In the 1980’s, squash was booming in the UK. With this increase came an increase in sudden death fatalities related to the cardiovascular system.
In 1983 Northcote, MacFarlane and Ballantyne published a paper that looked into the reasoning behind such fatalities. In their subsequent paper, they assessed heart rate and rhythm changes by investigating the electrocardiographic events that occurred during and immediately after a game of squash.
Method – How the authors conducted the test.
The study consisted of 21 Male subjects selected from west of Scotland squash clubs. Subjects were graded to be of average standard and had played squash at least twice weekly for a minimum period of two years.
The mean age and body mass for the subjects were 33 ± 6.5 and 77.4 ± 8.65.
Prior to playing, subjects were fitted with an electrocardiographic monitor with electrodes placed on the manubrium sterni, in the fifth intercostal space and anterior axillary line of the chest wall on the left side of the chest. The electrodes were fastened in place with surgical tape to prevent them from falling off/giving an inaccurate reading.
Heart rate monitoring began 45 minutes before play. Prior to match play, a warm of 10minutes was given. Following the warmup subjects played for 40minutes. Monitoring continued throughout gameplay and was stopped 30minutes after gameplay had finished.
Mean heart rate was recorded on a minute by minute basis, before, during and after gameplay.
Results - what did the authors find.
Heart Rate Findings
The mean maximum heart rate was 170.28 ± 16.2 bpm. Expressed as a % of heart rate maximum, the heart rate was 90 ± 8.2 percent of the predicted heart rate max.
The mean heart rate during gameplay was 149 ± 17.8 bpm. Expressed as a % of heart rate maximum, the mean heart rate for the duration of the 40 minutes of gameplay was 80 ± 10.2 percent of the predicted heart rate max.
Authors noted rapid rise in heart rate in the first minutes of play as well as a commensurate drop off once gameplay finished.
Heart Rhythm Findings
The authors found that both premature ventricular contractions and premature atrial contractions occurred during and after play.
Premature ventricular contractions are “extra heartbeats that begin in one of the heart's two ventricles. Extra beats disrupt regular heart rhythm, sometimes causing a fluttering feeling or a skipped beat”.
Premature atrial contractions are a “common cardiac dysrhythmia characterised by premature heartbeats originating in the atria”.
Eight subjects developed at least one premature ventricular contraction, whilst only three subjects had more than five. Of the three subjects, two of them showed signs of ventricular tachycardia. No significant relationship was found between the age of the subject and the development of premature ventricular contractions. Within the 30 minutes post gameplay, seven subjects experienced at least one premature ventricular contraction. All but one of these subjects experienced premature ventricular contractions during gameplay. Only three subjects had five or more premature ventricular contractions post gameplay.
Ventricular Tachycardia is “an abnormal heart rhythm, or arrhythmia and occurs when the lower chamber of the heart beats too fast to pump well and the body doesn't receive enough oxygenated blood. In the paper the authors defined this as three or more premature ventricular contractions in succession at a rate of more than 100bpm”.
13 subjects developed at least one premature atrial contraction with only four having five or more premature atrial contractions during play. Post gameplay, six subjects experienced at least one premature atrial contraction; of the six subjects, only four of these subjects also experienced premature atrial contractions during play. Only one subject experienced heartbeat’s outside the normal rhythm prior to gameplay, though no evidence was found of this occurring during or after gameplay.
Conclusion:
Results show that squash places a prolonged and highly intense workload on the heart.
A rapid rise in heart rate occurs at the start of a squash game. In this study, the rapid rise in heart rate during gameplay was tempered by the 10-minute warm up. Not warming up could place individuals at increased risk of developing arrhythmia’s as heart rates could rise from resting 60-70bpm to more than 150bpm in a matter of minutes.
The authors noted that incidence of heart arrhythmia’s were higher than expected as none of the subjects showed evidence of cardiovascular disease. It was noted that such arrhythmia’s can occur with healthy individuals. One subject was advised against about his participation in squash due to the development of premature ventricular contractions and ventricular tachycardia over a long period of time as the development of such arrhythmia’s due to vigorous exercise is serious as it places one at risk of sudden death.
The authors did not provide a reasoning behind the development of the arrhythmia’s due to numerous possibilities (exercise intensity, myocardial ischemia - blood flow to heart blocked, asymptomatic coronary atherosclerosis, thermal stress, rise of catecholamines - adrenaline and hyperkalaemia), though noted that development during exercise may place individuals at increased risk of sudden death.
It was acknowledged that exercise is highly beneficial for cardiovascular health and plays a role in preventing coronary artery disease; though it was noted that there will always be a risk of sudden death when playing squash due to the vigorous nature of the game.
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Yours Truly,
Dominic Benacquista - Global Squash Coach
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Reference:
Northcote, R. J., MacFarlane, P., & Ballantyne, D. (1983). Ambulatory electrocardiography in squash players. British Heart Journal, 50(4), 372-377.