An Assessment of Heart Rate as a Tool for the Monitoring of Physiological Status in Soccer Players Following Competitive Match-play
The area of recovery following soccer match play has become an increasingly popular area of focus in recent years. There is limited research around the activities and monitoring processes undertaken within elite soccer clubs. To the authors knowledge, there is only one previous research article that has attempted to understand the activities undertaken during this period within elite soccer (Nedelec et al., 2013). The aim of this thesis was to understand the activities undertaken by elite soccer players during the recovery period following match play and to investigate the suitability of the various approaches to monitor physiological status during the period. The aim of study 1 (Chapter 3) was to provide an overview of the activities undertaken by soccer players (n=53) during periods of the training week dedicated to recovery following match play. The findings of this study show that massage therapy accounted for the longest amount of time on matchday +1 (MD+1) (43min) and pitch based active recovery on matchday +2 (MD+2) (44min). Pool based active recovery was the most consistently completed method on MD+1 (64%) and pitch based active recovery on MD+2 (80%). These data may not only provide useful information on the recovery processes included in the training plans of elite soccer players but also give potential insights into the strategies that may be used to effectively monitor this recovery between games. The aim of study 2 (Chapter 4) was to determine if heart rate variability (HRV) obtained through a purpose built smartphone application measured on the first day (MD+1) and second day (MD+2) following match play can detect changes in the physical loads undertaken by elite soccer players (n=21). No significant relationships between any of the physical loading variables assessed in this study and smartphone derived HRV MD+1 or HRV MD+2 (natural logarithm of the square root of the mean squared differences of successive R-R intervals [Ln rMSSD]) were found. This suggests that measurements of HRV through the ‘ithlete’ method may not be suitable for use in monitoring physiological status following soccer match play. The aim of study 3 (Chapter 5) was to develop a reliable exercise protocol that could be used for calculation of heart rate recovery (HRR) and percentage of maximum heart rate reached (%MAXHRr) with elite soccer players (n=15) while adhering to the specific characteristics of an exercise test that would facilitate completion with an elite soccer team. The data presented in this study suggests that the most suitable exercise protocol with regards to the reliability of the heart rate (HR) response and adherence to the physical loads used during the recovery period with elite soccer players was 6x80m straight-line runs at 5m/s with an exercise: rest ratio of 16:14s. This protocol presented coefficient of variation (CV), standard error of measurement (SEM) and physical loading data that were superior to data associated with other similarly styled protocols considered throughout this study. The aim of study 4 (Chapter 6) was to assess the face validity of the HR response to the developed standardised exercise protocol (SEP) under controlled conditions following a high physical load simulated soccer training session (HSSTS) and a low physical load simulated soccer training session (LSSTS) (n=10). The findings of this study suggest that the HR response to the SEP was able to detect manipulated changes in physiological status as a result of a high physical load and a low physical load simulated soccer training session. The %MAXHR during the SEP was found to be significantly higher following the HSSTS (92%) in comparison to the LSSTS (90%). HRR was found to be lower following the HSSTS (17%) when compared to the LSSTS (22%). The aim of study 5 (chapter 7) was to assess the effectiveness of using HRR and %MAXHRr measured through the SEP on the first day (MD+1), second day (MD+2), and third day (MD+3) following match play to detect changes in physical loads experienced by players (n=16) during the preceding soccer game. The findings of this study show the SEP to have limited capabilities in the detection of changes in HRR and %MAXHR on MD+1, MD+2, or MD+3. The data presented may suggest that the SEP is most suited for implementation on MD+2 or MD+3. It seems that HRR is the more sensitive of the markers investigated. In summary, the studies undertaken as part of this thesis provided an insight into the structure of the activities employed during the recovery period following elite soccer match play and the potential opportunities to monitor physiological status during this process. Initially this involved providing an understanding of the types of activities that were completed by players during this period. This was followed by an assessment of one of the current methods of monitoring physiological status (HRV analysis in chapter 4) during this time frame. This provided the basis for a novel method to be developed. The latter studies then focussed on developing a reliable and valid method of monitoring that could be easily implemented into the schedules during the recovery period within an elite soccer club which were outlined at the outset.
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