Fig. 4: Volunteer testing with the WARM system for continuous penile erection assessments.

a Procedure for the AVSS test using both the RigiScan and the WARM system as penile erection monitoring tools. b Comparison of tumescence and rigidity measurements between the two systems during the AVSS test. c Procedure for the NPTR test: Sleep was monitored for three consecutive nights, followed by a synchronized NPTR-sleep test on one night. d Sleep stage data for four consecutive nights as recorded by Fitbit. Sleep stages are categorized into deep sleep, light sleep, rapid eye movement (REM), and awake periods. During the fourth night, both the Fitbit and WARM systems were worn simultaneously for the NPTR test. The proportions of deep sleep and REM sleep observed were not significantly different from those of the previous three nights. e Sleep stages and penile tumescence and rigidity data during the fourth night. Regions where the penile circumference increased by more than 6 mm or where rigidity exceeded 60% are highlighted in red. On the one hand, the close relationship between nocturnal erection and REM was verified; on the other hand, the reliability of the WARM system was confirmed