Relationships among field-test measures and physical match performance in elite-standard soccer referees

Abstract

The aim of this study was to assess the extent to which measures derived from the new FIFA referees’ fitness tests can be used to monitor a referee's match-related physical capacity. Match-analysis data were collected (Prozone®, Leeds, UK) from 17 soccer referees for 5.0 (s = 1.7) FA Premier League matches per referee during the first 4 months of the 2007–08 season. Physical match performance categories included total distance covered, high-intensity running distance (speed >5.5 m · s^?1), and sprinting distance (>7.0 m · s^?1). The two tests were a 6 × 40-m sprint test and a 150-m interval test. Heart rate demand was correlated with total match distance covered (r = ?0.70, P = 0.002) and high-intensity running (r = ?0.57, P = 0.018) in the interval test. The fastest 40-m sprint was related to total distance covered (r = ?0.69, P = 0.002), high-intensity running (r = ?0.76, P < 0.001), and sprinting distance (r = ?0.75, P = 0.001), while mean time for the 40-m sprints was related to total distance covered (r = ?0.70, P = 0.002), high-intensity running (r = ?0.77, P < 0.001), and sprinting distance (r = ?0.77, P < 0.001). The referees who recorded the best interval-test heart rate demand and fastest 40-m time produced the best physical match performances. However, only the sprint test and in particular the fastest 40-m time had appropriate construct validity for the physical assessment of soccer referees.     

Influence of football match time–motion parameters on recovery time course of muscle damage and jump ability

ABSTRACT

We analysed the time course of recovery of creatine kinase (CK) and countermovement jump (CMJ) parameters after a football match, and correlations between changes in these variables and match time–motion parameters (GPS-accelerometry) in 15 U-19 elite male players. Plasma CK and CMJ height (CMJ_H), average concentric force (CMJ_CON) and average eccentric force (CMJ_ECC) were assessed 2 h before and 30 min, 24 h and 48 h post-match. There were substantially higher CK levels 30 min, 24 h and 48 h (ES: 0.43, 0.62, 0.40, respectively), post-match. CMJ_ECC (ES: ?0.38), CMJ_H (ES: ?0.35) decreased 30 min post, CMJ_CON (ES: ?0.35), CMJ_ECC (ES: ?0.35) and CMJ_H (ES: ?1.35) decreased 24 h post, and CMJ_CON (ES: ?0.41) and CMJ_H (ES: ?0.53) decreased 48 h post. We found correlations between distance covered at velocities ≤21 km · h^?1 and changes in CK at 24 h (r = 0.56) and at 48 h (r = 0.54) and correlations between CK and distance covered >14 km · h^?1 (r = 0.50), accelerations (r = 0.48), and decelerations (r = 0.58) at 48 h. Changes in CMJ_CON 30 min and 24 h post (both r = ?0.68) correlated with impacts >7.1·G. Decelerations >2 m · s^?2 correlated with changes CMJ_CON (r = ?0.49) at 48 h and CMJ_ECC (r = ?0.47) at 30 min. Our results suggest that match GPS-accelerometry parameters may predict muscle damage and changes in components of neuromuscular performance immediately and 24–48 h post-match.     

Match activity and physiological load during a clay-court tennis tournament in elite female players

Abstract

The aim of this study was to determine the match activity and physiological demands of women's tennis during a 3-day clay-court tennis tournament. The activity profile of eight players was determined by filming each competitive match with video cameras. Metabolic-perceptual measurements–blood samples and individual ratings of perceived exertion (RPE)–were taken while the players were sitting during permitted changeover breaks in play. The activity profile of the players was as follows: strokes per rally, 2.5 ± 1.6; rally duration, 7.2 ± 5.2 s; rest time between rallies, 15.5 ± 7.3 s; effective playing time, 21.6 ± 6.1%; work-to-rest ratio, 1:2.1. Blood lactate concentration [2.2 ± 0.9 mmol · l^?1 (n = 50) vs. 2.2 ± 0.7 mmol · l^?1 (n = 48)] and RPE values [12.2 ± 2.4 (n = 57) vs. 12 ± 2.3 (n = 57)] were not significantly different (P = 0.65–0.78) between service and return games. The results highlight the importance of taking these factors (i.e. activity patterns and physiological profile) into account when planning training strategies for competitive females players. As such, tennis training regimes should be adapted to the specific demands imposed by match-play in female players on a clay-court surface.     

Core stability training on lower limb balance strength

This study aimed to assess the effects of core stability training on lower limbs’ muscular asymmetries and imbalances in team sport. Twenty footballers were divided into two groups, either core stability or control group. Before each daily practice, core stability group (n = 10) performed a core stability training programme, while control group (n = 10) did a standard warm-up. The effects of the core stability training programme were assessed by performing isokinetic tests and single-leg countermovement jumps. Significant improvement was found for knee extensors peak torque at 3.14 rad · s^?1 (14%; P < 0.05), knee flexors peak torque at 1.05 and 3.14 rad · s^?1 (19% and 22% with P < 0.01 and P < 0.01, respectively) and peak torque flexors/extensors ratios at 1.05 and 3.14 rad · s^?1 (7.7% and 8.5% with P < 0.05 and P < 0.05, respectively) only in the core stability group. The jump tests showed a significant reduction in the strength asymmetries in core stability group (?71.4%; P = 0.02) while a concurrent increase was seen in the control group (33.3%; P < 0.05). This study provides practical evidence in combining core exercises for optimal lower limbs strength balance development in young soccer players.     

The multi-stage fitness test as a predictor of endurance fitness in wheelchair athletes

Abstract

The aims of this study were two-fold: (1) to consider the criterion-related validity of the multi-stage fitness test (MSFT) by comparing the predicted maximal oxygen uptake ([Vdot]O_2max) and distance travelled with peak oxygen uptake ([Vdot]O_2peak) measured using a wheelchair ergometer (n = 24); and (2) to assess the reliability of the MSFT in a sub-sample of wheelchair athletes (n = 10) measured on two occasions. Twenty-four trained male wheelchair basketball players (mean age 29 years, s = 6) took part in the study. All participants performed a continuous incremental wheelchair ergometer test to volitional exhaustion to determine [Vdot]O_2peak, and the MSFT on an indoor wooden basketball court. Mean ergometer [Vdot]O_2peak was 2.66 litres · min^?1 (s = 0.49) and peak heart rate was 188 beats · min^?1 (s = 10). The group mean MSFT distance travelled was 2056 m (s = 272) and mean peak heart rate was 186 beats · min^?1 (s = 11). Low to moderate correlations (ρ = 0.39 to 0.58; 95% confidence interval [CI]: ?0.02 to 0.69 and 0.23 to 0.80) were found between distance travelled in the MSFT and different expressions of wheelchair ergometer [Vdot]O_2peak. There was a mean bias of ?1.9 beats · min^?1 (95% CI: ?5.9 to 2.0) and standard error of measurement of 6.6 beats · min^?1 (95% CI: 5.4 to 8.8) between the ergometer and MSFT peak heart rates. A similar comparison of ergometer and predicted MSFT [Vdot]O_2peak values revealed a large mean systematic bias of 15.3 ml · kg^?1 · min^?1 (95% CI: 13.2 to 17.4) and standard error of measurement of 3.5 ml · kg^?1 · min^?1 (95% CI: 2.8 to 4.6). Small standard errors of measurement for MSFT distance travelled (86 m; 95% CI: 59 to 157) and MSFT peak heart rate (2.4 beats · min^?1; 95% CI: 1.7 to 4.5) suggest that these variables can be measured reliably. The results suggest that the multi-stage fitness test provides reliable data with this population, but does not fully reflect the aerobic capacity of wheelchair athletes directly.     

Intensities of exercise during match-play in FA Premier League referees and players

Abstract

The aim of the present study was to examine the relationship between intensities of exercise during match-play of elite-standard soccer referees with those of the players from the same match. Match analysis data were collected (Prozone® Leeds, UK) for 18 elite-standard soccer referees (age 26–49 years) on FA Premier League matches during the 2008/09 English FA Premier League season (236 observations). Running categories for referees and players were as follows: total distance covered (m); high-speed running distance (speed >19.8 km · h^?1); and sprinting distance (speed >25.2 km · h^?1). Analysis of the distance–time regression coefficients revealed no differences between the referees' and players' within-match rates of change for total distance covered (?0.594 ± 0.394 vs. ?0.713 ± 0.269 m · min^?1; P = 0.104), high-speed running (?0.039 ± 0.077 vs. ?0.059 ± 0.030 m · min^?1; P = 0.199), and sprinting (?0.003 ± 0.039 vs. ?0.021 ± 0.017 m · min^?1; P = 0.114). In addition, there were no differences between across-season rates of change for total distance (–26.756 ± 40.434 vs. ?20.031 ± 25.502 m per match day; P = 0.439) and sprinting (–9.662 ± 7.564 vs. ?8.589 ± 4.351 m per match day; P = 0.542). These results show that elite-standard soccer referees' intensities of exercise during match-play are interrelated with those of the players and thus demonstrate that referees are able to keep pace with the players during FA Premier League matches.     

Effects of tapering on physical match activities in professional soccer players

ABSTRACT

This study aimed to examine: (i) the effect of decreasing training load (TL) during taper weeks on physical match activities in professional soccer players, and (ii) to disclose the relationship between weekly TL and physical match activities. Rating of perceived exertion was collected after each training session and match to quantify the TL in 19 professional players over 17 standard and 7 taper weeks during the season. Physical match activities were quantified by a computerised match analysis system and compared between standard training and taper weeks. Compared to standard weeks, the duration and frequency of training sessions during the taper weeks decreased (?21.7% and ?18.8%, respectively; P < 0.01) with no change in intensity (?4.8%; P = 0.09). Consequently, the weekly TL decreased during the taper weeks (?25.5%; P < 0.01). Increases in distance covered by intense running (+15.1%; P < 0.05), high-intensity running (HIR) (+15.7%; P < 0.01), number of sprints (+17.8%; P < 0.05) and number of high-speed runs (+15.7%; P < 0.05) were observed during the seven matches played after the taper weeks. High relationships were observed between TL and HIR distance covered, number of HIR and number of sprints (r = ?0.53; r = ?0.55; r = ?0.65, respectively; P < 0.01). Decreasing TL during taper weeks by reducing training duration and frequency but maintaining intensity was associated with an increase in physical activities during matches. However, it needs to be determined whether tapering or other match factors led to the changes in match activity.     

Development,construct validity and test–retest reliability of a field-based wheelchair mobility performance test for wheelchair basketball

The aim of this study was to develop and describe a wheelchair mobility performance test in wheelchair basketball and to assess its construct validity and reliability. To mimic mobility performance of wheelchair basketball matches in a standardised manner, a test was designed based on observation of wheelchair basketball matches and expert judgement.

Forty-six players performed the test to determine its validity and 23 players performed the test twice for reliability. Independent-samples t-tests were used to assess whether the times needed to complete the test were different for classifications, playing standards and sex. Intraclass correlation coefficients (ICC) were calculated to quantify reliability of performance times.

Males performed better than females (P < 0.001, effect size [ES] = ?1.26) and international men performed better than national men (P < 0.001, ES = ?1.62). Performance time of low (≤2.5) and high (≥3.0) classification players was borderline not significant with a moderate ES (P = 0.06, ES = 0.58). The reliability was excellent for overall performance time (ICC = 0.95).

These results show that the test can be used as a standardised mobility performance test to validly and reliably assess the capacity in mobility performance of elite wheelchair basketball athletes. Furthermore, the described methodology of development is recommended for use in other sports to develop sport-specific tests.     

The Dutch motor skills assessment as tool for talent development in table tennis: a reproducibility and validity study

A motor skills assessment could be helpful in talent development by estimating essential perceptuo-motor skills of young players, which are considered requisite to develop excellent technical and tactical qualities. The Netherlands Table Tennis Association uses a motor skills assessment in their talent development programme consisting of eight items measuring perceptuo-motor skills specific to table tennis under varying conditions. This study aimed to investigate this assessment regarding its reproducibility, internal consistency, underlying dimensions and concurrent validity in 113 young table tennis players (6–10 years). Intraclass correlation coefficients of six test items met the criteria of 0.7 with coefficients of variation between 3% and 8%. Cronbach’s alpha valued 0.853 for internal consistency. The principal components analysis distinguished two conceptually meaningful factors: “ball control” and “gross motor function.” Concurrent validity analyses demonstrated moderate associations between the motor skills assessment’s results and national ranking; boys r = ?0.53 (P < 0.001) and girls r = ?0.45 (P = 0.015). In conclusion, this evaluation demonstrated six test items with acceptable reproducibility, good internal consistency and good prospects for validity. Two test items need revision to upgrade reproducibility. Since the motor skills assessment seems to be a reproducible, objective part of a talent development programme, more longitudinal studies are required to investigate its predictive validity.     

Physiological characteristics of elite and sub-elite badminton players

Abstract

The aims of this study were to establish the physical and physiological attributes of elite and sub-elite Malaysian male badminton players and to determine whether these attributes discriminate elite players from sub-elite players. Measurements and tests of basic anthropometry, explosive power, anaerobic recovery capacity, badminton-specific movement agility, maximum strength, and aerobic capacity were conducted on two occasions, separated by at least one day. The elite (n = 12) and sub-elite (n = 12) players' characteristics were, respectively: mean age 24.6 years (s = 3.7) and 20.5 years (s = 0.7); mass 73.2 kg (s = 7.6) and 62.7 kg (s = 4.2); stature 1.76 m (s = 0.07) and 1.71 m (s = 0.05); body fat 12.5% (s = 4.8) and 9.5% (s = 3.4); estimated VO_2max 56.9 ml · kg^?1 · min^?1 (s = 3.7) and 59.5 ml · kg^?1 · min^?1 (s = 5.2). The elite players had greater maximum absolute strength in one-repetition maximum bench press (P = 0.015) compared with the sub-elite players. There were significant differences in instantaneous lower body power estimated from vertical jump height between the elite and sub-elite groups (P < 0.01). However, there was no significant difference between groups in shuttle run tests and on-court badminton-specific movement agility tests. Our results show that elite Malaysian male badminton players are taller, heavier, and stronger than their sub-elite counterparts. The test battery, however, did not allow us to discriminate between the elite and sub-elite players, suggesting that at the elite level tactical knowledge, technical skills, and psychological readiness could be of greater importance.     

Torque–velocity characteristics and contractile rate of force development in elite badminton players

Abstract

Elite badminton requires muscular endurance combined with appropriate maximal and explosive muscle strength. The musculature of the lower extremities is especially important in this context since rapid and forceful movements with the weight of the body are performed repeatedly throughout a match. In the present study, we examined various leg-strength parameters of 35 male elite badminton players who had been performing resistance exercises as part of their physical training for several years. The badminton players were compared with an age-matched reference group, the members of whom were physically active on a recreational basis, and to the same reference group after they had performed resistance training for 14 weeks. Maximal muscle strength of the knee extensor (quadriceps) and flexor muscles (hamstrings) was determined using isokinetic dynamometry. To measure explosive muscle strength, the contractile rate of force development was determined during maximal isometric muscle contractions. In general, the badminton players showed greater maximal muscle strength and contractile rate of force development than the reference group: mean quadriceps peak torque during slow concentric contraction: 3.69 Nm · kg^?1, s=0.08 vs. 3.26 Nm · kg^?1, s=0.8 (P<0.001); mean hamstring peak torque during slow concentric contraction: 1.86 Nm · kg^?1, s=0.04 vs. 1.63 Nm · kg^?1, s=0.04 (P<0.001); mean quadriceps rate of force development at 100 ms: 24.4 Nm · s^?1·kg^?1, s=0.5 vs. 22.1 Nm·s^?1 · kg^?1, s=0.6 (P<0.05); mean hamstring rate of force development at 100 ms: 11.4 Nm · s^?1·kg^?1, s=0.3 vs. 8.9 Nm · s^?1 · kg^?1, s=0.4 (P<0.05). However, after 14 weeks of resistance training the reference group achieved similar isometric and slow concentric muscle strength as the badminton players, although the badminton players still had a higher isometric rate of force development and muscle strength during fast (240° · s^?1) quadriceps contractions. Large volumes of concurrent endurance training could have attenuated the long-term development of maximal muscle strength in the badminton players. The badminton players had a higher contractile rate of force development than the reference group before and after resistance training. Greater explosive muscle strength in the badminton players might be a physiological adaptation to their badminton training.     

Effect of team rank and player classification on activity profiles of elite wheelchair rugby players

The aim of the current study was to establish which indicators of mobility are associated with successful wheelchair rugby performance and determine whether these indicators differed across classification. Data were collected from 11 international teams during 30 matches (353 match observations) using a radio-frequency-based, indoor tracking system across two tournaments. Players (n = 111) were first grouped by team rank as determined by their International Wheelchair Rugby Federation (IWRF) world ranking (LOW, MID, HIGH) and then into one of four groups based on their IWRF classification: Group I (0.5), Group II (1.0–1.5), Group III (2.0–2.5) and Group IV (3.0–3.5). The volume of activity (relative distance and mean speed), peak speed and time spent within classification-specific arbitrary speed zones were calculated for each individual. Although no differences were identified in the volume of activity, playing time was significantly reduced in LOW (34:51 ± 8:35) compared to MID (48:54 ± 0:51) and HIGH (45:38 ± 9:53), which was further supported by the greater number of substitutions performed by LOW. HIGH achieved greater peak speeds (3.55 ± 0.40 m · sˉ¹) than LOW (3.27 ± 0.42 m · sˉ¹) and MID (3.45 ± 0.41 m · sˉ¹). Peak speed was further shown to be classification-dependent (P ≤ 0.005), whereby HIGH Groups III and IV players achieved greater peak speeds than LOW and MID. The time spent performing high-intensity activities was also greater in HIGH compared to LOW and MID, whilst further influenced by classification (P ≤ 0.0005). To conclude, peak speed and the ability to perform a greater number of high-intensity activities were associated with successful performance in wheelchair rugby.     

Bar velocities capable of optimising the muscle power in strength-power exercises

This study aimed at testing whether there are mean propulsive velocities (MPVs) capable of maximising the mean propulsive power (MPP) during the execution of bench press (BP), bench throw (BT), half squat (HS) and jump squat (JS). Additionally, we assessed the differences in MPP/MPV between ballistic and traditional exercises. Seventeen male rugby sevens players performed MPP tests in BP, BT, HS and JS and maximum isometric force (MIF) tests in HS and BP. The JS presented higher MPP (977.4 ± 156.2 W) than the HS (897.9 ± 157.7 W) (P < 0.05); the BP (743.4 ± 100.1 W) presented higher MPP than the BT (697.8 ± 70.4 W) (P < 0.05). Ballistic exercises presented higher optimum MPV (JS = 1.02 ± 0.07 m·s^?1; BT = 1.67 ± 0.15 m·s^?1) than traditional exercises (HS = 0.93 ± 0.08 m·s^?1; BP = 1.40 ± 0.13 m·s^?1) (P < 0.05). The optimum MPP in the JS, BT, HS and BP occurred at 28.2 ± 5.79, 23.3 ± 4.24, 32.4 ± 9.46 and 27.7 ± 5.33% of the MIF, respectively. The coefficient of variation (CV) of MPV at optimum MPP ranged from 7.4% to 9.7%, while the CV of %MIF ranged from 18.2% to 29.2%. The MPV is a more precise indicator of the optimum loads than the percentages of MIF due to its low inter-subject variability as expressed by CV. Therefore, MPV can be used to determine the optimum power load in the four investigated exercises.     

Reliability and validity of two tests of soccer skill

Abstract

Twenty-four players from the 1st/2nd (elite) and 24 players from the 3rd/4th (non-elite) university football teams were recruited to evaluate the Loughborough Soccer Passing Test (LSPT) and Loughborough Soccer Shooting Test (LSST) as tools to assess soccer skill. The LSPT requires players to complete 16 passes as quickly as possible. The LSST requires players to pass, control, and shoot the ball to targets on a full-sized goal. Participants completed two main trials each separated by at least one day. During both trials, the participants were given practice efforts before recording the mean of the next two (LSPT) or 10 (LSST) attempts as the performance score. For the LSPT, the mean time taken, added penalty time, and overall performance time were less in the elite players (elite: 43.6 s, s = 3.8; non-elite: 52.5 s, s = 7.4; P = 0.0001). For the LSST, there was no difference in the mean points scored per shot between groups (elite: 1.34, s = 0.46; non-elite: 1.28, s = 0.53). However, the elite players had higher mean shot speed (elite: 80 km · h^?1, s = 4.5; non-elite: 74 km · h^?1, s = 4.2; P < 0.0001) and performed each shot sequence faster (elite: 7.87 s, s = 0.29; non-elite: 8.07 s, s = 0.35; P = 0.037) than the non-elite players. Performance on both tests was more repeatable in elite players. In conclusion, the LSPT and LSST are valid and reliable protocols to assess differences in soccer skill performance.     

Movement velocity as a measure of exercise intensity in three lower limb exercises

The purpose of this study was to investigate the relationship between movement velocity and relative load in three lower limbs exercises commonly used to develop strength: leg press, full squat and half squat. The percentage of one repetition maximum (%1RM) has typically been used as the main parameter to control resistance training; however, more recent research has proposed movement velocity as an alternative. Fifteen participants performed a load progression with a range of loads until they reached their 1RM. Maximum instantaneous velocity (V_max) and mean propulsive velocity (MPV) of the knee extension phase of each exercise were assessed. For all exercises, a strong relationship between V_max and the %1RM was found: leg press (r²_adj = 0.96; 95% CI for slope is [?0.0244, ?0.0258], P < 0.0001), full squat (r²_adj = 0.94; 95% CI for slope is [?0.0144, ?0.0139], P < 0.0001) and half squat (r²_adj = 0.97; 95% CI for slope is [?0.0135, ?0.00143], P < 0.0001); for MPV, leg press (r²_adj = 0.96; 95% CI for slope is [?0.0169, ?0.0175], P < 0.0001, full squat (r²_adj = 0.95; 95% CI for slope is [?0.0136, ?0.0128], P < 0.0001) and half squat (r²_adj = 0.96; 95% CI for slope is [?0.0116, 0.0124], P < 0.0001). The 1RM was attained with a MPV and V_max of 0.21 ± 0.06 m s^?1 and 0.63 ± 0.15 m s^?1, 0.29 ± 0.05 m s^?1 and 0.89 ± 0.17 m s^?1, 0.33 ± 0.05 m s^?1 and 0.95 ± 0.13 m s^?1 for leg press, full squat and half squat, respectively. Results indicate that it is possible to determine an exercise-specific %1RM by measuring movement velocity for that exercise.     

Peak oxygen uptake measured during a perceptually-regulated exercise test is reliable in community-based manual wheelchair users

This study compares test-retest reliability and peak exercise responses from ramp-incremented (RAMP) and maximal perceptually-regulated (PRET_max) exercise tests during arm crank exercise in individuals reliant on manual wheelchair propulsion (MWP). Ten untrained participants completed four trials over 2-weeks (two RAMP (0–40 W + 5–10 W · min^?1) trials and two PRET_max. PRET_max consisted of five, 2-min stages performed at Ratings of Perceived Exertion (RPE) 11, 13, 15, 17 and 20). Participants freely changed the power output to match the required RPE. Gas exchange variables, heart rate, power output, RPE and affect were determined throughout trials. The V?O_2peak from RAMP (14.8 ± 5.5 ml · kg^?1 · min^?1) and PRET_max (13.9 ± 5.2 ml · kg^?1 · min^?1) trials were not different (P = 0.08). Measurement error was 1.7 and 2.2 ml · kg^?1 · min^?1 and coefficient of variation 5.9% and 8.1% for measuring V?O_2peak from RAMP and PRET_max, respectively. Affect was more positive at RPE 13 (P = 0.02), 15 (P = 0.01) and 17 (P = 0.01) during PRET_max. Findings suggest that PRET_max can be used to measure V?O_2peak in participants reliant on MWP and leads to a more positive affective response compared to RAMP.     

Early changes in Achilles tendon behaviour in vivo following downhill backwards walking

Downhill backwards walking causes repeated, cyclical loading of the muscle–tendon unit. The effect this type of repeated loading has on the mechanical behaviour of the Achilles tendon is presently unknown. This study aimed to investigate the biomechanical response of the Achilles tendon aponeurosis complex following a downhill backwards walking protocol. Twenty active males (age: 22.3 ± 3.0 years; mass: 74.7 ± 5.6 kg; height: 1.8 ± 0.7 m) performed 60 min of downhill (8.5°), backwards walking on a treadmill at ?0.67 m · s^?1. Data were collected before, immediately post, and 24-, 48- and 168-h post-downhill backwards walking. Achilles tendon aponeurosis elongation, strain and stiffness were measured using ultrasonography. Muscle force decreased immediately post-downhill backward walking (P = 0.019). There were increases in Achilles tendon aponeurosis stiffness at 24-h post-downhill backward walking (307 ± 179.6 N · mm^?1, P = 0.004), and decreases in Achilles tendon aponeurosis strain during maximum voluntary contraction at 24 (3.8 ± 1.7%, P = 0.008) and 48 h (3.9 ± 1.8%, P = 0.002) post. Repeated cyclical loading of downhill backwards walking affects the behaviour of the muscle–tendon unit, most likely by altering muscle compliance, and these changes result in tendon stiffness increases.     

The physiological cost of velocity coupling during tennis groundstrokes

Abstract

Velocity coupling denotes a perceptual motor behaviour known to occur during coincidence timing tasks. Individuals have been shown to increase their effector limb speed with increases in stimulus speed during interceptive tasks. However, little is known about the physiological effects of velocity coupling. The aim of this study was to determine the physiological cost of velocity coupling during tennis groundstrokes. Eight male and eight female competitive tennis players volunteered to perform three 4-min bouts of continuous groundstrokes against balls projected from a tennis ball machine at speeds of 18, 22, and 27 m · s^?1 (65, 79, and 97 km · h^?1) and a frequency of 14 balls per minute, the order of which was counterbalanced. Breath-by-breath pulmonary gas exchange, heart rate, locomotion time, and limb acceleration were measured throughout each of the 4-min bouts. Capillary blood samples (for blood lactate analysis), rating of perceived exertion, and difficulty rating were taken at the end of each bout. Increasing ball speed did not influence the locomotion time between groundstrokes but did result in a bilateral increase in both the mean upper- and lower-limb acceleration (all P < 0.05). Velocity coupling behaviour increased oxygen uptake, blood lactate concentration, heart rate, rating of perceived exertion, and perceived task difficulty (all P < 0.05). It would appear, therefore, that velocity coupling influenced tennis groundstroke behaviour and indirectly modified the concurrent cardiopulmonary and metabolic responses.     

Effect of different inter-repetition rest intervals across four load intensities on velocity loss and blood lactate concentration during full squat exercise

ABSTRACT

This study aimed to analyze the acute effect of inter-repetition rest (IRR) intervals on mechanical and metabolic response during four resistance exercise protocols (REPs). Thirty resistance-trained men were randomly assigned to: continuous repetitions (CR), 10 s (IRR10) or 20 s (IRR20) inter-repetition rest. The REPs consisted of 3 sets of 6, 5, 4 and 3 repetitions against 60, 70, 75 and 80% 1RM, respectively, in the full squat exercise. Muscle fatigue was assessed using: percentage of velocity loss over three sets, percentage of velocity loss against the ~1 m·s^?1 load (V1 m·s^?1), and loss of countermovement jump (CMJ) height pre-post exercise. Blood lactate was measured before and after exercise. The percentage of velocity loss over three sets and lactate concentration were significantly lower (P < 0.05) for IRR groups compared to CR in all REPs. The CR group showed a significantly higher (P < 0.05) velocity loss against V1 m·s^?1 load and loss of CMJ height pre-post exercise than IRR groups in REP against 60% 1RM. In conclusion, both IRR groups produced a significant lower degree of fatigue compared to CR group. However, no significant differences were found in any measured variables between IRR configurations.