PRE-EXERCISE CARBOHYDRATE ADMINISTRATION: EFFECT OF TIMING ON THE RATE OF GLYCOGEN METABOLISM DURING SUBMAXIMAL RUNNING

The aim of this study was to investigate the metabolic responses of the timing of preexercise carbohydrate feeding. Nine moderately trained runners, 7 men, and 2 women, performed an incremental test to exhaustion followed by three 6 min running trials at 75% VO2max on the treadmill. The submaximal runs were performed after ingestion a placebo solution (PLA) one hour before or CHO solution 1gr.kgBM-1 one (CHO60) or two hours (CHO120) before the trial. All trials were performed at least 2 days apart in a double-blind cross-over design following an overnight fast. The results showed no significant differences in physiological parameters (VO2, RER, HR) and CHO metabolism between the three conditions. Blood glucose concentration immediately before the 6-min trials was higher after CHO60 (1.22±0.23 gr.L-1) compared to CHO120 (0.93±0.10 gr.L-1) conditions (p=0.007, η2= 0.567). These findings suggest that preexercise timing of CHO ingestion results in significantly different blood glucose concentrations prior to submaximal running, with no further metabolic and physiological alterations.  Article visualizations

Effect of a Carbohydrate-Electrolyte Solution on Fluid Balance and Performance at a Thermoneutral Environment in International-Level Fencers

© 2019 by the National Strength & Conditioning Association.Chryssanthopoulos, C, Tsolakis, C, Bottoms, L, Toubekis, A, Zacharogiannis, E, Pafili, Z, and Maridaki, M. Effect of a carbohydrate-electrolyte solution on fluid balance and performance at a thermoneutral environment in international-level fencers. J Strength Cond Res 34(1): 152-161, 2020-The purpose of the study was to examine a possible effect of a carbohydrate-electrolyte (CHO-E) solution on fluid balance and performance in fencing at a thermoneutral environment. Sixteen fencers performed two 120-minute training sessions separated by 7-14 days under similar environmental conditions (temperature: 20.3° C and humidity: 45-47%). Each session consisted of 60-minute conditioning exercises followed by 10 bouts of 3 minutes against the same opponent with 3-minute interval between each bout. Participants ingested at regular intervals either a 6% CHO-E solution or an artificially sweetened water (PL) in a counterbalanced order. No difference was observed between conditions in the heart rate responses, perceived exertion, changes in plasma volume, urine specific gravity, number of bouts won or lost, or points for and against. Considerable variability was observed in body mass changes that revealed significant differences at the time level (i.e., pre- vs. post-exercise) (F1,15 = 9.31, p = 0.008, η = 0.38), whereas no difference was found between conditions (i.e., CHO-E vs. PL) (F1,15 = 0.43, p = 0.52, η = 0.03) and conditions × time interaction (F1,15 = 3.57, p = 0.078, η = 0.19). Fluid loss was not significantly different between conditions (p = 0.08, d = 0.47). The blood glucose level was higher (p < 0.01) after exercise in CHO-E, whereas the blood lactate level was similar between conditions. In conclusion, the CHO-E solution was as effective as the artificially sweetened water in terms of fluid balance and fencing performance at a thermoneutral environment. Because of large individual variability, fencers should monitor their fluid intake and body fluid loss in training and competition.Peer reviewedFinal Accepted Versio

FORCE-VELOCITY RELATIONSHIP BETWEEN SPRINTING AND JUMPING TESTING PROCEDURES

The aim of this study was to examine the relationship between the mechanical characteristics of the horizontal and vertical Force-velocity (F-v) profile as well as the performance variables of the sprinting and jumping testing procedures. Twenty high-level sprinters performed two maximal sprints and squat jumps against multiple external loads. Our main findings revealed very large correlations for maximal mechanical power output (Pmax) (r=0.72), as well as for performance variables between the sprinting and jumping tasks (r=-0.81) and large correlations for maximal velocity (V0) (r=0.66). The maximal force (F0) and the slope of the F-v relationship (F-v slope) were not significantly correlated between both tasks. These results suggest that both testing procedures should be performed in order to gain a deeper insight into the maximal mechanical properties and function of the lower-body muscles in high-level sprinters

TIME TO EXHAUSTION AT 90 AND 100% VO2MAX AND PHYSIOLOGICAL DETERMINANTS OF 3 KM PERFORMANCE IN ELITE CYCLISTS

The minimal power that elicits VO2max and the time to exhaustion (tlimit) at this workload appear to determine cyclists’ endurance capabilities, analyze performance and help coaches to design training. Data in the literature are limited so as to elucidate this. The aim of this study was to investigate the tlimit at the power output, which corresponds to 90 (tlimit 90) and 100% VO2max (tlimit 100) in elite endurance cyclists. The contribution of tlimit in 3 km indoor individual time trial was also studied. Subjects were eleven elite male road cyclists (age 17.7 0.5 years, body mass 66.8 4.9 kg, body height 176.3 7.4 cm, VO2max 69.77 2.58 ml.kg-1.min-1). Power output at 90 and 100% VO2max was determined by continuous incremental testing. This protocol had steps of 2 min and increments of 30 W. The exhaustive trials tlimit 90 or tlimit 100 were performed in random order at least five days apart. Five days after the last exhaustive trial, cyclists performed an individual 3 km time trial on an indoor wooden track. Mean sd, tlimit 90 and tlimit 100 were 16:27.73 07:46.6 and 4:48.6 00:53.2 min:sec. Time to exhaustion at tlimit 90 and tlimit 100 ranged between 07:00-30:15 and 03:10-06:00 min:sec, respectively. Tlimit 100, tlimit 90 and VO2max (ml.min-1) did not correlate with 3 km cycling performance (r = 0.08, 0.16 and –0.59, p > 0.05). Tlimit 90 was inversely related (r = –0.49, p = 0.1) with VO2max (ml.min-1). Only power output which corresponded to ventilatory threshold and VO2max correlated significantly with 3 km performance (r = –0.83 and –0.80, p < 0.01). The results of this study indicate that: a) if cyclists’ training intensity is based on %VO2max, individual determination of the tlimit at the %VO2max has to be considered due to a wide range of tlimit to exhaustion; b) 3 km performance directly depends on the power that corresponds with ventilatory threshold and VO2max. Article visualizations

PHYSIOLOGICAL DETERMINANTS OF SHORT TRAIL RUNNING

The recent worldwide popularity of trail running has raised the necessity of studying the physiological profile of this sport. Although trail running races are long distance endurance events, the variety of their terrain, incline and duration prevents the application of the classical predictive model of level running. Thus, the aim of the present study was to investigate the physiological and anthropometric parameters that determine short trail race performance. Twenty-five moderately trained trail runners participated in a 15 km trail running race, consisting of 9 km positive and 6 km negative incline. Four days after the race they followed a laboratory protocol for the measurement and estimation of anthropometric and physiological parameters (maximal oxygen uptake, velocity at maximal oxygen uptake, ventilatory threshold, velocity at ventilatory threshold, running economy, flexibility, muscle power, aerobic capacity). The results revealed high correlations between the 15 km race performance and velocity at maximal oxygen uptake (r = 0.81), ventilatory threshold (r = 0.88), muscle power of knee extensor (r = 0.50 – 0.53), anaerobic capacity (r = 0.65) and body fat percentage (r = 0.7). Another two parameters that were highly correlated with the 15 km mountain trail race performance were both the positive and negative incline time (r = 0.95 and r = 0.96, respectively). Our conclusions confirmed previous findings that performance in trail running cannot be predicted with the same variable model as level running.  Article visualizations

Sprint mechanical differences at maximal running speed: Effects of performance level

The aim of this study was to analyze footstrike patterns in elite marathon runners at the 2017 IAAF World Championships. Seventy-one men and 78 women were analyzed in their respective races. Athletes’ footstrike patterns were recorded (120 Hz) at approximately 8.5, 19, 29.5 and 40 km (“Laps 1 – 4”) and categorized as either rearfoot (RFS), midfoot or forefoot striking; the latter two were classified together as non-rearfoot striking (NRFS). The most common footstrike pattern was RFS, with proportions never less than 54% of men or 67% of women at any distance. There were no sex-based differences for proportion of footstrike patterns, and there were no differences between footstrike proportions when comparing the top and bottom 50% of men finishers, or between women during Laps 1 and 2. A greater proportion of the top 50% of women maintained NRFS than amongst the bottom 50%. The proportion of RFS increased with distance run in the men’s race, although more than 75% of athletes across both marathons had consistent footstrike patterns between laps (79 RFS and 36 NRFS). As most athletes were RFS (including the top four finishing men), there appears to be no clear advantage to NRFS in marathon running. Coaches should note that it is normal for elite marathon runners to be either RFS or NRFS; however, forefoot striking was rare. The high proportion of athletes who maintained their footstrike pattern reflected individualized preferences for a given footstrike pattern

EFFECTS OF WHOLE-BODY VIBRATION TRAINING ON SPRINT RUNNING KINEMATICS AND EXPLOSIVE STRENGTH PERFORMANCE

The aim of this study was to investigate the effect of 6 wk of whole body vibration (WBV) training on sprint running kinematics and explosive strength performance. Twenty-four volunteers (12 women and 12 men) participated in the study and were randomised (n = 12) into the experimental and control groups. The WBV group performed a 6-wk program (16-30 min·d-1, 3 times a week) on a vibration platform. The amplitude of the vibration platform was 2.5 mm and the acceleration was 2.28 g. The control group did not participate in any training. Tests were performed Pre and post the training period. Sprint running performance was measured during a 60 m sprint where running time, running speed, step length and step rate were calculated. Explosive strength performance was measured during a counter movement jump (CMJ) test, where jump height and total number of jumps performed in a period of 30 s (30CVJT). Performance in 10 m, 20 m, 40 m, 50 m and 60 m improved significantly after 6 wk of WBV training with an overall improvement of 2.7%. The step length and running speed improved by 5.1% and 3.6%, and the step rate decreased by 3.4%. The countermovement jump height increased by 3.3%, and the explosive strength endurance improved overall by 7.8%. The WBV training period of 6 wk produced significant changes in sprint running kinematics and explosive strength performanc

Assessment of accuracy, reliability and force measurement errors for a tethered swimming apparatus

Researchers frequently use purpose-built devices to calculate propulsive forces during tethered swimming. Although such devices are subject to force measurement errors, no specific methods have been suggested in the swimming literature for the estimation of these errors. The purpose of this study was to access the accuracy and reliability of a portable device that is used to measure propulsive forces in tethered swimming, and to estimate the errors caused by hysteresis, sensitivity and linearity. The force values recorded during a maximum front crawl test of an international level swimmer were used to provide an example of the extent to which measurement errors could affect the values collected during a tethered swimming study. The calculations revealed small and acceptable errors. When summing the errors from all sources, the total errors affecting the minimum, average and peak forces recorded during the case study were 1.15%, 0.94% and 0.86% respectively. It is recommended that investigators always calculate and report such errors for tethered swimming studies. The methods used in the present study are reasonably simple and not time-consuming, and could be used when assessing errors for similar tethered swimming devices