Setup.

The aim of the study was to assess neuromuscular changes during an intermittent fatiguing task designed to replicate fundamental actions and ergonomics of road race motorcycling. Twenty-eight participants repeated a sequence of submaximal brake-pulling and gas throttle actions, interspaced by one maximal brake-pulling, until failure. During the submaximal brake-pulling actions performed at 30% MVC, force fluctuations, surface EMG, maximal M-wave (Mmax) and H-reflex were measured in the flexor digitorum superficialis. At the end of the task, the MVC force and associated EMG activity decreased (P<0.001) by 46% and 26%, respectively. During the task, force fluctuation and EMG activity increased gradually (106% and 61%, respectively) with respect to the pre-fatigue state (P≤0.029). The Mmax first phase did not change (P≥0.524), whereas the H-reflex amplitude, normalized to Mmax, increased (149%; P≤0.039). Noteworthy, the relative increase in H-reflex amplitude was correlated with the increase in EMG activity during the task (r=0.63; P<0.001). During the 10-min recovery, MVC force and EMG activity remained depressed (P≤0.05) whereas H-reflex amplitude and force fluctuation returned to pre-fatigue values. In conclusion, contrarily to other studies, our results bring forward that when mimicking motorcycling brake-pulling and gas throttle actions, supraspinal neural mechanisms primarily limit the duration of the performance.

Benefits of Training the Iron Cross With Herdos Devices and External Load Added to Body Weight for Young Nonachiever Gymnasts.

PURPOSE: To verify whether training the iron cross (IC) with assistive devices (herdos; HIC) and added external load (LHIC) to equate the moments of force developed on the rings could be considered an intermediate step between the nonoverloaded herdos situation (HIC) and the IC performed on the rings. METHODS: Relative levels of surface electromyography (sEMG) activity were normalized with respect to a standing IC before comparing gymnasts who can perform the IC on the rings (achievers) and gymnast who cannot (nonachievers) in the 2 herdos conditions (HIC and LHIC). Seven muscles were chosen for sEMG analysis, namely, pectoralis major (PM), latissimus dorsi, teres major, lower trapezius, serratus anterior, biceps brachii (BB), and triceps brachii. Additionally, 3 indices were calculated to measure levels of coactivation: Elbowidx, Scapulaidx, and Shoulderidx. RESULTS: The bigger magnitude of differences in sEMG activity among situations was found for the PM and BB (F ≥ 30.7; P < .001). When comparing the global and the PM, teres major, BB, and triceps brachii activity across groups, nonachievers activated their musculature to a greater extent than the achievers independently of the herdos situation (P ≤ .046). Achievers' Elbowidx was the only index that was significantly higher (P ≤ .005) in the IC in comparison to LHIC and HIC. CONCLUSION: sEMG activity of PM and BB was particularly sensitive between situations, independently of the level of achievement. We recommend training the IC by adding external load in the herdos situation to increase muscle activity to levels closer to the rings situation but avoiding the potential factor of injuries.

Exploring forearm muscle coordination and training applications of various grip positions during maximal isometric finger dead-hangs in rock climbers.

Background: Maximal isometric finger dead-hangs are used in rock climbing to strengthen finger flexors. Although various grip positions are often used when performing finger dead-hangs, little is known regarding how these grip positions can affect forearm muscle activity. Understanding how forearm muscles are recruited during dead-hangs could help foreseeing the potential for training of different grip positions. The aim of the present study was to explore the training applications of the various grip positions by comparing the activity of forearm muscles during maximal dead-hangs in rock climbers. Materials & Methods: Twenty-five climbers performed maximal dead-hangs in three climbing-specific grip positions: CRIMP, SLOPE, and SLOPER. We recorded the maximal loads used and the sEMG of the flexor digitorum profundus (FDP), the flexor digitorum superficialis (FDS), the flexor carpi radialis (FCR), and the extensor digitorum communis (EDC). Individual and global (sum of all muscles) root mean square (RMS) and neuromuscular efficiency (NME) values were computed. Repeated measures analysis were performed to assess grip differences (p < 0.05). Results: SLOPER showed the largest maximal load values among the three grip positions (p < 0.001, d ≥ 2.772). Greater global (p ≤ 0.044, d ≥ 0.268), FDS (p ≤ 0.005, d ≥ 0.277), and FCR (p < 0.001, d ≥ 1.049) activity was observed for the SLOPER compared to CRIMP and SLOPE, while EDC (p ≤ 0.005, d ≥ 0.505) showed lower activity in the SLOPER compared to the other two grip positions. SLOPER presented the highest global (p < 0.001, d ≥ 0.629), FDP (p < 0.001, d ≥ 0.777), FDS (only CRIMP vs SLOPER: p < 0.001, d = 0.140), and EDC NME (p < 0.001, d ≥ 1.194). The CRIMP showed greater FDS activity (p = 0.001, d = 0.386) and lower NME (p = 0.003, d = 0.125) compared to SLOPE. Conclusions: These results revealed that, under maximum intensity conditions, SLOPER could stimulate the FDS and FCR better than the other grip positions at the expense of using greater loads. Similarly, maximum CRIMP dead-hang could better stimulate the FDS than the SLOPE, even when using similar loads.

Changes of agonist and synergist muscles activity during a sustained submaximal brake-pulling gesture.

We analyzed the time course of changes in muscle activity of the prime mover and synergist muscles during a sustained brake-pulling action and investigated the relationship between muscle activity and braking force fluctuation (FF). Thirty-two participants performed a continuous fatiguing protocol (CFP) at 30% of maximal voluntary contraction (MVC) until failure. Surface electromyography was used to analyze root mean square (RMS) values in the flexor digitorum superficialis (FD), flexor carpi radialis (FC), extensor digitorum communis (ED), extensor carpi radialis (EC), brachioradialis (BR), biceps brachii (BB), and triceps brachii (TB). The FF and RMS in all muscles increased progressively (P<0.01) during the CFP, with sharp increments at time limit particularly in FD and FC (P<0.001). The RMS of the FD and FC were comparable to the baseline MVC values at time limit, in comparison to the other muscles that did not reach such levels of activity (P<0.003). The three flexor/extensor ratios used to measure coactivation levels decreased significantly (P<0.001). In contrast to RMS, MVC was still depressed at the minute 10 of recovery. The results suggest that the time limit was mainly constrained by fatigue-related mechanisms of the FD and FC but not by those of other synergist and antagonist muscles.

Muscle Fatigue When Riding a Motorcycle: A Case Study.

This case study was conducted to assess muscle pattern, as measured by surface electromyography (sEMG), and its changes during a controlled superbike closed-road track training session. The sEMG signals were recorded unilaterally from biceps brachii (BB), triceps brachii (TB), anterior and posterior part of the deltoid (DA and DP respectively), flexor digitorum superficialis (FS), extensor carpi radialis (CR), extensor digitorum communis (ED) and pectoralis major (PM) during three rounds of 30 min. sEMG signals selected for analysis came from the beginning of the braking action to the way-out of the curves of interest. Considering the laps and rounds as a whole and focusing on the forearm muscles, ED was more systematically (84%) assigned to a state of fatigue than FS (44%) and CR (39%). On the opposite, the TB and DP muscles showed a predominant state of force increase (72%). Whereas the BB showed alternatively a state of fatigue or force increase depending on the side of the curve, when taking into account only the sharpest curves, it showed a predominant state of force increase. In conclusion, the fact that forearm muscles must endure a long-lasting maintenance of considerable activity levels explains why they easily got into a state of fatigue. Moreover, TB and DA are particularly relevant when cornering.

Recovery and Fatigue Behavior of Forearm Muscles during a Repetitive Power Grip Gesture in Racing Motorcycle Riders.

Despite a reduction in the maximal voluntary isometric contraction (MVCisom) observed systematically in intermittent fatigue protocols (IFP), decrements of the median frequency, assessed by surface electromyography (sEMG), has not been consistently verified. This study aimed to determine whether recovery periods of 60 s were too long to induce a reduction in the normalized median frequency (MFEMG) of the flexor digitorum superficialis and carpi radialis muscles. Twenty-one road racing motorcycle riders performed an IFP that simulated the posture and braking gesture on a motorcycle. The MVCisom was reduced by 53% (p < 0.001). A positive and significant relationship (p < 0.005) was found between MFEMG and duration of the fatiguing task when 5 s contractions at 30% MVCisom were interspersed by 5 s recovery in both muscles. In contrast, no relationship was found (p > 0.133) when 10 s contractions at 50% MVC were interspersed by 1 min recovery. Comparative analysis of variance (ANOVA) confirmed a decrement of MFEMG in the IFP at 30% MVCisom including short recovery periods with a duty cycle of 100% (5 s/5 s = 1), whereas no differences were observed in the IFP at 50% MVCisom and longer recovery periods, with a duty cycle of 16%. These findings show that recovery periods during IFP are more relevant than the intensity of MVCisom. Thus, we recommend the use of short recovery periods between 5 and 10 s after submaximal muscle contractions for specific forearm muscle training and testing purposes in motorcycle riders.

Forearm muscles fatigue induced by repetitive braking on a motorcycle is best discriminated by specific kinetic parameters.

Maneuvering a motorcycle in racing conditions or for prolonged time is sufficiently demanding that on many occasions forearm muscles reach a state of functional failure when riders cannot properly brake or operate the throttle. This study intends to discriminate which ones of the several dynamometric parameters used in the literature to characterize the Force-time (F-t) curve during voluntary contractions are more sensitive to neuromuscular fatigue in simulated motorcycle-riding conditions. Thirty-three adults performed an intermittent fatiguing protocol (IFP) that simulated the brake-pulling and throttle-twisting actions, by using a hydraulic system equipped with a pressure sensor. Sixty pressure-time (P-t) curve parameters, including the rate of pressure development (RPD) and area under the curve were measured to characterize the time course of the braking maximal voluntary contraction (MVC). Two types of variables were used to analyze the P-t curve: 1) Times interval (from 0 to 30-50-100-500-1000 and 2000 ms); 2) Percentages of MVC (10-30-60-90%MVC). Overall significant (p ≤ 0.05) fatigue-related declines were observed only at time intervals longer than 100 ms and contraction intensities higher than 30%MVC. Strong and significant linear declines (p < 0.001) were observed at 500 ms and 1 s for normalized pressures, as well as for the ratio RPD60%MVC/MVC (p < 0.003) throughout the IFP. Our results suggest considering RPD at time windows of 0-500 ms and 0-1 s, and contraction intensities comprised between 30% and 60% of MVC, as more suitable criteria to study fatigue-related decrements in performance rather than the classical MVC force.

Does gymnastics practice improve vertical jump reliability from the age of 8 to 10 years?

The objective of this study was to confirm whether gymnastics practice from a young age can induce greater vertical jump reliability. Fifty young female gymnasts (8.84 ± 0.62 years) and 42 females in the control group (8.58 ± 0.92 years) performed the following jump tests on a contact mat: squat jump, countermovement jump, countermovement jump with arm swing and drop jump from heights of 40 and 60 cm. The two testing sessions had three trials each and were separated by one week. A 2 (groups) × 2 (sessions) × 3 (trials) repeated measures analysis of variance (ANOVA) and a test-retest correlation analysis were used to study the reliability. There was no systematic source of error in either group for non-plyometric jumps such as squat jump, countermovement jump, and countermovement jump with arm swing. A significant group per trial interaction revealed a learning effect in gymnasts' drop jumps from 40 cm height. Additionally, the test-retest correlation analysis and the higher minimum detectable error suggest that the quick drop jump technique was not fully consolidated in either group. At an introductory level of gymnastics and between the ages of 8-10 years, the condition of being a gymnast did not lead to conclusively higher reliability, aside from better overall vertical jump performance.

High energy deficit in an ultraendurance athlete in a 24-hour ultracycling race.

This case study examined the nutritional behavior and energy balance in an official finisher of a 24-hour ultracycling race. The food and beverages consumed by the cyclist were continuously weighed and recorded to estimate intake of energy, macronutrients, sodium, and caffeine. In addition, during the race, heart rate was continuously monitored. Energy expenditure was assessed using a heart rate-oxygen uptake regression equation obtained previously from a laboratory test. The athlete (39 years, 175.6 cm, 84.2 kg, maximum oxygen uptake, 64 mL/kg/min) cycled during 22 h 22 min, in which he completed 557.3 km with 8760 m of altitude at an average speed of 25.1 km/h. The average heart rate was 131 beats/min. Carbohydrates were the main macronutrient intake (1102 g, 13.1 g/kg); however, intake was below current recommendations. The consumption of protein and fat was 86 g and 91 g, respectively. He ingested 20.7 L (862 mL/h) of fluids, with sport drinks the main fluid used for hydration. Sodium concentration in relation to total fluid intake was 34.0 mmol/L. Caffeine consumption over the race was 231 mg (2.7 mg/kg). During the race, he expended 15,533 kcal. Total energy intake was 5571 kcal, with 4058 (73%) and 1513 (27%) kcal derived from solids and fluids, respectively. The energy balance resulted in an energy deficit of 9915 kcal.

Nutritional behavior of cyclists during a 24-hour team relay race: a field study report.

BACKGROUND: Information about behavior of energy intake in ultra-endurance cyclists during a 24-hour team relay race is scarce. The nutritional strategy during such an event is an important factor which athletes should plan carefully before the race. The purpose of this study was to examine and compare the nutritional intake of ultra-endurance cyclists during a 24-hour team relay race with the current nutritional guidelines for endurance events. Additionally, we analyzed the relationship among the nutritional and performance variables. METHODS: Using a observational design, nutritional intake of eight males (mean ± SD: 36.7 ± 4.7 years; 71.6 ± 4.9 kg; 174.6 ± 7.3 cm; BMI 23.5 ± 0.5 kg/m2) participating in a 24-hour team relay cycling race was assessed. All food and fluid intake by athletes were weighed and recorded. Additionally, distance and speed performed by each rider were also recorded. Furthermore, before to the race, all subjects carried out an incremental exercise test to determine two heart rate-VO2 regression equations which were used to estimate the energy expenditure. RESULTS: The mean ingestion of macronutrients during the event was 943 ± 245 g (13.1 ± 4.0 g/kg) of carbohydrates, 174 ± 146 g (2.4 ± 1.9 g/kg) of proteins and 107 ± 56 g (1.5 ± 0.7 g/kg) of lipids, respectively. This amount of nutrients reported an average nutrient intake of 22.8 ± 8.9 MJ which were significantly lower compared with energy expenditure 42.9 ± 6.8 MJ (P = 0.012). Average fluid consumption corresponded to 10497 ± 2654 mL. Mean caffeine ingestion was 142 ± 76 mg. Additionally, there was no relationship between the main nutritional variables (i.e. energy intake, carbohydrates, proteins, fluids and caffeine ingestion) and the main performance variables (i.e. distance and speed). CONCLUSIONS: A 24-hour hours cycling competition in a team relay format elicited high energy demands which were not compensated by energy intake of the athletes despite that dietary consumption of macronutrients did not differ to the nutritional guidelines for longer events.

Physiological demands of cyclists during an ultra-endurance relay race: a field study report.

This study was to describe and compare the physiological demands of ultra-endurance cyclists during a 24 h cycling relay race. Eleven male athletes (means +/- SD: 34.8 +/- 5.6 years; 71.6 +/- 4.9 kg; 174.6 +/- 7.3 cm; BMI 23.5 +/- 0.5 kg/m2; VO2 max: 66.0 +/- 6.4 ml/kg/min) participated in the study; eight in teams with a format of four riders (4C) and three in teams with six riders (6C). To investigate exercise intensity, heart rate (HR) was recorded while cycling using portable telemetric monitors. Three different exercise intensities were defined according to the reference HR values obtained during a pre race laboratory incremental VO2 max test: Zone I (< anaerobic threshold [AT]), Zone II (between AT and the respiratory compensation point [RCP]), Zone III (> RCP). Total volume and intensity were integrated as a single variable (training impulse: TRIMP). The score for TRIMP in each zone was computed by multiplying the accumulated duration in this zone by a multiplier for this particular zone of exercise intensity. The average intensity did not differ between cyclists in 4C (means +/- SD; 4C: 87 +/- 3 HRmax) and 6C (87 +/- 1% of HRmax), despite the higher volume performed by 4C (means +/- SD; 4C: 361 +/- 65; 6C: 242 +/- 25 per min; P = 0.012). These differences in total exercise volume significantly affected the values TRIMP accumulated (means +/- SD; 4C: 801 +/- 98, confidence interval [CI] 95%: 719 - 884; 6C: 513 +/- 25, CI 95%: 451 - 575; P = 0.012). The ultra-endurance threshold of 4C and 6C athletes lies at about 87% of HRmax for both. Although the intensity profile was similar, the TRIMP values differed significantly as a consequence of the higher volume performed by the 4C cyclists.