|
Murray, NP and Raedeke, TD. International Journal of Sports Psychology, 2008; 39: 346-355
Background
Most athletes are familiar with, and have experienced, sweaty palms and a pounding heart in the lead up to an important event. These feelings are an example of what sport psychologists term arousal. Competitors need a certain level of arousal to perform but over arousal can be just as detrimental to performance as a lack of arousal. Major championships are littered with performers who ‘choke' on the occasion - this is often a case of arousal levels getting the better of them.
An important role of a sport psychologist is managing arousal levels prior to and during performance. Elevated arousal is a strong component of anxiety and can lead to muscle tension, loss of focus and ultimately a reduced level of performance. Existing techniques for measuring arousal fall broadly into two groups; lab based methods which are impractical for use in the field or ‘paper-pencil' measures (e.g. questionnaires) which tend not to show moment to moment changes in arousal. A better measurement technique is needed if a coach or researcher is to gain a better understanding of pre-competition arousal and how to manage it.
|
Heart Rate Variability (HRV)
An athlete with a heart rate of 60bpm will have on average 1s between each contraction of the heart. In reality the time gap between contractions is not constant and sometimes may be slightly shorter or longer. HRV is a measure of this variability in time between heart beats. For more information see the Factsheet on HRV in the PBscience library
|
|
Heart Rate Variability (HRV) has seen a dramatic rise in interest recently. HRV was previously only measurable in the lab with the use of an ECG machine and so had limited practical applications. However companies such as Polar have incorporated HRV measurements into some of their HR monitors, opening the door to athletes to use HRV as tool in monitoring their performance.
Methodology
20 participants from a large American University took part in two trials of a simple golf putting task. One trial was performed with just the researcher present (Control) while the other was performed in front of 35 other students (Experimental). The 20 participants (11 male, 9 female) had a mean age of 20.3 years and standard deviation of 2.3 years. All were fit and healthy but had little or no golfing experience. Participants completed the Competitive State Anxiety Inventory-2R (CSAI-2R) to measure arousal levels before each trial, then HRV was measured for 5 minutes while seated. Performance in each trial was measured as the number of 8ft putts made out of ten attempts.
|
When studying HRV it is useful to look at both time and frequency changes in HR. The following are important aspects to measure
Standard Deviation of normal to normal intervals (SDNN) - this is a measure of the variation in time between successive QRS complexes in an ECG trace, effectively the time between heart beats.
Low Frequency (LF) - a measure of the sympathetic or ‘accelerator' drivers of heart rate
High Frequency (HF) - a measure of the parasympathetic or ‘braking' drivers of HR
For optimal performance it is believed that both LF and HF should be relatively high but also well matched, as shown by a LF/HF ratio close to 1
|
Results
Figure 1 shows that HRV was lower in the Experimental trial, as shown by a decrease in SDNN, whereas both cognitive and somatic anxiety, as measured by the arousal questionnaire, were noticeably increased. There was also a significant increase in LF power and decrease in HF power, hence an increase in average LF/HF ratio from 1.05 to 5.67 between the Control and Experimental trials. Subjects averaged 7.6 successful putts in the Control trial compared with 3.55 in the Experimental trial.
|
Summary
In the experimental trial the mean values of anxiety were significantly increased, while HRV and performance were significantly decreased.
|
What does this mean?
In practise the use of HRV as a measure of pre-competition arousal is likely to be fraught with complications. There are so many other factors that can affect an athlete's HRV; e.g. temperature, fatigue, body position etc that it will be difficult to attribute changes in HRV to arousal levels in particular. The current study measured HRV during a five minute seated period - it might prove challenging to fit this around an existing warm up routine and again the warm up protocol will have an effect on HRV. This application of HRV does initially sound appealing but more research is needed, particularly into an individual's changes in HRV from day to day, and in practice the coach would need a collection of historical HRV data to put into context any pre-competition measure of HRV.
|
