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Validity, Reliability and Sensitivity of Measures of Sporting Performance
Abstract
Performance testing is one of the most common and important measures used in sports science and physiology. Performance tests allow for a controlled simulation of sports and exercise performance for research or applied science purposes. There are three factors that contribute to a good performance test: (i) validity; (ii) reliability; and (iii) sensitivity. A valid protocol is one that resembles the performance that is being simulated as closely as possible. When investigating race-type events, the two most common protocols are time to exhaustion and time trials. Time trials have greater validity than time to exhaustion because they provide a good physiological simulation of actual performance and correlate with actual performance. Sports such as soccer are more difficult to simulate. While shuttle-running protocols such as the Loughborough Intermittent Shuttle Test may simulate physiology of soccer using time to exhaustion or distance covered, it is not a valid measure of soccer performance. There is a need to include measures of skill in such protocols. Reliability is the variation of a protocol. Research has shown that time-to-exhaustion protocols have a coefficient of variation (CV) of >10%, whereas time trials are more reliable as they have been shown to have a CV of <5%. A sensitive protocol is one that is able to detect small, but important, changes in performance. The difference between finishing first and second in a sporting event is <1%. Therefore, it is important to be able to detect small changes with performance protocols. A quantitative value of sensitivity may be accomplished through the signal : noise ratio, where the signal is the percentage improvement in performance and the noise is the CV.
... Reliability refers to an instrument's ability to produce consistent measures across multiple time points, thus ensuring change in score is attributed to changes in performance as opposed to instrument errors [23,24]. Validity can be broken into three categories; logical, criterion, and construct [25]. For this review, only construct validity has been reported, i.e. an instrument's ability to correctly diagnose concussed and non-concussed populations. ...
... For this review, only construct validity has been reported, i.e. an instrument's ability to correctly diagnose concussed and non-concussed populations. The higher the sensitivity and specificity of an instrument, the better its ability to classify those with and those without concussion [25]. Feasibility is also vital to consider when selecting a test, the time, and the resources and expertise required as these will influence which tests can be administered. ...
... Clinicians should be encouraged to implement dynamic balance or gait-based assessments as a part of a comprehensive and multifaceted concussion assessment approach, due to their higher test-retest reliability than static approaches. As previously mentioned, consistency across trials allows variations in motor strategies to be more easily detected, when a concussion is sustained [25]. Multiple trials, with the average taken, should be completed if performing non-instrumented static assessments [33], with the assessment made by multiple clinicians, in preference to one to minimise noise in the measurement and allow for smaller changes in performance to be detected as real changes [98]. ...
Background
There is an increased risk of subsequent concussion and musculoskeletal injury upon return to play following a sports-related concussion. Whilst there are numerous assessments available for clinicians for diagnosis and during return to play following concussion, many may lack the ability to detect these subclinical changes in function. Currently, there is no consensus or collated sources on the reliability, validity and feasibility of these assessments, which makes it difficult for clinicians and practitioners to select the most appropriate assessment for their needs.
Objectives
This systematic review aims to (1) consolidate the reliability and validity of motor function assessments across the time course of concussion management and (2) summarise their feasibility for clinicians and other end-users.
Methods
A systematic search of five databases was conducted. Eligible studies were: (1) original research; (2) full-text English language; (3) peer-reviewed with level III evidence or higher; (4) assessed the validity of lower-limb motor assessments used to diagnose or determine readiness for athletes or military personnel who had sustained a concussion or; (5) assessed the test-retest reliability of lower-limb motor assessments used for concussion management amongst healthy athletes. Acceptable lower-limb motor assessments were dichotomised into instrumented and non-instrumented and then classified into static (stable around a fixed point), dynamic (movement around a fixed point), gait, and other categories. Each study was assessed using the COSMIN checklist to establish methodological and measurement quality.
Results
A total of 1270 records were identified, with 637 duplicates removed. Titles and abstracts of 633 records were analysed, with 158 being retained for full-text review. A total of 67 records were included in this review; 37 records assessed reliability, and 35 records assessed the validity of lower-limb motor assessments. There were 42 different assessments included in the review, with 43% being non-instrumented, subjective assessments. Consistent evidence supported the use of instrumented assessments over non-instrumented, with gait-based assessments demonstrating sufficient reliability and validity compared to static or dynamic assessments.
Conclusion
These findings suggest that instrumented, gait-based assessments should be prioritised over static or dynamic balance assessments. The use of laboratory equipment (i.e. 3D motion capture, pressure sensitive walkways) on average exhibited sufficient reliability and validity, yet demonstrate poor feasibility. Further high-quality studies evaluating the reliability and validity of more readily available devices (i.e. inertial measurement units) are needed to fill the gap in current concussion management protocols. Practitioners can use this resource to understand the accuracy and precision of the assessments they have at their disposal to make informed decisions regarding the management of concussion.
Trail Registration: This systematic review was registered on PROSPERO (reg no. CRD42021256298).
... Furthermore, in general, for performance measurements, it is important for subjects to be familiarized with the task to be completed. And although not all tests might benefit from such a familiarization (Currell & Jeukendrup, 2008), it could still be a key factor for certain types of populations and measurements. The results of this first study further confirm this statement for the measurements that were tested: the reliability of all tests increased by the inclusion of a familiarization session. ...
... In the context of this paper, reliability refers to stability or test-retest reliability, which is the variability of a test over time (Baumgartner, 1989). Furthermore, determining the sensitivity of a test tells us if it is able to detect meaningful and small changes between measurements (Currell & Jeukendrup, 2008). ...
... Physical performance tests are commonly used in the medical and exercise science environment. They allow different aspects of the physical and sporting state of a person to be measured in a controlled and scientific manner (Currell & Jeukendrup, 2008). For this, depending on the purpose and intended use, a wide range of tests are available. ...
In the scientific community, a constant effort is made to better understand how the human body works and adapts to different circumstances. And particularly exercise physiology aims at clarifying how the body responds to physical activity and the mechanisms that cause training adaptations. Similarly, over the last more than 50 years, since the beginning of manned space exploration, space scientists have put a great amount of effort into understanding the effects of microgravity on the human body. Interestingly, at the centre of these two research areas, although with apparently different populations, the role of exercise and physical activity is a main topic. This intersection point is the basis for this dissertation. Therefore, the purpose of the present thesis was to explore the different physiological effects, specifically those in the neuromuscular and cardiorespiratory systems, that different intensities of activity—ranging from full inactivity at bed rest (BR) to high levels of activity with high-intensity interval training (HIIT)—exert on the human body. To achieve this, three research projects were conducted. The first study represented the statistical basis to establish the overall reliability and sensitivity of some of the strength and power tests that would be used in the subsequent two studies, and the effect that time plays between testing sessions of these measurements. The results showed that over the course of the 9 weeks, most measurements, but not all, were sensitive and reliable. With more consistent results achieved using the average of results rather than the best result per session. From an applied perspective, these findings have practical applications in increasing confidence in the results of the tests, providing valuable data for sample size calculations, estimating error, and determining if the results found from an intervention are due to error or an actual effect. The second project provided a starting point in the continuum of activity with the deconditioning of the human body. The aim of this study was to assess changes in the participants’ cardiovascular and neuromuscular performance before and after bed rest, and the effect of artificial gravity (AG) as a countermeasure. The results showed that participants in all groups, including those exposed to AG, suffered from severe deconditioning. Nevertheless, AG was partially able to mitigate the physiological consequences caused by BR. Therefore, we concluded that AG would have to be coupled with other forms of exercise to be considered an integral countermeasure for the deconditioning of the human body under BR and microgravity conditions. Finally, the third study contributed key data on the other end of the activity continuum. Its goal was to evaluate whether a jump HIIT could improve aerobic capacity and neuromuscular performance in a recreationally active population in comparison to a running HIIT. The results exhibited that despite identical programming in both HIIT intervention groups (e.g., training frequency, number of series, and work/rest durations), each exercise modality produced different adaptations: the jump training increased leg strength and the running group aerobic capacity. In the jumping group, there was also an important difference in the perceived difficulty of the training sessions, depending on the amount of time between consecutive jumps. With this in mind, it is clear that not only the choice of exercise but also subtle differences in how an exercise is performed can profoundly affect the training adaptations that one attains. All in all, these findings underline the importance of choosing the appropriate exercise type and modality, according to the adaptations that are desired to be obtained. From the findings of this dissertation, it is clear that insights from BR studies go beyond its application to the protection of astronauts in space. This approach is a great tool to further investigate and understand how the human body deconditions, adapts, and rehabilitates. The combined results of the presented BR and HIIT studies, along with related literature, suggest that to prevent deconditioning or produce adaptations in the neuromuscular system, fast and powerful exercises that produce high-strain rates, are essential. And that the cardiorespiratory system appears to be quite responsive to exercise stimulus, even under complete inactivity, provided that the right intensity is achieved.
... 1 Testing allows athletes, coaches, and sport scientists to objectively assess the effects of training interventions, track progress, and identify athletic potential. 2 Quantifying XC skiing performance in the field remains a challenge because skiing velocity on snow and roller skis can fluctuate between sessions on the same track due to the variations in terrain topography and the ever-changing friction resistances influenced by changing snow conditions, pavement surface, and temperatures. Therefore, accurate real-time information on power output is currently lacking to complement the intensity feedback of the physiological responses available during skiing. ...
... 12,13 Test reliability depends on many factors, including measurement error, test protocol, exercise mode, standardization, equipment, athlete's performance level, motivation, and day-to-day biological variation. 2,13 Despite the extensive use of performance testing in XC skiing, reports on the test-retest reliability of ski-specific test protocols to assess aerobic, sprint or neuromuscular capacity are limited. ...
Purpose
Laboratory tests are commonly performed by cross‐country (XC) skiers due to the challenges of obtaining reliable performance indicators on snow. However, only a few studies have reported reliability data for ski‐specific test protocols. Therefore, this study examined the test–retest reliability of ski‐specific aerobic, sprint, and neuromuscular performance tests.
Methods
Thirty‐nine highly trained XC skiers (26 men and 13 women, age: 22 ± 4 years, V̇O2max: 70.1 ± 4.5 and 58.8 ± 4.4 mL·kg⁻¹·min⁻¹, respectively) performed two test trials within 6 days of a diagonal V̇O2max test, n = 27; skating graded exercise test to assess the second lactate threshold (LT2), n = 27; 24‐min double poling time trial (24‐min DP, n = 25), double poling sprint test (SprintDP1, n = 27), and 1‐min self‐paced skating sprint test (Sprint1‐min, n = 26) using roller skis on a treadmill, and an upper‐body strength test (UB‐ST, n = 27) to assess peak power (Ppeak) with light, medium, and heavy loads. For each test, the coefficient of variation (CV), intraclass correlation coefficient (ICC), and minimal detectable change (MDC) were calculated.
Results
V̇O2max demonstrated good‐to‐excellent reliability (CV = 1.4%; ICC = 0.99; MDC = 112 mL·min⁻¹), whereas moderate‐to‐excellent reliability was found for LT2 (CV = 3.1%; ICC = 0.95). Performance during 24‐min DP, SprintDP1, and Sprint1‐min showed good‐to‐excellent reliability (CV = 1.0%–2.3%; ICC = 0.96–0.99). Absolute reliability for UB‐ST Ppeak was poor (CV = 4.9%–7.8%), while relative reliability was excellent (ICC = 0.93–0.97) across the loads.
Conclusion
In highly trained XC skiers, sport‐specific aerobic and sprint performance tests demonstrated high test–retest reliability, while neuromuscular performance for the upper body was less reliable. Using the presented protocols, practitioners can assess within‐ and between‐season changes in relevant performance indicators.
... This finding suggests that the higher external load (faster speed) at 25˚C compensates for the effects of more significant perceptual responses at 35˚C in inducing neuromuscular fatigue. endurance exercise, in which the individuals adjust running speed to choose the best strategy to complete a predetermined distance as fast as possible [29][30][31]. In this regard, Périard et al. [32] reported that the loss of force production following self-paced cycling exercise in the heat was not exacerbated compared to the loss observed under temperate conditions. ...
Environmental heat stress impairs endurance performance by enhancing exercise-induced physiological and perceptual responses. However, the time course of these responses during self-paced running, particularly when comparing hot and temperate conditions, still needs further clarification. Moreover, monitoring fatigue induced by exercise is paramount to prescribing training and recovery adequately, but investigations on the effects of a hot environment on post-exercise neuromuscular fatigue are scarce. This study compared the time course of physiological and perceptual responses during a 10 km self-paced treadmill run (as fast as possible) between temperate (25°C) and hot (35°C) conditions. We also investigated the changes in countermovement jump (CMJ) performance following exercise in these two ambient temperatures. Thirteen recreational long-distance runners (11 men and 2 women), inhabitants of a tropical region, completed the two experimental trials in a randomized order. Compared to 25°C, participants had transiently higher body core temperature (TCORE) and consistently greater perceived exertion while running at 35°C (p < 0.05). These changes were associated with a slower pace, evidenced by an additional 14 ± 5 min (mean ± SD) to complete the 10 km at 35°C than at 25°C (p < 0.05). Before, immediately after, and 1 h after the self-paced run, the participants performed CMJs to evaluate lower limb neuromuscular fatigue. CMJ height was reduced by 7.0% (2.3 ± 2.4 cm) at 1 h after the race (p < 0.05) compared to pre-exercise values; environmental conditions did not influence this reduction. In conclusion, despite the reduced endurance performance, higher perceived exertion, and transiently augmented TCORE caused by environmental heat stress, post-exercise neuromuscular fatigue is similar between temperate and hot conditions. This finding suggests that the higher external load (faster speed) at 25°C compensates for the effects of more significant perceptual responses at 35°C in inducing neuromuscular fatigue.
... This finding suggests that the higher external load (faster speed) at 25˚C compensates for the effects of more significant perceptual responses at 35˚C in inducing neuromuscular fatigue. endurance exercise, in which the individuals adjust running speed to choose the best strategy to complete a predetermined distance as fast as possible [29][30][31]. In this regard, Périard et al. [32] reported that the loss of force production following self-paced cycling exercise in the heat was not exacerbated compared to the loss observed under temperate conditions. ...
... The measurement of punch force, as with any performance measure, must be ecologically valid and reliable for it to be effective, and must also be sensitive enough to detect changes in performance [10][11][12][13]. Test-retest reliability concerns the reproducibility of the observed value when the measurement is repeated [10,12,13]. ...
An ecologically valid, reliable and sensitive method of quantifying punch force variables would be useful for coaches and practitioners monitoring combat-specific performance. The present study utilised a vertically mounted force plate to quantify the peak punch force and rate of force development (RFD) of amateur boxers. Ten male senior elite amateur boxers performed maximal jab, cross, and hook punches across two separate days. The force plate showed excellent within-day and good-to-excellent between-day reliability for peak punch impact force and RFD (ICC 0.89-0.99). The CV% for all punch force variables were similar on day 1 (3-9%) and day 2 (4-10%). Standard error of measurement (SEM) and smallest worthwhile changes (SWC) revealed the force plate can detect small-to-moderate changes in punch performance. The greatest impact forces and RFD were found in the rear hook (2624 ± 581 N, 296448 ± 101823 N.s-1), followed by the lead hook (2524 ± 532 N, 256813 ± 81735 N.s-1), cross 2425 ± 545 N, 193004 ± 62671 N.s-1) and jab (1645 ± 537 N, 116675 ± 41577 N.s-1). The vertically mounted force plate is a reliable and sensitive test of punch performance, thus may be useful in determining the efficacy of training interventions.
... Com essa finalidade, a literatura sugere a utilização de listas de verificação como instrumento de avaliação [8][9][10][11] para uma melhor análise dos componentes principais do movimento e adequado julgamento 5 . Entretanto, a lista de verificação deve ser objetiva, ter validade, ser de fácil utilização e atender a exigências de confiabilidade 9,11,12 A confiabilidade refere-se à condição de uma avalição ou uma medida apresentar resultados semelhantes em ocasiões diferentes, desde que não haja uma interferência com o objetivo de modificação do desempenho 4,11,13 . Este é um procedimento importante que garantirá que os resultados dos avaliadores são consistente 11,14 . ...
Esse estudo teve por objetivo avaliar o efeito da padronização dos critérios de observação e de avaliação da técnica da braçada do nado crawl na confiabilidade inter e intra avaliadores para uma proposta de lista de observação. Dois professores e dois treinadores de natação competitiva com formação acadêmica diferentes foram responsáveis por avaliar a técnica da braçada do nado crawl de 44 nadadores por meio de vídeo. Cada nadador realizou um percurso de 25m em velocidade confortável tendo seu deslocamento gravado nos planos lateral e frontal, ambos submersos e fora d’água, nos 10 m finais da piscina. No percurso de filmagem os nadadores não realizaram a respiração lateral. Somente o movimento realizado pelo braço direito foi foco de observação dos avaliadores e com base em uma lista de verificação. Após as filmagens os avaliadores participaram de três etapas: na primeira etapa houve uma intervenção para padronização dos critérios de observação e de avaliação. Na segunda etapa testou-se a concordância inter-avaliadores e, na terceira, a concordância intra-avaliador. Na segunda etapa do estudo a concordância variou de pequeno a baixa (k=0,08 e k=0,38). Na terceira etapa alguns avaliadores apresentaram concordância pobre e baixa (k=-0,13 e k=0,35), enquanto outros apresentaram concordância entre razoável e praticamente perfeita (k=0,64 e k=0,87). A partir dos resultados apresentados concluiu-se que a proposta de intervenção não surtiu o efeito desejado de padronização dos critérios de observação e avaliação entre os avaliadores
... Reliability refers to the condition for a rating or a measurement to present similar results on different occasions, as long as there is no interference with the objective of changing performance 4,11,13 . This is an important procedure that will ensure that the raters' results are consistent 11,14 . ...
This study aimed to assess the effect of standardizing observation and rating criteria for the front crawl stroke technique on inter- and intra-rater reliability in order to propose an observation list. Two teachers and two competitive swimming coaches with different academic backgrounds were responsible for evaluating the front crawl stroke technique of 44 swimmers using video. Each swimmer completed a 25m course at a comfortable speed, having their displacement recorded in the lateral and frontal planes, both submerged and out of water, in the final 10 m of the pool. Throughout the recording, the swimmers did not breath laterally. Only the movement performed by the right arm was the raters’ focus of observation and was based on a checklist. After the shooting, the raters participated in three stages: in the first stage, there was an intervention to standardize the observation and rating criteria; inter-rater agreement was tested in the second stage, while intra-rater agreement was obtained in the third. In the second stage of the study, the agreement ranged from small to low (k=0.08 and k=0.38). In the third stage, some raters showed poor and low agreement (k=-0.13 and k=0.35), while others showed agreement between reasonable and virtually perfect (k=0.64 and k=0.87). From the results presented, it was concluded that the intervention proposal did not have the desired effect of standardizing the observation and rating criteria among the raters.
Keywords:
Swimming; Sport; Rating and Pedagogy
To our knowledge, no study has investigated the reliability of the time to exhaustion (TTE) test during constant-load trials in Olympic distance cross-country mountain bike (XCO-MTB) athletes. Thus, the aim was to analyze the reliability of the TTE test at intensities above peak oxygen uptake (VO2peak) in trained XCO-MTB athletes. Fifteen male XCO-MTB athletes (mean ± SD: age 31.5 ± 6.6 years, stature 174.0 ± 5.4 cm, body mass 67.2 ± 5.1 kg, VO2peak 64.5 ± 4.7 mL·kg-1·min-1) completed 2 TTE tests on the cycle ergometer with 4 different intensities above the maximal work rate in the incremental test (Wmax) (105%, 120%, 130%, and 140% of Wmax). There was moderate reliability between TTE tests at 105% (intraclass correlation coefficient (ICC) = 0.81, p ≤ 0.001; coefficient of variation (CV) = 9.1%; standard error of measurement (SEM) = 18.3%), and 120% (ICC = 0.88, p ≤ 0.001; CV = 6.6%; SEM = 9.3%) Wmax. For intensities of 130% (ICC = 0.53, p = 0.018; CV = 9.2%; SEM = 15.8%) and 140% (ICC = 0.56, p = 0.012; CV = 12.2%; SEM = 13.5%) Wmax, the reliability results proved to be questionable. In addition, no significant differences were found between the 2 TTE tests in all intensities (p > 0.05). Caution should be taken when assessing TTE above VO2peak or when using it as a performance indicator, given its moderate to questionable reliability.
Kyles, A, Oliver, JL, Cahill, MJ, Lloyd, RS, and Pedley, J. Linear and change of direction repeated sprint ability tests: a systematic review. J Strength Cond Res 37(8): 1703-1717, 2023-The ability to repeatedly sprint is important in many sports, but there is no established protocol for measuring repeated sprint ability (RSA). The purpose of this review was to identify overground RSA protocols previously reported in the literature and to recommend standardized protocols. A systematic review of the literature was used to identify studies that have used an RSA test, with data describing protocol design extracted. One hundred eight studies were included in the review, across which 47 unique protocols were identified. Eighteen protocols included at least one change of direction (COD), and this increased mean sprint time compared with linear RSA tests (7.26 ± 1.84 vs. 4.48 ± 1.02 seconds). There was considerable variability across protocols regarding sprint distance (20-40 m), sprint repetitions (3-15), recovery duration (10-60 seconds), recovery type (active vs. passive), and work-to-rest ratio (≤1:1.4-19.2). Separate protocols are needed for linear and COD tests, and these should reflect the brief nature of intense periods of competition and stress the ability to recover. Based on data across studies for protocol design and to ensure a demanding work-to-rest ratio, it is suggested that a linear RSA should comprise 6 × 30 m sprints separated by 15 seconds of active recovery. To provide some parity to linear tests, to keep work duration brief and to maintain a demanding work-to-rest ratio, a COD RSA should comprise 6 × 30 m shuttle sprints (15 + 15 m), providing one change of direction (180° COD), and maintaining a 15-second active recovery.
Purpose: The purpose of this study was to examine the influence of three different high-intensity interval training (HIT) regimens on endurance performance in highly trained endurance athletes. Methods: Before, and after 2 and 4 wk of training, 38 cyclists and triathletes (mean +/- SD; age = 25 +/- 6 yr; mass = 75 +/- 7 kg; (V)over dot O-2peak = 64.5 +/- 5.2 mL.kg(-1).min(-1)) performed: 1) a progressive cycle test to measure peak oxygen consumption ((V)over dotO(2peak)) and peak aerobic power output (PPO), 2) a time to exhaustion test (T-max) at their (V)over dotO(2peak) power output (P-max), as well as 3) a 40-kin time-trial (TT40). Subjects were matched and assigned to one of four training groups (G(1), N = 8, 8 X 60% T-max P-max, 1:2 work:recovery ratio; G(2), N = 9, 8 X 60% T-max at P-max, recovery at 65% HRmax; G(3), N = 10, 12 X 30 s at 175% PPO, 4.5-min recovery; G(CON), N = 11). In addition to G(1) G(2), and G(3) performing HIT twice per week, all athletes maintained their regular low-intensity training throughout the experimental period. Results: All HIT groups improved TT40 performance (+4.4 to +5.8%) and PPO (+3.0 to +6.2%) significantly more than G(CON) (-0.9 to + 1.1 %; P < 0.05). Furthermore, G(1) (+5.4%) and G(2) (+8.1%) improved their (V)over dot O-2peak significantly more than G(CON) (+ 1.0%; P < 0.05). Conclusion: The present study has shown that when HIT incorporates P-max as the interval intensity and 60% of T-max as the interval duration, already highly trained cyclists can significantly improve their 40-km time trial performance. Moreover, the present data confirm prior research, in that repeated supramaximal HIT can significantly improve 40-km time trial performance.
The purpose of this study was to assess the reproducibility of running time to exhaustion (Tlim) at maximal aerobic speed (MAS: the minimum speed that elicits VO2max), on eight subelite male long distance runners (29 +/- 3-yr-old; VO2max = 69.5 +/- 4.2 ml.kg(-1).min(-1); MAS = 21.25 +/- 1.1 km.h(-1)). No significant differences were observed between Tlim measured on a treadmill at a 1-wk interval (404 +/- 101 s vs 402 +/- 113 s; r = 0.864); however, observation of individual data indicates a wide within-subjects variability (CV = 25%). In a small and homogenous sample of runners studied, exercise time to exhaustion at MAS was not related to VO2max (r = 0.138), MAS (r = 0.241), running economy (mlO(2).kg(-1).min(-1) at 16 km.h(-1)) (r = 0.024), or running performance achieved for 3000 m (km.h(-1)) (r = 0.667). However, Tlim at MAS was significantly related to the lactate threshold determined by the distinctive acceleration point detected in the lactate curve around 3-5 mmol.l(-1) expresses in %VO2max (r = 0.745) and to the speed over a 21.1-km race (km.h(-1)) (r = 0.719). These data demonstrate that running time to exhaustion at MAS in subelite male long distance runners is related to long distance performance and lactate threshold but not to VO2max or MAS.
Prozone® is a new computerised video system that allows the tracking of many individuals performing a sporting activity. The aim of this study was to validate the Prozone® measurement system when measuring displacement velocities on a football pitch. Six male, recreationally active, subjects participated in the study. The subjects performed a series of runs in a straight line and different directions. The following runs were performed and tracked with the Prozone® system: 60m runs, 50m curved runs (30m straight, 20m angled) at different speeds (7 km/h, 11 km/h, 14 km/h, 19 km/h, and 23 km/h), one maximal sprint of 15m and a 20m sprint with a 90 degree turn (10m straight, 10 m left or right) in different zones of the Old Trafford and Reebook Stadiums.
The subjects performed the 60m and 50m curved runs at a predetermined pace with an audio velocity control. For the short distances, the subjects were asked to run as fast as possible. For all runs, timing gates data were compared to tracking data measured with Prozone ®.
The average velocity recorded by the Prozone ® system during the paced runs of 60m and 50m showed an excellent correlation (r = 0.999; Total error 0.05, Limits of agreement 0.12) with the average velocity measured by timing gates. Similar correlation (r = 0.970; Total error 0.23, Limits of agreement 0.85) was recorded during the maximal 15m sprint and during the maximal 20m sprint with right or left turns (r = 0.960; Total error 0.05, Limits of agreement 0.12). The results of this study show that Prozone® represents a valid motion analysis system for analysing movement patterns of footballers on a football pitch.
Purpose:
The purpose of this study was to assess research aimed at measuring performance enhancements that affect success of individual elite athletes in competitive events.
Analysis:
Simulations show that the smallest worthwhile enhancement of performance for an athlete in an international event is 0.7-0.4 of the typical within-athlete random variation in performance between events. Using change in performance in events as the outcome measure in a crossover study, researchers could delimit such enhancements with a sample of 16-65 athletes, or with 65-260 in a fully controlled study. Sample size for a study using a valid laboratory or field test is proportional to the square of the within-athlete variation in performance in the test relative to the event; estimates of these variations are therefore crucial and should be determined by repeated-measures analysis of data from reliability studies for the test and event. Enhancements in test and event may differ when factors that affect performance differ between test and event; overall effects of these factors can be determined with a validity study that combines reliability data for test and event. A test should be used only if it is valid, more reliable than the event, allows estimation of performance enhancement in the event, and if the subjects replicate their usual training and dietary practices for the study; otherwise the event itself provides the only dependable estimate of performance enhancement. Publication of enhancement as a percent change with confidence limits along with an analysis for individual differences will make the study more applicable to athletes. Outcomes can be generalized only to athletes with abilities and practices represented in the study.
Conclusion:
estimates of enhancement of performance in laboratory or field tests in most previous studies may not apply to elite athletes in competitive events.
To examine the variance in time to exhaustion (TE) and oxygen deficit (O2D) in supramaximal exercise, four trained male cyclists repeated rides at an intensity equivalent to 120% V̇O2 max power output. Oyxgen deficit was calculated as the difference between the predicted oxygen consumption and the measured oxygen consumption. Individual coefficients of variation (CV) of 8.6-12.6% for TE and 7.9-12.5% for O2D were reported. No significant differences in TE or O2D were determined across the four tests (p>0.05). It is concluded that the oxygen deficit may be a reliable means of assessing changes in anaerobic capacity in training or metabolic studies designed to improve understanding of glycolytic processes.
A methodology to assess work rate in competitive professional football was designed and validated. The technique required monitoring by observation the intensity and extent of discrete activities during match play and was found to have a measurement error of less than one percent. Performance was observed over 51 games. A complete match typically involved approximately nine hundred separate movement activities per player. The overall distance covered per game was observed to be a function of positional role, the greatest distance covered in outfield players being in mid fielders, the least in centre backs.
The aim of this study was to examine the effects of a carbohydrate-electrolyte drink on specific soccer tests and performance. Twenty-two professional male soccer players volunteered to participate in the study. The players were allocated to two assigned trials ingesting carbohydrate-electrolyte drink (7% carbohydrates, sodium 24 mmol.l-1, chloride 12 mmol.l-1, potassium 3 mmol.l-1) or placebo during a 90 min on-field soccer match. The trials were matched for subjects' age, weight, height and maximal oxygen uptake. Immediately after the match, players completed four soccer-specific skill tests. Blood glucose concentration [mean (SD)] was higher at the end of the match-play in the carbohydrate-electrolyte trial than in the placebo trial (4.4 (0.3) vs. 4.0 (0.3) mmol.l-1, P < 0.05). Subjects in the carbohydrate-electrolyte trial finished the specific dribble test faster in comparison with subjects in the placebo trial (12.9 (0.4) vs. 13.6 (0.5) s, P < 0.05). Ratings of the precision test were higher in the carbohydrate-electrolyte trial as compared to the placebo trial (17.2 (4.8) vs. 15.1 (5.2), P < 0.05) but there were no differences in coordination test and power test results between trials. The main finding of the present study indicates that supplementation with carbohydrate-electrolyte solution improved soccer-specific skill performance and recovery after an on-field soccer match compared with ingestion of placebo. This suggests that soccer players should consume carbohydrate-electrolyte fluid throughout a game to help prevent deterioration in specific skill performance.
Another way of improving time trial performance is by reducing the power demand of riding at a certain velocity. Riding with hands on the brake hoods would improve aerodynamics and increase performance time by ≈5 to 7 minutes and riding with hands on the handlebar drops would increase performance time by 2 to 3 minutes compared with a baseline position (elbows on time trail handle bars). Conversely, riding with a carefully optimised position could decrease performance time by 2 to 2.5 minutes. An aerodynamic frame saved the modelled riders 1:17 to 1:44 min:sec. Furthermore, compared with a conventional wheel set, an aerodynamic wheel set may improve time trial performance time by 60 to 82 seconds. From the analysis in this article it becomes clear that novice cyclists can benefit more from the suggested alterations in position, equipment, nutrition and training compared with elite cyclists. Training seems to be the most important factor, but sometimes large improvements can be made by relatively small changes in body position. More expensive options of performance improvement include altitude training and modifications of equipment (light and aerodynamic bicycle and wheels). Depending on the availability of time and financial resources cyclists have to make decisions about how to achieve their performance improvements. The data presented here may provide a guideline to help make such decisions.