Updated: Sep 23
Last evening it was squash (sport) and shower time with upBeat®. I decided to wear upBeat® while playing squash to monitor my body's physiological responses during this intense sport. Further, I also wore upBeat® while having shower to check its performance.
How hard can squash (sport) be?
Squash is played in a small square court, measuring just 32 feet from front to back and 21 feet across, and consists of hitting a ball against the 15-foot high front wall. When you see squash for the first time, you might think, "How hard can that be?" When you play it for the first time, and your lungs and thighs are burning after five minutes, you'll have your answer. The reason squash is so physically demanding is because it is played with a squishy ball that is hard to put away.
Data from Tarek Momen’s first-round match against Mathieu Castagnet at the Swedish Open earlier this year offers some insight – and an intriguing comparison with tennis. Momen won the 97-minute match but not before he had covered 5km on the court, struck the ball almost 1,000 times, contested 100 points and covered an average of 48 metres per point. Most of his movement consisted of three-six meter sprints, almost half of which were backwards. Momen spent over 60% of the match – more than an hour – in play.
Those numbers look even more impressive when compared with the longest match at Wimbledon last summer, Rafa Nadal’s epic five-set defeat to Gilles Müller. That match lasted 288 minutes, but Nadal only covered 3.645km, was only in play 15% of the match and only ran 9.4 metres per point. Put simply, Momen ran further in less time with less rest, while covering more distance per point. The data is not intended to decry either sport but to show the fascinating contrast in their physical demands.
Monitra's upBeat® Biosensors
upBeat® is a wearable medical grade biosensing skin patch that continuously 24x7 captures electrocardiogram (ECG) and tracks posture as well as activities in real-time. This physiological data is transmitted continuously to the phone and the information is relayed to our cloud platform, upBeat®.AI.
Play Time, Pre & Post too - Activity & Cardiac Performance
The baseline average heart rate is around 85 bpm prior to play starts. The warm up starts around 08.03 pm and thereafter the average heart rate steadily rises to about 170 bpm before the first break is taken around 08.25 pm. The average heart rate falls to about 130 bpm just before play resumes 3 mins later at 08.28 pm. The maximum average heart rate thereafter steadily rises to a level (190 bpm) higher than the maximum in the earlier play (170 bpm). At 8.42 pm, the play ends and thereafter the average heart rates falls steadily to about 95 bpm in 25 mins. The activity levels can be seen in the 3-axis accelerometer plot.
You will notice the activity levels rise during shower time. It'd be interesting to note the performance of upBeat® during shower which is illustrated later in the article.
Baseline ECG at 08.01 pm
The heart rate is about 90 bpm.
During Warmup at 08.08 pm
The heart rate is about 120 bpm. Notice the shift in QRS morphology.
During mid-game at 08.16 pm
The heart rate is about 150 bpm. Notice the T and p waves.
Artifact during intense play at 08.17 pm
The heart rate is about 150 bpm. Notice the artifact which occurred while reaching out for the squash ball during an intense rally.
Ventricular beat during the first break at 08.20 pm
The heart rate is falling down and is now about 140 bpm. Notice the ventricular beat in the plot below.
ECG during intense play just before the game ends.
08.40 pm 05 seconds
The heart rate has raced to about 180 bpm. Notice the artifacts which increases in the beginning and recovers subsequently towards the end of the plot.
08.41 pm 25 seconds
The heart rate is about 190 bpm. Notice the artifacts during play.
08.41 pm 33 seconds - Game ends
The heart rate is about 200 bpm. Notice the artifacts go away instantaneously once the game ends.
ECG during recovery at 08.55 pm - 14 mins after the game ends
The heart rate is about 130 bpm. Notice the artifacts go away and also the QRS amplitude has reduced.
ECG prior to shower at 09.30 pm
The heart rate is about 110 bpm. Notice the QRS amplitude has reduced further.
ECG during shower
Please note that it was light warm shower with water flowing onto the device. However, care was taken to ensure that the shower jets don't directly fall on the device. This version is not designed to be water resistant.
08.34 pm 35 seconds
The heart rate is about 120 bpm. Notice some artifacts and the ECG recovers.
08.37 pm 35 seconds
The heart rate is about 110 bpm.
ECG at midnight at 12.00 am
The heart rate is about 80 bpm. Notice that the QRS amplitude and morphology has completely recovered. See the baseline ECG at 08.01 pm above.
QRS amplitudes [Edit: Added on Dec 07, 2018]
The amplitude of the QRS signals reduces after exercise and recovers completely in due course.
08.01 pm - Before play
08.16 pm - Mid-game
08.55 pm - Recovery after game
12.00 mid-night (Amplitudes similar to the one at 08.01 pm before play)
Ventricular beats [Edit: Added on Dec 07, 2018]
It was observed that the ventricular beats were detected during play, almost doubled in the immediate post-exercise period (one hour after play) and reduced thereafter. The findings are similar to ones in reference 5.
Some thoughts [Edit: Dec 07, 2018]
Squash is a physiologically demanding sport which places a severe strain on the heart muscle for considerable periods of time with the body being subjected to sudden and vigorous demands.
Artifacts like signals seen in ECG during peak exercise <maximum cardiac performance> and the signals recover immediately to resemble normal ECG instantaneously. Similar signals were observed on the athlete during the 10K event. Check the article here.
The more pertinent question to investigate is whether heart rate a good enough metric or better understanding of ECG cardiac cycle morphology can lead to a better metric to optimize cardiovascular training programs in fitness and competitive sports leading to better outcomes.
Northcote RJ, MacFarlane P, Ballantyne D. Ambulatory electrocardiography in squash players. Br Heart J. 1983;50(4):372-7.