Kubalova, Z. et al. Modulation of cytosolic and intra-sarcoplasmic reticulum calcium waves by calsequestrin in rat cardiac myocytes. J. Physiol. 561, 515–524 (2004).

The Holter monitor records information about the heart’s electrical activity while the person goes about their normal activities for 1–2 days.

What are the different training zones?

Artificial light exposure at night can interfere with your circadian rhythm. Try to avoid using electronic devices that emit blue light - like phones and laptops - in the lead-up to bedtime. Keep naps short and early in the afternoon Skene, D. J. et al. Separation of circadian- and behavior-driven metabolite rhythms in humans provides a window on peripheral oscillators and metabolism. Proc. Natl Acad. Sci. USA 115, 7825–7830 (2018).

Unable to find the original French language version with English subtitles I was consigned to viewing the English dubbed version. While adequate I do wish I could have listened to the songs as they were written and the initially cast French actors. The music is lovely and moving and the English lyrics keep up. Flocus has other handy features, too — flip to Focus Mode to get in the groove with a Pomodoro timer and your custom focus priority, or put your feet up with calming spaces in Ambient Mode. Reitz, C. J. et al. SR9009 administered for one day after myocardial ischemia-reperfusion prevents heart failure in mice by targeting the cardiac inflammasome. Commun. Biol. 2, 1–15 (2019). Wehrens, S. M. T., Hampton, S. M., Finn, R. E. & Skene, D. J. Effect of total sleep deprivation on postprandial metabolic and insulin responses in shift workers and non-shift workers. J. Endocrinol. 206, 205–215 (2010). Centre for Biological Timing, Faculty of Biology, Medicine and Health, University of Manchester, Manchester, UKWeight Control (Fitness/Fat Burn): 60-70% of HR max. This is the best zone for burning fat. It gives you all the benefits of the moderate activity zone but with increased intensity. 85% of calories burned in this zone are from fat. Experimental design and n number determination were based on appropriate power analysis and previous experience. All ECG data were processed in MATLAB (R2018a; Mathworks, USA) using custom-written algorithms as described below. In both human studies, data were z-scored across the full laboratory session for each individual for analysis to normalize inter-individual variability. For mouse studies, data were z-scored across the whole analysis window (5 days for most analyses, ~9 days for phase shift experiments). Phase delays between RR and other ECG parameters were calculated by comparing the mean of a Gaussian fit to the cross correlogram in each individual to 0 using a one-sample T test. To calculate the dependency of ECG parameters on HR, change in z-scored RR between sequential 5 min ECG analysis windows were determined and segregated into bins reflecting response magnitude (width 0.25 SD in humans, 0.5 SD in mice). Corresponding changes in QT and PR seg were averaged and plotted against ΔRR interval. To determine the effects of locomotor activity on ECG parameters a circadian profile of each parameter at rest was calculated for each animal by fitting a 24-h constrained sine wave to all data points in which the animal had not been active in the preceding 30 min over 5 days of normal recording. Periods in which bouts of locomotor activity were followed by 45 min of inactivity were then isolated and normalized to the appropriate circadian phase based on the at-rest curve fit. The transient activity was identified as an activity bout preceded by >5 min of inactivity and followed by >20 min of inactivity. Data were normalized to the preceding 5 min of inactivity. RR interval distribution heatmaps were calculated by binning RR intervals of mice across 5 days of ECG recording into square bins of size 15 min × ~1.5 ms. Data were converted to a probability of an RR interval falling into any given bin within each 15 min window. Heatmaps were then filtered using a 5 SD Gaussian window with circular padding. Statistics and reproducibility A heart rate training zone is a range that defines the intensity of your training. The upper and lower boundaries of each zone are calculated using your maximum heart rate (HR max) which also depends on your age. Compensatory ion transport buffers daily protein rhythms to regulate osmotic balance and cellular physiology

Mice were implanted with telemetry devices (as above) and allowed to recover for 10 days post surgery. At ZT0 or ZT12 on the day of study, age-matched male mice were injected with 120 mg/kg caffeine (Fisher Scientific, USA) and 2 mg/kg adrenaline (Sigma, US) in PBS. Animals were monitored for 15 min before culling. Trains of at least four alternating ventricular premature complexes (characterized by a widening of QRS complexes and QRS inversion) were identified as bidirectional VT. In most cases, they lasted >30 s. Langendorff heart electrophysiology In control (non-shift-work) individuals, TSD and subsequent daytime recovery nap led to an expected and significant response in HR and RR interval during TSD and recovery nap, compared to equivalent times on the baseline day (Fig. 1B, D and Supplementary Fig. 2). QT interval is strongly influenced by HR, and as such mirrored the changes in RR (Fig. 1E and Supplementary Fig. 2). By contrast, PR seg duration (reflecting conduction through the AV node) was insensitive to the change in behavioral state, and followed a consistent 24 h profile across baseline and TSD days (Fig. 1F and Supplementary Fig. 2). While we have previously reported a small difference in RR variability (SDNN) following sleep deprivation 20, no differences in HRV were found between baseline and TSD days using a geometric measure 22 which is robust against changes in absolute HR (Fig. 1C). This suggests that time-of-day variation in parasympathetic tone (thought to be largely responsible for the circadian rhythm in HRV 6) was not disturbed by the change in arousal state. Thus, two critical aspects of cardiac conduction, SA node pacemaking, and AV nodal delay (reflected by RR and PR seg duration, respectively) exhibit clear and robust daily rhythms, yet are differentially responsive to altered sleep/wake and behavioral state. Given this temporal discordance, we next defined the interdependence of RR and PR seg measures over long (24 h) and short (5 min) time intervals (Fig. 1G–I). As expected, RR and QT interval profiles were closely aligned across the day. By contrast, the diurnal profile of PR seg was offset (phase delayed) from that of RR interval under normal (baseline) conditions (Fig. 1G), as confirmed by cross-correlation analyses (Fig. 1H). The relative insensitivity of PR seg to changes in RR was also evident over short timescales, where acute changes in RR interval between consecutive 5-min analytical bins were accompanied by a concordant change in QT interval, but not in PR seg (Fig. 1I). The insensitivity of PR seg duration to TSD and recovery nap, the phase offset between rhythms in RR and PR seg, and the insensitivity of PR seg to acute changes in RR were all similarly observed in the experienced shift workers (Supplementary Fig. 3). Together, these findings reveal a pronounced difference in the regulation of SA and AV nodal function and in their response to acute shifts in behavioral routine. We all want to know the secrets of ageing and how we might slow down age-related disease. Our heart function declines with age but this research has extraordinarily revealed that a variant of a gene that is commonly found in long-lived people can halt and even reverse ageing of the heart in mice. Unit of Clinical Physiology, Manchester Academic Health Science Centre, Faculty of Biology, Medicine and Health, University of Manchester, Manchester, UK Young, M., Razeghi, P., Cedars, A., Guthrie, P. & Taegtmeyer, H. Intrinsic diurnal variations in cardiac metabolism and contractile function. Circ. Res. 89, 1199–1208 (2001).

Zhang, J., Chatham, J. & Young, M. E. Circadian regulation of cardiac physiology: rhythms that keep the heart beating. Annu. Rev. Physiol. 82, 1–23 (2020). Wehrens, S. M. T., Hampton, S. M. & Skene, D. J. Heart rate variability and endothelial function after sleep deprivation and recovery sleep among male shift and non-shift workers. Scand. J. Work. Environ. Heal 38, 171–181 (2012).

Association of accelerometer-derived circadian abnormalities and genetic risk with incidence of atrial fibrillation This is still early stage research, but could one day provide a revolutionary way to treat people with heart failure and even stop the debilitating condition from developing in the first place.”

Further reading

Random sweeps from each individual were visually inspected for accuracy of automated feature detection and measurement. To validate the algorithm further, we compared automatically detected PR, QT, and RR intervals of a representative sweep from control individuals with manual measurements provided by an experienced cardiologist (LAV) of the average of that sweep and found no significant differences (Supplementary Fig S 1C). Professor Madeddu, Professor of Experimental Cardiovascular Medicine from Bristol Heart Institute at the University of Bristol said: