Heart rate monitoring: applications and limitations

High resolution MEMS accelerometers to estimate VO2 and compare running mechanics between highly trained inter-collegiate and untrained runners

BACKGROUND

The purposes of this study were to determine the validity and reliability of high resolution accelerometers (HRA) relative to VO(2) and speed, and compare putative differences in HRA signal between trained (T) and untrained (UT) runners during treadmill locomotion.

METHODOLOGY

Runners performed 2 incremental VO(2max) trials while wearing HRA. RMS of high frequency signal from three axes (VT, ML, AP) and the Euclidean resultant (RES) were compared to VO(2) to determine validity and reliability. Additionally, axial rms relative to speed, and ratio of axial accelerations to RES were compared between T and UT to determine if differences in running mechanics could be identified between the two groups.

PRINCIPAL FINDINGS

Regression of RES was strongly related to VO(2), but T was different than UT (r = 0.96 vs 0.92; p<.001) for walking and running. During walking, only the ratio of ML and AP to RES were different between groups. For running, nearly all acceleration parameters were lower for T than UT, the exception being ratio of VT to RES, which was higher in T than UT. All of these differences during running were despite higher VO(2), O(2) cost, and lower RER in T vs UT, which resulted in no significant difference in energy expenditure between groups.

CONCLUSIONS/SIGNFICANCE

These results indicate that HRA can accurately and reliably estimate VO(2) during treadmill locomotion, but differences exist between T and UT that should be considered when estimating energy expenditure. Differences in running mechanics between T and UT were identified, yet the importance of these differences remains to be determined.

Improved swimming pool achieves higher reproducibility and sensitivity to effect of food components as ergogenic AIDS

A previously developed current swimming pool for mice has been used to evaluate many food components that enhance endurance exercise performance. In this article, to improve reproducibility, reliability and sensitivity of this assay system, we improved the spout part to generate a uniform current and divided the pool into six lanes to avoid physical interference between swimming mice. The stability of the current flow was assessed by measuring the surface current speed and water volume from the spout part. Maximum swimming times of ddY and BALB/c mice were measured to assess the reproducibility of the maximum swimming time. The improvement in sensitivity compared to the original equipment was estimated under three physiological conditions: low carbohydrate diet feeding, low blood hemoglobin level, and carbohydrate supplementation during exercise. The new spout part improved uniformity and quick adjustment of surface current, yielding an increase of workload in a stepwise manner during swimming. Exercise workload was increased in proportion to surface current speed, as evidenced by cadence of kicks and serum lactic acid levels. The improved swimming pool showed higher reproducibility of swimming time until fatigue (p<0.0001). Correspondence between blood hemoglobin concentration and swimming time was improved in the swimming pool. The improved swimming pool yielded higher sensitivity for low carbohydrate diet feeding (p<0.0001) and carbohydrate supplementation during exercise (p<0.01) compared to the original swimming pool. The improvement of the swimming pool achieved higher sensitivity and reproducibility in assessing various diet and food components compared to the original swimming pool.

Relationship between exercise capacity and heart rate variability: supine and in response to an orthostatic stressor

The study investigated whether supine-measured HRV indicators, and/or HRV indicators measured during orthostatic stress are related to conventional measures of exercise and performance ability such as VO(2max). Only two significant correlations (p<0.05) out of 30 tests were found between supine-determined HRV indicators and conventional measures. In contrast, fifteen of the 30 relationships calculated during orthostatic stress were significant. Relationships were at best low to moderate (0.2<|corr|<0.4). As expected, the relationships obtained during orthostatic stress were reversed from that obtained in the supine position. In summary, although HRV indicators are related to cardiovascular fitness, correlations between VO(2max) and these parameters are found only under very specific conditions. HRV parameters explain very little of the variance in VO(2max). In addition, estimating the exercise capacity from HRV indicators requires experience and extreme caution.

Nonlinear modeling and control of human heart rate response during exercise with various work load intensities

The first objective of this paper is to introduce a nonlinear system to model the heart rate (HR) response during and after treadmill walking exercise. The model is a feedback interconnected system that has components to describe the central and peripheral local responses to exercise and their interactions. The parameters of the model were experimentally identified from subjects walking on a treadmill at different speeds. The stability of the obtained nonlinear model was mathematically proven. The modeling results demonstrate that the proposed model can be useful in examining the cardiovascular response to exercise. Based on the nonlinear model, the second objective is to present a computer-controlled treadmill system for the regulation of HR during treadmill exercise. The proposed nonlinear controller consists of feedforward and feedback components. The designed control system was experimentally verified and the results demonstrated that the proposed computer-controlled treadmill system regulated the HR of the experimental subjects according to two different exercising HR profiles, indicating that it can play an important role in the design of exercise protocols for individuals.

A robust control design for heart rate tracking during exercise

In this study, a control design is proposed for the tracking control of heart rate response during treadmill exercise. The controller tracks an exerciser's heart rate to a given heart rate profile, that may represent a prescribed exercise protocol, by varying the speed of the treadmill. A guaranteed cost control approach is adopted in the control design so that the controller guarantees a certain level of performance. The effectiveness of the proposed control design is demonstrated via a simulation study. The controller will be useful in the design of exercise protocols for individuals.

Autonomic control of heart rate during and after exercise : measurements and implications for monitoring training status

Endurance training decreases resting and submaximal heart rate, while maximum heart rate may decrease slightly or remain unchanged after training. The effect of endurance training on various indices of heart rate variability remains inconclusive. This may be due to the use of inconsistent analysis methodologies and different training programmes that make it difficult to compare the results of various studies and thus reach a consensus on the specific training effects on heart rate variability. Heart rate recovery after exercise involves a coordinated interaction of parasympathetic re-activation and sympathetic withdrawal. It has been shown that a delayed heart rate recovery is a strong predictor of mortality. Conversely, endurance-trained athletes have an accelerated heart rate recovery after exercise. Since the autonomic nervous system is interlinked with many other physiological systems, the responsiveness of the autonomic nervous system in maintaining homeostasis may provide useful information about the functional adaptations of the body. This review investigates the potential of using heart rate recovery as a measure of training-induced disturbances in autonomic control, which may provide useful information for training prescription.

Comparison of the Polar S810i monitor and the ECG for the analysis of heart rate variability in the time and frequency domains

The aim of the present study was to compare heart rate variability (HRV) at rest and during exercise using a temporal series obtained with the Polar S810i monitor and a signal from a LYNX(R) signal conditioner (BIO EMG 1000 model) with a channel configured for the acquisition of ECG signals. Fifteen healthy subjects aged 20.9 +/- 1.4 years were analyzed. The subjects remained at rest for 20 min and performed exercise for another 20 min with the workload selected to achieve 60% of submaximal heart rate. RR series were obtained for each individual with a Polar S810i instrument and with an ECG analyzed with a biological signal conditioner. The HRV indices (rMSSD, pNN50, LFnu, HFnu, and LF/HF) were calculated after signal processing and analysis. The unpaired Student t-test and intraclass correlation coefficient were used for data analysis. No statistically significant differences were observed when comparing the values analyzed by means of the two devices for HRV at rest and during exercise. The intraclass correlation coefficient demonstrated satisfactory correlation between the values obtained by the devices at rest (pNN50 = 0.994; rMSSD = 0.995; LFnu = 0.978; HFnu = 0.978; LF/HF = 0.982) and during exercise (pNN50 = 0.869; rMSSD = 0.929; LFnu = 0.973; HFnu = 0.973; LF/HF = 0.942). The calculation of HRV values by means of temporal series obtained from the Polar S810i instrument appears to be as reliable as those obtained by processing the ECG signal captured with a signal conditioner.

Exercise intensity prescription in obese individuals

The main purpose of this study was to evaluate the relationship between different methods proposed by the American College of Sports Medicine (ACSM) to prescribe exercise intensity using heart rate (HR) and oxygen uptake (VO2) in obese individuals. Sixty-eight overweight to severely obese adults were divided into three groups (tertile) based on their BMI. The groups were T1 group (BMI = 30.5 +/- 1.5, n = 23), T2 group (BMI = 34.3 +/- 1.0, n = 23), and T3 group (BMI = 40.2 +/- 3.7, n = 22). All subjects performed a graded exercise test using a ramp protocol on a treadmill. Individual linear regressions between %HR reserve (%HRR) and %VO2 reserve (%VO2R), %HRR and %VO2 peak (%VO2peak), %maximal HR (%HRmax) and %VO2R, and %HRmax and %VO2peak were calculated. When all the subjects were grouped together, the %HRR-%VO2R mean regression was partially related to the line of identity, while the %HRR-%VO2peak, %HRmax-%VO2R, and %HRmax-%VO2peak mean regressions were all significantly different than the line of identity (P < 0.001). The degree of obesity accounted for approximately 15% of the variation for both %HRR-%VO2R and %HRR-%VO2peak mean regressions. The %HRmax-%VO2R and %HRmax-%VO2peak mean regressions were not affected by the degree of obesity but resting HR accounted for 28-37% of the variation. The relationship between the exercise intensity determined by the %HRR-%VO2R and the %HRR-%VO2peak mean regression seems to be influenced by the degree of obesity. The degree of obesity does not affect the relationship between exercise intensity generated by the %HRmax-%VO2R or %HRmax-%VO2peak equations but the resting HR does.

Heart rate in professional musicians

Background

Very few studies have analysed heart rate (HR) with regard to music playing, and the scarce evidence available is controversial. The purpose of this study was to analyse the HR response of professional musicians during their real-work activity.

Methods

Sixty-two voluntary professional musicians (20 women, 42 men), whose ages ranged between 15 and 71 years old, underwent the test while playing their instruments in real life scenarios, i.e. rehearsals, practice and public concerts. The musicians carried Sport Tester PE4000 (Polar^®, Finland) pulsometers to record their HR.

In order to compare data from differently aged subjects we calculated their Maximum Theoretical Heart Rate (MTHR). Later on we found out the MTHR percentages (%MTHR) corresponding to the registered HR of each subject in different situations. The value of the MTHR for every musician was obtained by means of the 220 – age (in years) formula.

Results

Throughout the HR recordings, we have observed that musicians present a heightened HR while playing (in soloists, mean and maximum HR were 72% and 85%MTHR, respectively). Cardiac demand is significantly higher in concerts than in rehearsals while performing the same musical piece. The HR curves corresponding to the same musician playing in repeated concerts (with the same programme) were similar.

Conclusion

The cardiac demand of a professional instrument player is higher than previously described, much greater than what would be expected from a supposedly sedentary activity.

Heart rate in professional musicians

BACKGROUND

Very few studies have analysed heart rate (HR) with regard to music playing, and the scarce evidence available is controversial. The purpose of this study was to analyse the HR response of professional musicians during their real-work activity.

METHODS

Sixty-two voluntary professional musicians (20 women, 42 men), whose ages ranged between 15 and 71 years old, underwent the test while playing their instruments in real life scenarios, i.e. rehearsals, practice and public concerts. The musicians carried Sport Tester PE4000 (Polar(R), Finland) pulsometers to record their HR.In order to compare data from differently aged subjects we calculated their Maximum Theoretical Heart Rate (MTHR). Later on we found out the MTHR percentages (%MTHR) corresponding to the registered HR of each subject in different situations. The value of the MTHR for every musician was obtained by means of the 220 - age (in years) formula.

RESULTS

Throughout the HR recordings, we have observed that musicians present a heightened HR while playing (in soloists, mean and maximum HR were 72% and 85%MTHR, respectively). Cardiac demand is significantly higher in concerts than in rehearsals while performing the same musical piece. The HR curves corresponding to the same musician playing in repeated concerts (with the same programme) were similar.

CONCLUSION

The cardiac demand of a professional instrument player is higher than previously described, much greater than what would be expected from a supposedly sedentary activity.

Quantifying continuous exercise using the ratio of work completed to endurance limit associated with exercise-induced delayed-onset muscle soreness

This study quantified training load of various exercises using a novel method developed by the authors and based on the ratio of work completed: endurance limit, associated with exercise-induced delayed-onset muscle soreness. Exercises were also quantified using the Training Impulse method. 8 runners performed a marathon and a 60-min. run at marathon velocity, and 9 rowers performed two maximal exercises (500 m and 2000 m) on a rowing ergometer. To examine the validity of the two methods, the relationships between the training loads provided by the Training Impulse and the Authors' methods, the direct comparison of the tasks performed, and the usability of the Authors' method components in regular training were assessed. Authors' method was significantly related to Training Impulse method (r = .83, p < .05) and was higher for running (r = .94, p < .05) but none was observed for rowing. In both methods, the marathon run resulted in high training load compared with the other tasks. When compared with the 60-min. run, the training load of the 2000-m row was slightly higher for the Authors' method, but lower for Training Impulse method. In the Authors' method, the delayed-onset muscle soreness component discriminates the marathon from the other tasks whereas the ration of work completed: endurance limit differentiates the 60-min. run from the 2000-m row. The duration component of the Training Impulse method could lead to overestimation of the training load of prolonged exercises compared with high intensity exercise. The relationship between the Training Impulse and the Authors' methods for prolonged exercises, the training load provided for each task, and the components of the Authors' method supported the validity of this new tool to describe exercise-induced fatigue.

Avaliação da reprodutibilidade e validade de questionário de atividade física para gestantes

INTRODUÇÃO: A prática de atividade física tem sido incentivada por vários organismos nacionais e internacionais visando a promoção de saúde. Entretanto não existe consenso acerca da influência e da intensidade ótima de atividade física durante a gestação, possivelmente devido a dificuldades de mensuração e classificação do nível de atividade física através de questionários. Não se identificou qualquer estudo de validação de questionário de atividade física em gestantes no Brasil. O objetivo do presente estudo é analisar a reprodutibilidade e validade concorrente de um questionário de atividades físicas para gestantes. MÉTODOS: Em amostra de 68 gestantes, no segundo trimestre de gestação foi realizada entrevista para aplicação do questionário, que foi repetida com aproximadamente uma semana de intervalo e no puerpério. No período entre as duas primeiras entrevistas, as mulheres utilizaram monitor de freqüência cardíaca (n=38). RESULTADOS: As análises de reprodutibilidade foram adequadas com coeficientes de correlação intraclasse variando de 0,54 a 0,85. A análise das variáveis categóricas, com questões subjetivas e de autopercepção da atividade física, resultou em maior intervalo de coeficiente kappa com valores entre 0,29 e 0,76 entre a aplicação do questionário com uma semana de intervalo, e 0,08 a 0,70 comparado ao puerpério. As análises de validade conduziram a resultado satisfatório quanto à média das diferenças encontrada por intermédio do gráfico de Bland e Altman (1986) entre o questionário e o freqüencímetro. Entretanto, o intervalo da dispersão não se apresentou adequado, visto que variou em mais de sete horas para atividades leves e em quase onze horas por dia para atividades moderadas. As análises do presente estudo parecem assegurar a reprodutibilidade do questionário de atividade física para gestantes. No entanto, com relação à validação, a comparação com os resultados obtidos pelo freqüêncímetro não mostrou graus de concordância adequados.

Cardiorespiratory responses during running and sport-specific exercises in handball players

To determine whether a 4-a-side handball (HB) game is an appropriate aerobic stimulus to reach and potentially enhance maximal oxygen uptake (V O(2)max), and whether heart rate (HR) is a valid index of V O(2) during a handball game. Nine skilled players (21.0+/-2.9 yr) underwent a graded maximal aerobic test (GT) where V O(2)max and HR-V O(2) relationship were determined. V O(2), HR and blood lactate ([La](b)) were recorded during a 2 x 225 s (interspersed with 30s rest) 4-a-side handball game and were compared to those measured during an 480-s running intermittent exercise (IE). Mean V O(2) tended to be higher in handball compared to IE (93.9+/-8.5 vs. 87.6+/-7.4% O(2)max, p=0.06), whereas HR was similar (92.3+/-4.9 vs. 93.9+/-3.9% of the peak of HR, p=0.10). [La](b) was lower for handball than for IE (8.9+/-3.5 vs. 11.6+/-2.1 mmol l(-1), p=0.04). Time spent over 90% of V O(2)max was higher for handball than for IE (336.1+/-139.6s vs. 216.1+/-124.7s; p=0.03). The HR-V O(2) relationship during GT was high (r(2)=0.96, p<0.001) but estimated V O(2) from HR was lower to that measured (p=0.03) in handball, whereas there was no difference in IE. 4-a-side handball game can be used as a specific alternative to IE for enhancing aerobic fitness in handball players. Nevertheless, the accuracy of HR measures for estimating V O(2) during handball is poor.

Heart rate variability as a measure of disease state in irritable bowel syndrome

Heart rate variability (HRV) is a noninvasive measure of sympathovagal balance in the autonomic nervous system (ANS). This review will: (a) consider HRV measurement in irritable bowel syndrome (IBS); (b) discuss the applicability of HRV measurement in IBS by addressing strengths and limitations; and (c) propose future directions in this field of gastrointestinal research and clinical practice. As a strength, analyzing HRV components is a useful method and appears most suitable for detection of changes in ANS sympathovagal balance in both stress and non-stress conditions with good validity and reliability. Also, it is an appropriate measure for ANS in studies with large populations, in both laboratory and clinical settings, and for longitudinal studies because of its noninvasive assets. With regard to limitations of measuring HRV, these are poor standardization, additional human editing, not considering medication or other confounding factors, inconsistent results in gastrointestinal vagal tone study, and different time periods.

Heart rates of high school physical education students during team sports, individual sports, and fitness activities

This study examined how activity type influenced heart rates and time spent in target heart rate zones of high school students participating in physical education classes. Significantly higher average heart rates existed for fitness (142 +/- 24 beats per minute [bpm]) compared to team (118 +/- 24 bpm) or individual (114 +/- 18) activities. Similar results occurred for the percentage of activity time spent within a target heart rate zone (fitness 81.7 +/- 15.9%, individual 68.4 +/- 30.5%, and team 60.6 +/- 30.5%). Boys attained higher heart rates during team activities, while female students had higher rates during individual activities indicating male and female adolescents respond differently to activity types. The highest mean heart rates were observed during fitness activities.

The Respiratory Exchange Ratio is Associated with Fitness Indicators Both in Trained and Untrained Men: A Possible Application for People with Reduced Exercise Tolerance

Background:

The respiratory exchange ratio (RER) indirectly shows the muscle’s oxidative capacity to get energy. Sedentarism, exercise and physically active lifestyles modify it. For that reason, this study evaluates the associations between RER during sub-maximum exercise and other well established fitness indicators (body fat, maximum heart rate, maximum O₂ uptake, workload, and lactate threshold), in physically active trained and untrained men.

Methods:

The RER, O₂ uptake and blood lactate were measured in eight endurance trained and eight untrained men (age, 22.9 ± 4.5 vs. 21.9 ± 2.8 years; body mass, 67.1 ± 5.4 vs. 72.2 ± 7.7 kg; body fat, 10.6 ± 2.4% vs. 16.6 ± 3.8% and maximum O₂ uptake, 68.9 ± 6.3 vs. 51.6 ± 5.8 ml•kg⁻¹•min⁻¹), during maximum exercise test and during three different sub-maximum exercises at fixed workload: below, within or above the lactate threshold.

Results:

Endurance trained men presented higher O₂ uptake, lower blood lactate concentrations and lower RER values than those in untrained men at the three similar relative workloads. Even though with these differences in RER, a strong association (p < 0.05) of RER during sub-maximum exercise with the other well established fitness indicators was observed, and both maximum O₂ uptake and lactate threshold determined more than 57% of its variance (p < 0.05).

Conclusions:

These data demonstrate that RER measurement under sub-maximum exercise conditions was well correlated with other established physical fitness indicators, despite training condition. Furthermore, the results suggest that RER could help obtain an easy approach of fitness status under low exercise intensity and could be utilized in subjects with reduced exercise tolerance.

Peculiarities of the autonomic balance assessed through heart rate variability analysis in sportsmen and nonsportsmen

A comparative study was used to analyze the difference in autonomic balance assessed by time and frequency domain parameters of heart rate variability (HRV) between students athletes and non-sportsmen. Five-minute digital ECG trays were recorded in 21 students - athletes, 10 basketball players recruited from first league clubs of No- vi Sad and the Serbian representatives and 11 rowers from the Novi Sad rowing club 'Danubius'. The control group was formed by 15 non-sportsmen, students of the Medical faculty in Novi Sad who underwent the same registrations. Time and frequency-domain of HRV were analyzed by a software developed by the company 'Neurosoft', VNS-Spektr, Ivanovo, Russia. Resting heart rate in athletes was significantly lower (p < 0.01) than in non-sportsmen. In time-domain parameters HRV significantly higher values were present in the group of sportsmen as opposed to non-sportsmen RRNN (p < 0.01), RMSSD (p < 0.02) and pNN50 (p < 0.01). In frequency-domain of HRV statistically significant difference between the two groups was observed only in normalized values of LF and HF (p < 0.05) and their ratio LF/HF (p < 0.02). LFn was larger in non-sportsmen than in students-athletes. On the other hand HFn was larger in athletes than in non-sportsmen. The LF/HF ratio was larger in non-sportsmen (2.87 0.34) than in athletes (1.91 0.20). After dividing the athletes recruited for this investigation into two groups (basketball players and rowers) significant level of difference (p < 0.05) in HRV data was present only in the VLF spectrum (2060.55 290.68 ms2 for rowers and 1303.30 ? 169.95 ms2 for basketball players).

A nonlinear dynamic model for heart rate response to treadmill walking exercise

A dynamic model of the heart rate response to treadmill walking exercise is presented. The model is a feedback interconnected system; the subsystem in the forward path represents the neural response to exercise, while the subsystem in the feedback path describes the peripheral local response. The parameters of the model were estimated from 5 healthy adult male subjects, each undertaking 3 sets of walking exercise at different speeds. Simulated responses from the model closely match the experimental data both in the exercise and the recovery phases. The model will be useful in explaining the cardiovascular response to exercise and in the design of exercise protocols for individuals.

Methods to quantify intermittent exercises

The purpose of this study was to quantify intermittent training sessions using different types of exercise. Strength, sprint, and endurance sessions were performed until exhaustion. These sessions were quantified by the product of duration and heart rate (HR) (i.e., training impulse (TRIMP) and HR-zone methods), by the product of duration and rate of perceived exertion (RPE-based method), and a new method (work endurance recovery (WER)). The WER method aims to determine the level of exercise-induced physiological stress using the ratio of cumulated work - endurance limit, which is associated with the naparian logarithm of the ratio of work-recovery. Each session's effects were assessed using blood lactate, delayed onset muscle soreness (DOMS), RPE, and HR. Because sessions were performed until exhaustion, it was assumed that each session would have a similar training load (TL) and there would be low interindividual variability. Each method was used to compare each of the TL quantifications. The endurance session induced the higher HR response (p < 0.001), the sprint session the higher blood lactate increase (p < 0.001), and the strength session the higher DOMS when compared with sprint (p = 0.007). TLs were similar after WER calculations, whereas the HR- and RPE-based methods showed differences between endurance and sprint (p < 0.001), and between endurance and strength TL (p < 0.001 and p < 0.01, respectively). The TLs from WER were correlated to those of the HR-based methods of endurance exercise, for which HR was known to accurately reflect the exercise-induced physiological stress (r = 0.63 and r = 0.64, p < 0.05). In addition, the TL from WER presented low interindividual variability, yet a marked variability was observed in the TLs of HR- and RPE-based methods. As opposed to the latter two methods, WER can quantify varied intermittent exercises and makes it possible to compare the athletes' TL. Furthermore, WER can also assist in comparing athlete responses to training programs.

Changes in heart rate recovery in response to acute changes in training load

Heart rate recovery is an indirect marker of autonomic function and changes therein may offer a practical way of quantifying the physiological effects of training. We assessed whether per cent heart rate recovery (HRr%) after a standardized sub-maximal running (Heart rate Interval Monitoring System: HIMS) test, changed with acute changes in training load. A total of 28 men and women (mean age 30+/-5 years) trained ad libitum for 2 weeks during which their heart rate (HR) was recorded. Training load was quantified using Training Impulse (TRIMPs). The participants were grouped based on whether they increased (Group I, n=9), decreased (Group D, n=8) or kept their training load constant (Group S, n=11) from week 1 to week 2. Each week, the subjects completed a HIMS test. Changes between weeks in HR at the end of the test and HRr% were compared between groups. Mean per cent change in TRIMPs from week 1 to week 2 was significantly different among the groups (Group I, 55+/-21% vs Group S, -6+/-6% vs Group D, -42+/-16%; P<0.05). Group I had a slower HRr% and Group D tended to have a slightly faster HRr% after HIMS 2 than after HIMS 1 (mean per cent change 5.6+/-8.7 vs -2.6+/-3.9; P=0.03). Thus a negative effect on HRr was observed with increases in training load. Sub-maximal HR was not affected by acute changes in training load. Whereas HR during exercise measures cardiac load, HRr may reflect the state of the autonomic nervous system, indicating the body's capacity to respond to exercise.

Heart rate variability in trotters during different training periods

REASONS FOR PERFORMING STUDY

Endurance training induces changes in autonomic nervous system functions. High intensity training includes the risk of overtraining, in man and horse. Heart rate variability (HRV) is a noninvasive measurement of the autonomic regulation of the heart rate, which is quick and easy to measure with modern telemetric technology.

HYPOTHESIS

Since HRV is affected by changes in the autonomic nervous system, it might be an early stage indicator of poor recovery from a previous bout of exercise or overreaching or overtraining in horses in general.

METHODS

The aim of the study was to monitor recovery and the possible overtraining status in horses by measuring HRV. The measurements reflected the responses of the previous day activities during different training periods including basic training, precompetition and competition during a one-year follow-up.

RESULTS

HRV was at the highest during precompetition period (P<0.05) and it decreased significantly during competition period (P<0.05), indicating an increased stress load in the competition period. Walking increased HRV significantly compared to complete rest or jogging as previous day activities during basic training and precompetition periods (P<0.05). This finding suggests that horses are more relaxed during moderate exercise than standing still or anaerobic exercise.

CONCLUSIONS

HRV can be used to monitor the cardiovascular responses to training in horses but confirmatory measures may also be required in addition to HRV to exclude other possible causes of underperformance.

Heart rate measurements as an index of energy expenditure and energy balance in ruminants: A review1

A major part of the ME consumed by ruminants (MEI) is dissipated as heat. This fraction, called heat production or energy expenditure (EE), is assayed largely by measuring O2 consumption (VO2). Conventional measurement of EE in controlled conditions in chambers does not reflect the complexity of natural, environmental, and social conditions of free-ranging animals. In mammals, most of the measured VO2 is transferred to the tissues through the heart; therefore, regression of heart rate (HR) against VO2 can be used to estimate the EE of free-ranging animals. The present article reviews the current knowledge on the use of HR for estimating EE. Energy expenditure can be determined from HR measurements, recorded daily over the course of several days, multiplied by the VO2 per beat. When an animal does not perform significant exercise, a constant value of VO2 per beat [O2 pulse (O2P)] measured over a short period (10 to 15 min) is used; during exercise, O2P increases, and the regression equation of VO2 against HR is used. Under extreme heat load, HR increases to improve heat dissipation, and O2P decreases; therefore, the effect of heat load on O2P needs to be taken into account. Cold stress that doubles heat production does not affect O2P. Heart rate and EE are highly correlated with MEI, but there is significant individual variation in the relationship; therefore, the daily change in the HR of individual animals can be used as an indicator of changes in the individual energy status of a ruminant, and the average HR of the group can serve in the estimation of the energy status of the group. When O2P is measured, the average group EE is an indication of the energy balance of the whole group. Because the MEI of nondraft animals is the sum of EE and retained energy (RE), the MEI of free-ranging ruminants can be determined by measurement of EE by the HR method and adding the RE. Similarly, the RE can be determined without slaughtering the animals from measurements of EE and MEI. Soon when devices for automatic HR monitoring of domestic ruminants become available at a reasonable price, continuous monitoring of HR might provide producers with a sensitive tool for identifying changes in the energy status of their animals. This will also significantly help to shorten the time needed to identify health problems of individual animals.

Practical tests for monitoring performance, fatigue and recovery in triathletes

Few studies have described simple tests which can be used to provide an early warning of overreaching. The purpose of this study was to examine selected practical tests for monitoring changes in performance, fatigue and recovery of endurance athletes. Sixteen male triathletes were randomly assigned into matched groups. The normal training (NT) and intensified training (IT) groups completed 4 weeks of training followed by a 2-week taper. Physiological measures were taken pre- and post-overload and post-taper periods during an incremental treadmill test to exhaustion. Performance was assessed weekly using a 3-km run time trial (3 kmTT). Five-bound jump for distance (5BT) and submaximal running heart rate (HR(submax)) test were measured twice weekly and the Daily Analyses of Life Demands for Athletes (DALDA) were recorded. During the overload training period, the IT group completed approximately 290% more training load than the NT group (p<0.001). After the overload training period, 3kmTT in the IT group was reduced compared to both pre-training (3.7%, p<0.05) and the NT group (6.8%, p<0.05). 5BT was decreased by 7.9% in the IT group following the overload period (p<0.05). The IT group also demonstrated increases in stress reaction symptoms from the DALDA. Following the taper, the IT group improved 3 kmTT. In contrast, the performance, physiological and psychological markers of NT group remained relatively unchanged throughout the 6-week training period. There were weak significant correlations between weekly changes in 3 kmTT and 5BT (r=-0.37, p<0.01). The DALDA and 5BT may be practical tests for assessing changes in performance, fatigue and recovery of endurance athletes.

Estimation of total daily energy expenditure and its components by monitoring the heart rate of Japanese endurance athletes

The estimation of total daily energy expenditure (TEE) or the energy needs of athletes is important for maintaining a proper energy balance during training. This study was conducted to measure the TEE of Japanese middle- and long-distance runners using a heart-rate monitoring method (the HR method), and to ascertain the impact of three key energy expenditure (EE) components occurring within the day: sleep, exercise (training) and inactivity (other daily habitual activities). Additionally, energy balance was evaluated by comparing TEE with energy intake (EI). The mean TEE of six male athletes aged 19-21 y was 4,514+/-739 kcal/d and their mean EI was 3,784+/-91 kcal/d during the training period of 11 d. This negative energy balance led to a significant decline in body weight (p<0.01), indicating that proper care should be taken to balance energy during training. The mean daily EEs during sleep, inactivity, and exercise were 536+/-46 (12.0% of TEE), 1,722+/-145 (38.7%), and 2,255+/-658 (49.3%) kcal/d, respectively. There was a significant correlation between TEE and exercise EE (p<0.01) in the athletes. The TEE of the endurance athletes was higher than expected and significantly affected by exercise EE, indicating that the TEE of athletes, in general, must be carefully evaluated before incorporating nutritional support for them.

Physiological Aspects of Soccer Refereeing Performance and Training

The role of the referee is far from minimal in the economy of soccer, as very often, particularly in professional soccer, a wrong judgment may have profound implications on the outcome of the game. In this regard, a better knowledge of soccer refereeing can obviously benefit the game. Recent studies have shown that during a competitive match, an elite soccer referee may cover 9-13 km attaining approximately 85-90% and approximately 70-80% of maximal heart rate and maximal oxygen uptake (VO2max), respectively. Of the total distance covered about 4-18% is covered at high intensity. Blood lactate concentration has been reported to be in the range of 4-5 mmol/L; however, during competitive matches, blood lactate concentrations as high as 14 mmol/L have been observed. This figure is similar to that extensively reported for soccer players, specifically paralleling that observed in midfield players. However, compared with players, referees are 15-20 years older, often have a non-professional status and cannot be substituted during the game. Furthermore, this important physical stress superimposes onto a high perceptual-cognitive workload throughout the entire game. In relation to fitness status, referees possess VO2max values somewhat lower than the players they officiate, with mean values in the range of 44-50 mL/kg/min. However, the methods used by the Federation Internationale de Football Association and the Union of European Football Associations to test referee fitness need to be changed as the current fitness tests do not relate to match performance. More task-specific tests such as the Yo-Yo Intermittent Recovery Test (YYIRT) have been devised and validated for use with referees. Given that aerobic performance is positively correlated with match performance, it is important that referees are trained to improve their ability to cover large distances during a match and also to repeat high-intensity efforts. A number of studies have shown large improvements in YYIRT performance following both short-term (12 weeks) and long-term (16 months) high-intensity interval training. Future research needs to focus on a number of important areas including the decision-making ability of referees when officiating under different conditions, such as high thermal strain, and the impact of age on both physical and mental performance.

Devices for ambulatory and home monitoring of blood pressure, lipids, coagulation, and weight management, part 2

PURPOSE

The equipment and methods used for ambulatory and home monitoring of blood pressure, lipids, coagulation, and weight management are discussed.

SUMMARY

Over 100 million people in the United States have one or more chronic diseases, such as diabetes, hypertension, and asthma. With the goal to improve health while reducing costs and the overall health care burden, ambulatory and home monitoring by pharmacists and patients are receiving more attention. Ambulatory and home monitoring of blood pressure, cholesterol, coagulation, and weight management (including devices for assessing overweight and obese patients, heart rate monitors, and pedometers) are convenient for clinicians and patients. Such monitoring provides pharmacists with an opportunity to differentiate their practices. Studies suggest that patients who are involved in ambulatory and home monitoring take a more active role in their health and may have better adherence to a prescribed diet and medication regimens. Studies also show that ambulatory and home monitoring, if done correctly, provide clinicians with a large quantity of reliable readings for future therapeutic decisions. Devices are also a means for pharmacists to increase their provision of pharmacy services. Ambulatory monitoring is billable in many clinic settings, and the devices can be a profitable addition to prescription services.

CONCLUSION

Many devices are available to assist patients and clinicians in monitoring blood pressure, lipids, coagulation, and weight management. Familiarity with the devices will help in their proper selection and use.

Independência temporal das respostas do esforço percebido e da freqüência cardíaca em relação à velocidade de corrida na simulação de uma prova de 10km

O objetivo do presente estudo foi investigar a estratégia de corrida, o esforço percebido e a freqüência cardíaca durante a simulação de uma competição de corrida. Nove corredores recreacionais percorreram a distância de 10km em uma pista de atletismo descoberta, com a temperatura ambiente variando entre 28 e 30ºC. Antes do início da prova foi solicitado aos corredores que percorressem a distância de 10km "na maior velocidade possível". A velocidade de corrida, o esforço percebido e a freqüência cardíaca foram mensurados nas parciais de 400m. A velocidade de corrida diminuiu na 19ª e na 20ª parciais (p < 0,05). A freqüência cardíaca aumentou significativamente na sétima e na 10ª voltas (p < 0,05) e posteriormente estabilizou-se, ao passo que o esforço percebido aumentou estatisticamente até a 13ª volta (p < 0,05). Esses dados sugerem que a estratégia de corrida, o esforço percebido e a freqüência cardíaca possuem ajustes temporais distintos durante as provas de corridas. Possivelmente, a estratégia de corrida é estabelecida antes da simulação da competição e possui um aspecto poupador para um possível sprint. Esse efeito poupador da estratégia de corrida parece ser determinado principalmente até a metade da prova pela modulação do esforço percebido, que é resultante de um processo de retroalimentação metabólico, contextual e cognitivo.

Cardiovascular responses during recreational 5-a-side indoor-soccer

The aims of this study were to examine the cardiovascular response to recreational 5-a-side indoor-soccer (5v5) matches (5v5 study, 5v5S, n=15) and to assess the validity of using heart rate (HR) to estimate oxygen uptake (VO(2)) demands during actual game-play (validity study, VS, n=16) in young subjects (age 16.8+/-1.5 years). Game responses during 5v5S were assessed during 30 min matches using short-range telemetry heart-rate monitors. In VS games (12 min), VO(2) and HR were monitored with a portable gas analyser (K4b(2), COSMED, Rome, Italy). Individual HR-VO(2) relationships were determined from a laboratory treadmill run to exhaustion (VS) and a multistage shuttle running fitness test (5v5S) using K4b(2). Results showed that 5v5 elicits 83.5+/-5.4 and 75.3+/-11.2% of HR(peak) and VO(2peak), respectively. Ninety-one percent of the playing time (30 min) was spent at HR higher than 70% of HR(peak). In VS match, gas analyses revealed that only 71% of HR variance was explained by VO(2) variations. However, playing at approximately 70% of HR(peak) elicited 51.6+/-11.2% of VO(2peak). Group actual versus predicted VO(2) values demonstrated no significant differences (p>0.05), however, large confidence limits were observed (+6.20 and -10.53 mlkg(-1)min(-1)). These results show that HR and VO(2) responses to recreational 5v5 soccer in young athletes are similar to the exercise intensities recommended by ACSM for promoting cardiovascular health and suggest that HR is valid to prescribe and monitor aerobic intermittent exercise. These results also show that HR measures are acceptable for estimating VO(2) during intermittent exercise when assessing large groups, but show that large estimation errors can occur at the individual level.

Comportamento de variáveis fisiológicas em atletas de nado sincronizado durante uma sessão de treinamento na fase de preparação para as Olimpíadas de Atenas 2004

O objetivo do presente estudo foi avaliar o comportamento de variáveis fisiológicas durante uma sessão de treino de nado sincronizado realizada na fase de preparação para as Olimpíadas de Atenas 2004. MATERIAIS E MÉTODOS: A amostra utilizada foi constituída pelo dueto (24 ± 0 anos) representante do Brasil em Atenas 2004. A coleta de dados foi realizada durante uma sessão de treinamento com duração de 198 minutos. O treino se iniciou com a parte física, seguida da parte técnica. Para a determinação da glicemia e da concentração de beta-hidroxibutirato foi utilizado o monitor Optium® com suas respectivas tiras. As concentrações de cortisol e das enzimas lactato desidrogenase (LDH) e creatina quinase (CK) foram determinadas por radioimunoensaio (DPC©) e kits comerciais (CELM®), respectivamente. O acompanhamento da freqüência cardíaca (FC) foi realizado com o freqüêncimetro Advantage Polar®. RESULTADOS: Foi observada redução (~2%) do peso corporal. A glicemia também apresentou queda (~30%) em comparação ao valor obtido no início do treino. Em contrapartida, foi observada elevação na concentração de cortisol (salivar 22% e plasmática 29%) e de beta-hidroxibutirato (~340%). Não foi observada alteração significativa na concentração plasmática de CK e de LDH. O acompanhamento da FC demonstrou que dos 198 minutos que constituíram a sessão de treino, 36,5 ± 0,7 minutos foram realizados em intensidade leve; 103,5 ± 0,7 minutos em intensidade moderada, 54,0 ± 2,1 minutos em intensidade alta e 4,0 ± 0,0 minutos em intensidade muito alta. CONCLUSÕES: A perda de peso indica que a reposição hídrica não foi adequada. A redução na glicemia e o aumento na concentração de corpos cetônicos e de cortisol reforçam a importância da suplementação de carboidrato durante o treino de longa duração. O comportamento da FC demonstra que a sessão de treinamento foi realizada em uma intensidade moderada, porém com breves momentos de intensidade alta, nos quais foram realizadas as rotinas.

Physiological assessment of aerobic training in soccer

Physiological assessment of soccer training usually refers to the measurement of anatomical, physiological, biochemical and functional changes specific to the sport discipline (training outcome). The quality, quantity and organization of physical exercises (training process) are, on the other hand, usually described by the external work imposed by the coach on his or her athletes. In this review, we demonstrate that this approach is not appropriate in soccer, as training is often based on group exercises. The physiological stress (internal load) induced by such training often differs between individuals. Here, we present some physiological laboratory-based tests and field tests used to evaluate training outcomes in soccer, together with methods based on heart rate and perceived exertion to quantify internal load imposed during training. The integrated physiological assessment of both training outcome and process allows researchers: (1) to improve interpretation of physical tests used to verify the effectiveness of training programmes; (2) to evaluate the organization of the training load in order to design periodization strategies; (3) to identify athletes who are poor responders; (4) to control the compliance of the training completed to that planned by the coach; and (5) to modify the training process before the assessment of its outcome, thus optimizing soccer performance.

Respostas da freqüência cardíaca de pico em testes máximos de campo e laboratório

FUNDAMENTOS E OBJETIVO: A freqüência cardíaca de pico (FCpico) obtida em testes máximos de laboratório é utilizada para a prescrição da intensidade do exercício aeróbio em situações de campo. Contudo, valores de FCpico podem diferir em situações de campo e laboratório, influenciando na determinação da intensidade relativa do esforço. O objetivo do estudo foi verificar as respostas de FCpico em testes máximos de campo e laboratório, analisando suas influências na prescrição do exercício. MÉTODOS: Foram avaliados 25 homens fisicamente ativos, com idade entre 20 e 51 anos (28,9 ± 8,5 anos). Os indivíduos realizaram testes de 2.400 metros em pista oficial de atletismo e protocolos máximos de rampa em laboratório. Todos os testes foram feitos em um intervalo de duas semanas, com ordem alternada para cada indivíduo. Antes de cada teste eram aferidas a umidade do ar e a temperatura ambiente. Nas 48 horas precedentes, os indivíduos eram instruídos a não realizar atividades físicas. Possíveis diferenças nas respostas de FCpico, e condições ambientais (temperatura e umidade relativa do ar) em campo e laboratório, foram testadas pelo teste t de Student emparelhado e simples, respectivamente (p < 0,05). RESULTADOS: Os valores de FCpico foram significativamente maiores no teste de campo, as diferenças podendo chegar a 10 batimentos em alguns casos. Essas diferenças podem ser parcialmente explicadas pelo fato de a temperatura e umidade do ar terem sido maiores no campo. CONCLUSÃO: Conclui-se que testes de campo tendem a provocar maior FCpico que protocolos de laboratório, parecendo ser mais indicados para determinar a intensidade relativa do esforço aeróbio no treinamento físico.

Physiological changes associated with the pre-event taper in athletes

Some of the physiological changes associated with the taper and their relationship with athletic performance are now known. Since the 1980s a number of studies have examined various physiological responses associated with the cardiorespiratory, metabolic, hormonal, neuromuscular and immunological systems during the pre-event taper across a number of sports. Changes in the cardiorespiratory system may include an increase in maximal oxygen uptake, but this is not a necessary prerequisite for taper-induced gains in performance. Oxygen uptake at a given submaximal exercise intensity can decrease during the taper, but this response is more likely to occur in less-skilled athletes. Resting, maximal and submaximal heart rates do not change, unless athletes show clear signs of overreaching before the taper. Blood pressure, cardiac dimensions and ventilatory function are generally stable, but submaximal ventilation may decrease. Possible haematological changes include increased blood and red cell volume, haemoglobin, haematocrit, reticulocytes and haptoglobin, and decreased red cell distribution width. These changes in the taper suggest a positive balance between haemolysis and erythropoiesis, likely to contribute to performance gains. Metabolic changes during the taper include: a reduced daily energy expenditure; slightly reduced or stable respiratory exchange ratio; increased peak blood lactate concentration; and decreased or unchanged blood lactate at submaximal intensities. Blood ammonia concentrations show inconsistent trends, muscle glycogen concentration increases progressively and calcium retention mechanisms seem to be triggered during the taper. Reduced blood creatine kinase concentrations suggest recovery from training stress and muscle damage, but other biochemical markers of training stress and performance capacity are largely unaffected by the taper. Hormonal markers such as testosterone, cortisol, testosterone : cortisol ratio, 24-hour urinary cortisol : cortisone ratio, plasma and urinary catecholamines, growth hormone and insulin-like growth factor-1 are sometimes affected and changes can correlate with changes in an athlete's performance capacity. From a neuromuscular perspective, the taper usually results in markedly increased muscular strength and power, often associated with performance gains at the muscular and whole body level. Oxidative enzyme activities can increase, along with positive changes in single muscle fibre size, metabolic properties and contractile properties. Limited research on the influence of the taper on athletes' immune status indicates that small changes in immune cells, immunoglobulins and cytokines are unlikely to compromise overall immunological protection. The pre-event taper may also be characterised by psychological changes in the athlete, including a reduction in total mood disturbance and somatic complaints, improved somatic relaxation and self-assessed physical conditioning scores, reduced perception of effort and improved quality of sleep. These changes are often associated with improved post-taper performances. Mathematical models indicate that the physiological changes associated with the taper are the result of a restoration of previously impaired physiological capacities (fatigue and adaptation model), and the capacity to tolerate training and respond effectively to training undertaken during the taper (variable dose-response model). Finally, it is important to note that some or all of the described physiological and psychological changes associated with the taper occur simultaneously, which underpins the integrative nature of relationships between these changes and performance enhancement.

Cardiopulmonary physiology and responses of ultramarathon athletes to prolonged exercise

The purpose of this study was to determine the changes of pulmonary function and autonomic cardiovascular control after an ultramarathon and their relation to performance. Eight entrants to the Canadian National Championship 100-km running race participated in the study. Pulmonary function and 30-s maximum voluntary ventilation (MVV30s) tests were conducted one day before the race and within 5 minutes of race completion. Heart rate and blood pressure data were collected 30 min before and 5 min after the race as well as during a 10-min stand test one day prior to the race. During the race, beat-by-beat R-R interval data were collected over the first and last 20 km. The results showed that MVV30s and MVV30s tidal volumes were reduced postrace (p < 0.001). Prerace supine total harmonic variation (p < 0.01) and prerace MVV values (10 s to 30 s) (p < 0.05) were correlated with race finish time. The changes in pulmonary function and MVV30s values from pre- and postrace were not significantly correlated to race performance. We conclude that maximal sustainable ventilatory power and dynamic autonomic cardiovascular control are important factors in determining overall performance in an ultramarathon.

Eccentric Cycle Exercise: Training Application of Specific Circulatory Adjustments

PURPOSE

Despite identical oxygen uptake (VO2), enhanced heart rate (HR) and cardiac output (Q) responses have been reported in eccentric (ECC) versus concentric (CON) cycle exercise. The aim of this study was to describe the specific circulatory adjustments (HR and stroke volume (SV)) to incremental ECC cycle exercise in order to: 1) determine the HR values leading to identical VO2 in ECC and CON cycling; and 2) estimate the interindividual variability of this HR correspondence between the two exercise modes, with emphasis upon rehabilitation and training purposes.

METHODS

Eight healthy male subjects (age, 28 +/- 2 yr) participated in this study. They performed CON and ECC cycle incremental exercises (power output increases of 50 W every 3 min). Breath-by-breath gas exchange analysis and beat-by-beat thoracic impedancemetry were used to determine VO2 and Q, respectively.

RESULTS

At the same metabolic power (VO2 of 1.08 +/- 0.05 L x min(-1) in CON vs 1.04 +/- 0.06 L x min in ECC), SV was not different, but HR was 17% higher in ECC (P < 0.01), leading to a 27% enhanced Q (P < 0.01). Q and HR net adjustments (exercise minus resting values) in ECC versus CON muscle involvement demonstrated important interindividual variability with coefficients of variation amounting to 32% and 30%, respectively.

CONCLUSION

In practice, if a given level of VO2 is to be reached, ECC HR has to be set above the CON one. Taking into account the interindividual variability of the circulatory adjustments in ECC versus CON muscle involvement, a precise HR correspondence can be established individually from the VO2/HR relationship obtained using ECC incremental testing, allowing prescription of accurate target HR for rehabilitation or training purposes.

Use of RPE-Based Training Load in Soccer

PURPOSE

The ability to accurately control and monitor internal training load is an important aspect of effective coaching. The aim of this study was to apply in soccer the RPE-based method proposed by Foster et al. to quantify internal training load (session-RPE) and to assess its correlations with various methods used to determine internal training load based on the HR response to exercise.

METHODS

Nineteen young soccer players (mean +/- SD: age 17.6 +/- 0.7 yr, weight 70.2 +/- 4.7 kg, height 178.5 +/- 4.8 cm, body fat 7.5 +/- 2.2%, VO2max, 57.1 +/- 4.0 mL x kg x min) were involved in the study. All subjects performed an incremental treadmill test before and after the training period during which lactate threshold (1.5 mmol x L above baseline) and OBLA (4.0 mmol x L) were determined. The training loads completed during the seven training weeks were determined multiplying the session RPE (CR10-scale) by session duration in minutes. These session-RPE values were correlated with training load measures obtained from three different HR-based methods suggested by Edwards, Banister, and Lucia, respectively.

RESULTS

Individual internal loads of 479 training sessions were collected. All individual correlations between various HR-based training load and session-RPE were statistically significant (from r = 0.50 to r = 0.85, P < 0.01).

CONCLUSION

The results of this study show that the session-RPE can be considered a good indicator of global internal load of soccer training. This method does not require particular expensive equipment and can be very useful and practical for coaches and athletic trainer to monitor and control internal load, and to design periodization strategies.

The impact of specific high-intensity training sessions on football referees' fitness levels

BACKGROUND

In comparison to the amount of literature that has examined the match demands of football refereeing, there has been little attempt to assess the impact of high-intensity training.

PURPOSE

The main goals were to get a better understanding of the long-term effect of specific intermittent training.

STUDY DESIGN

The authors examined the cardiovascular strain of specific high-intensity training sessions and also their impact on referees' fitness levels.

METHODS

To examine the physical workload during intensive intermittent training sessions, heart rates were recorded and analyzed relative to the referees' maximum heart rate (HR(max)). To assess the referees' fitness levels, the Yo-Yo intermittent recovery test was used.

RESULTS

Both the pitch- and track-training sessions were successful in imposing an appropriate high intensity load on the referees, at 86.4 +/- 2.9% and 88.2 +/- 2.4% HR(max), respectively. Following 16 months of intermittent high-intensity training, referees improved their performance on the Yo-Yo intermittent recovery test by 46.5%, to a level that is comparable with professional players.

CONCLUSIONS

As match officials are subjected to a high physical load during matches, they should follow structured weekly training plans that have an emphasis on intensive, intermittent training sessions.