Heart rate-index estimates aerobic metabolism in professional soccer players

Assessment of Aerobic Fitness and Repeated Sprint Ability in Elite Male Soccer: A Systematic Review of Test Protocols Used in Practice and Research

BACKGROUND

Soccer requires players to cover distances around 10-12 km, with numerous consecutive sprints throughout the 90-min game. As such, aerobic fitness and repeated sprint ability (RSA) are crucial physical qualities for the modern soccer player to cope with the demands of the game. However, a comprehensive and systematic search of aerobic fitness and RSA assessment procedures in elite soccer has yet to be conducted.

OBJECTIVES

The aims of this systematic review were to (1) identify the tests and outcome variables used to assess aerobic fitness and RSA of elite male soccer players, (2) provide normative values for the most common tests of aerobic fitness and RSA across different playing levels, and (3) report the reliability values of these aerobic fitness and RSA tests.

METHODS

A systematic review of the academic databases MEDLINE, CINAHL, SPORTDiscus, Web of Science, and OVID for studies published until August 2023 was conducted, following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Studies were eligible for inclusion if (1) they were original research studies, published in a peer-reviewed journal, and written in English language; (2) they had the primary aim of assessing aerobic fitness and/or RSA; (3) players were male and older than 17 years of age (i.e. mean age of the group); and (4) their playing level was defined as 'professional', 'international', or 'elite'.

RESULTS

For aerobic fitness testing, 124 studies and 35 different tests were identified. Of those, 26 tests (74%) were field-based, whereas only nine (26%) were laboratory-based tests. The incremental treadmill test to exhaustion was the most commonly used aerobic fitness assessment method (56 studies, 45%), with maximal oxygen consumption ( V ˙ O2max) (mL/kg/min) being the most prevalent outcome variable (49 studies, 87%). The YYIR1 and YYIR2 were also commonly used tests, identified in 22 (18%) and ten studies (8%), respectively. The most frequently reported outcome variable in both tests was distance in metres, reported in 20 studies (91%) for YYIR1 and in all ten studies (100%) for YYIR2. For RSA testing, 27 studies and 18 different tests were identified. Substantial variability in the identified RSA testing protocols was observed in terms of direction (linear vs. multidirectional), sprint repetitions (6-15), sprint distance (20-40 m), type of recovery (active vs. passive), and recovery duration (10-30 s). The 6 × 40-m shuttle sprint protocol with a 180° change of direction and 20 s passive recovery was the most common RSA test, employed in eight studies (29%).

CONCLUSIONS

This systematic review provides a comprehensive overview of the testing methods used to assess aerobic fitness and RSA in elite male soccer players. A total of 35 different aerobic fitness tests and 18 RSA tests were identified, highlighting the diversity in methodologies used. The most prevalent aerobic test was the incremental treadmill testing to exhaustion, with a median V ˙ O2max value of 58 mL/kg/min. Field-based tests were preferred due to their practicality, cost-efficiency, and ability to assess multiple athletes simultaneously. A substantial variability in RSA testing protocols was identified in terms of sprint directions, distances, repetitions, and recovery types. Future research should focus on establishing the diagnostic accuracy of the most commonly used aerobic fitness tests to inform their utility in practice and bridge the gap between current testing practices and optimal fitness evaluation.

Heart Rate Index-An Alternative Exercise-Based Equation for Estimating Peak VO 2

PURPOSE

Heart rate (HR)-derived variables (HR reserve [HR peak  - HR rest ], chronotropic indices [attenuated HR response to exercise], HR recovery [attenuated HR response to exercise recovery], and peak HR index [HR peak /HR rest ]) together with peak oxygen uptake (VO 2peak ) are potential prognostic variables for cardiovascular and all-cause mortality. However, heart rate index (HRI) has not been established as a surrogate for VO 2peak , whether measured (Meas) or estimated (Est), during cycle ergometry (CE) and/or treadmill testing (TT).

METHODS

HR-derived prognostic variables to assess cardiovascular outcomes were identified from 150 studies obtained from MEDLINE and Google Scholar searches. The Meas CE/TT-VO 2peak was reported in 81 studies (21 773 participants) and Est CE/TT-VO 2peak in 69 studies (331 435 participants). Using the HRI equation with metabolic equivalent (METs) = 6 × HRI - 5 (where HRI = peak HR/resting HR), HRI-VO 2peak was calculated from HR data reported in the 150 studies. The HRI-VO 2peak was then compared against group mean data for both Meas CE/TT-VO 2peak and Est CE/TT-VO 2peak .

RESULTS

The difference between Meas CE/TT-VO 2peak and HRI-VO 2peak was 1% (7.15 ± 3.25 METs vs 7.08 ± 3.02 METs [ P = .833], respectively). By comparison, the difference between Est CE/TT-VO 2peak and HRI-VO 2peak was 25.6% (8.94 ± 2.36 METs vs 7.12 ± 2.27 METs [ P < .001], respectively). Moreover, HRI equation estimation of VO 2peak showed greater overprediction for TT, 26.6%, than for CE, 11.9%.

CONCLUSIONS

The Meas-VO 2peak and HRI-VO 2peak agreed closely. When compared with HRI-VO 2peak , Est-VO 2peak from currently used exercise-based equations shows significant overprediction. Use of HRI and/or Fitness Registry and the Importance of Exercise National Database (FRIEND) registry equations warrant consideration for more accurately estimating VO 2peak .

Predicting Heart Rate Slow Component Dynamics: A Model Across Exercise Intensities, Age, and Sex

The heart rate slow component (scHR) is an intensity-dependent HR increment that emerges during constant exercises, partially dissociated from metabolism (V˙O2). The scHR has been observed during constant-workload exercise in young and older adults. Unless this scHR is accounted for, exercise prescription using HR targets lead to an undesired reduction in metabolic intensity over time.

PURPOSE

The purpose of this study is to characterize scHR across intensities, sex, and age to develop and validate a predictive equation able to maintain the desired metabolic stimulus over time in a constant aerobic exercise session.

METHODS

In our study, 66 individuals (35 females; 35 ± 13 yrs) performed the following: (i) a ramp-test for respiratory exercise threshold (GET and RCP) and maximal oxygen uptake (V˙O2max) detection, and (ii) 6 × 9-minute constant exercises at different intensities. The scHR was calculated by linear fitting from the fifth minute of exercise (bpm⋅min-1). A multiple-linear equation was developed to predict the scHR based on individual and exercise variables. The validity of the equation was tested on an independent sample by a Pearson correlation and Bland-Altman analysis between the measured and estimated HR during constant exercises.

RESULTS

The scHR increases with intensity and is larger in males (p < 0.05). A multiple-linear equation predicts the scHR based on the relative exercise intensity to RCP, age, and sex (r2 = 0.54, SEE = 0.61 bpm⋅min-1). scHR (bpm⋅min-1) = -0.0514 + (0.0240 × relative exercise intensity to RCP) - (0.0172 × age) - (0.347 × Sex (males = 0 and females score = 1)). In the independent sample, we found an excellent correlation between the measured and estimated HR (r2 = 0.98, p < 0.001) with no bias (-0.01 b·min-1, z-score= -0.04) and a fair precision (±4.09 b·min-1).

CONCLUSIONS

The dynamic of the scHR can be predicted in a heterogeneous sample accounting for the combined effects of relative intensity, sex, and age. The above equation provides the means to dynamically adapt HR targets over time, avoiding an undesired reduction in the absolute and relative training load. This strategy would allow the maintenance of the desired metabolic stimulus (V˙O2) throughout an exercise session in a heterogeneous population.

Speed Effects on the Accuracy of Heart Rate as Oxygen-Uptake Indicator in Short-Distance Shuttle Running

Purpose: Despite the accuracy of heart rate (HR) as an indicator of the aerobic engagement has been evaluated in several intermittent on-court activities, its validity as an oxygen uptake (V ˙ O 2 ) indicator during shuttle running over short paths remains uncertain. Moreover, it is unclear whether speed may affect such validity. This study evaluated the HR ability in estimating the V ˙ O 2 during 5-m shuttle running at different speeds. Methods: V ˙ O 2 and HR of 12 physically active young men were recorded during an incremental forward running (FW) protocol and a 5-m shuttle test at 50%, 60%, and 75% of maximal aerobic speed (MAS). Slope and intercept of the relationship between HR and V ˙ O 2 (HR/V ˙ O 2 ) were individually determined, in both protocols. The HR measured during the shuttle test was used in the FW HR/V ˙ O 2 to estimate V ˙ O 2 at each shuttle speed. A paired Student's t-test compared slopes and intercepts of the two HR/V ˙ O 2 . A two-way RM-ANOVA and an equality test examined, respectively, the differences and the equality between measured and estimated V ˙ O 2 . Lastly, a Bland-Altman plot described the accuracy and precision of the estimated V ˙ O 2 at each shuttle intensity. Results: Slopes and intercepts of the HR/V ˙ O 2 appeared not different between FW and shuttle running. At 50%MAS, HR underestimated the V ˙ O 2 (~7%), whereas returned accurate values at the two higher velocities, although with high variability (±18%). Conclusions: When using HR as V ˙ O 2 indicator during shuttle running over short paths, a separated analysis of the HR validity as V ˙ O 2 indicator is recommended especially when administering different exercise intensities.

Application and performance of heart-rate-based methods to estimate oxygen consumption at different exercise intensities in postmenopausal women

PURPOSE

Heart rate (HR) is a widespread method to estimate oxygen consumption ( V ˙ O2), exercise intensity, volume, and energy expenditure. Still, accuracy depends on lab tests or using indexes like HRnet and HRindex. This study addresses HR indexes' applicability in postmenopausal women (PMW), who constitute over 50% of the aging population and may have unique characteristics (e.g., heart size) affecting HR use.

METHODS

Fourteen PMW underwent a cycling ramp incremental test to establish the relationships between V ˙ O2 (in MET) and absolute HR, HRnet, and HRindex. In a second group of ten PMW, population-specific and general equations were tested to predict MET and energy expenditure during six constant work exercises at various intensities. Pulmonary gas exchange and HR were continuously measured using a metabolic cart. Correlations, Bland-Altman analysis, and two-way RM-ANOVA were used to compare estimated and measured values.

RESULTS

Strong linear relationships between the three HR indexes and MET were found in Group 1. In Group 2, population-specific equations showed medium-to-high correlations, precision, and no significant biases when estimating MET and energy expenditure. HRnet and HRindex outperformed absolute HR in accuracy. General HR equations had similar correlations but exhibited larger biases and imprecision. Statistical differences between measured and estimated values were observed at all intensities with general equations.

CONCLUSION

This investigation confirms the suitability of HR for estimating aerobic metabolism in one of the most significant aging populations. However, it emphasizes the importance of considering individual variability and developing population-specific models when utilizing HR to infer metabolism.

In professional football the decline in high-intensity running activities from first to second half is more pronounced in players with a fast muscle typology

Muscle typology is heterogeneous among national level football (soccer) players, but positional differences remain unclear. Furthermore, fast typology (FT) individuals fatigue more than slow typology (ST) individuals in lab conditions. Therefore, we investigated if muscle typology is different between playing positions and if the decay in high-intensity activities from the first to the second half is larger in FT football players than in ST players. We estimated muscle typology in 147 male professional football players by measuring soleus and gastrocnemius muscle carnosine via proton magnetic resonance spectroscopy. Players were classified as ST, intermediate typology (IT) or FT and categorized as goalkeeper, center back, full back, midfielder, winger or forward. Across four seasons in-game distances covered in multiple running speed, acceleration and deceleration zones were collected during the first and second half. We found no differences in muscle typology between positions (p = 0.412). FT players covered 10.9% more high acceleration distance (>3 m.s-2 ) in the first half than ST players (p = 0.021) and high acceleration distance decay was larger for FT players (-12.4%) than ST (-7.7%; p = 0.006) and IT players (-7.3%; p = 0.010). Moreover, the decline in distance covered in several high-intensity zones tended to be larger in FT players (-11.2% high-intensity >15 km.h-1 ; -12.7% high deceleration <-3 m.s-2 ; -11.5% medium acceleration 2-3 m.s-2 ) than in ST players (-7.1% high-intensity; -8.1% high deceleration; -8.1% medium acceleration; 0.05 < p < 0.1). In conclusion, possessing a particular muscle typology is not required to play any football position at the national level. However, there are indications that FT players might fatigue more toward the end of the game compared to ST players.

Easy Prediction of the Maximal Lactate Steady-State in Young and Older Men and Women

Maximal Lactate steady-state (MLSS) demarcates sustainable from unsustainable exercise and is used for evaluation/monitoring of exercise capacity. Still, its determination is physically challenging and time-consuming. This investigation aimed at validating a simple, submaximal approach based on blood lactate accumulation ([Δlactate]) at the third minute of cycling in a large cohort of men and women of different ages. 68 healthy adults (40♂, 28♀, 43 ± 17 years (range 19-78), VO_2max 45 ± 11 ml^-1·kg^-1·min^-1 (25-68)) performed 3-5 constant power output (PO) trials with a target duration of 30 minutes to determine the PO corresponding to MLSS. During each trial, [Δlactate] was calculated as the difference between the third minute and baseline. A multiple linear regression was computed to estimate MLSS based on [Δlactate], subjects` gender, age and the trial PO. The estimated MLSS was compared to the measured value by paired t-test, correlation, and Bland-Altman analysis. The group mean value of estimated MLSS was 180 ± 51 W, not significantly different from (p = 0.98) and highly correlated with (R² = 0.89) measured MLSS (180 ± 54 watts). The bias between values was 0.17 watts, and imprecision 18.2 watts. This simple, submaximal, time- and cost-efficient test accurately and precisely predicts MLSS across different samples of healthy individuals (adjusted R² = 0.88) and offers a practical and valid alternative to the traditional MLSS determination.

Impact and workload are dominating on-field data monitoring techniques to track health and well-being of team-sports athletes

Participation in sports has become an essential part of healthy living in today's world. However, injuries can often occur during sports participation. With advancements in sensor technology and data analytics, many sports have turned to technology-aided, data-driven, on-field monitoring techniques to help prevent injuries and plan better player management. This review searched three databases, Web of Science, IEEE, and PubMed, for peer-reviewed articles on on-field data monitoring techniques that are aimed at improving the health and well-being of team-sports athletes. It was found that most on-field data monitoring methods can be categorized as either player workload tracking or physical impact monitoring. Many studies covered during this review attempted to establish correlations between captured physical and physiological data, as well as injury risk. In these studies, workloads are frequently tracked to optimize training and prevent overtraining in addition to overuse injuries, while impacts are most often tracked to detect and investigate traumatic injuries. This review found that current sports monitoring practices often suffer from a lack of standard metrics and definitions. Furthermore, existing data-analysis models are created on data that are limited in both size and diversity. These issues need to be addressed to create ecologically valid approaches in the future.

An Intensity-dependent Slow Component of HR Interferes with Accurate Exercise Implementation in Postmenopausal Women

Heart rate (HR) targets are commonly used to administer exercise intensity in sport and clinical practice. However, as exercise protracts, a time-dependent dissociation between HR and metabolism can lead to a misprescription of the intensity ingredient of the exercise dose.