Folkard (1985)

• However opposing research by Folkard (1985) set participants sleep and wake times that initially fit with a 24-hour day, but then unknown to the participants, he sped up the clock so the cycle only lasted 22 hours. This had a significant impact on the participants who were adversely affected by the change from the set 24-25 hours. Only one participant easily adjusted to the shortened day. This suggests the strength of the body’s sleep/wake cycle, as it resisted environmental changes.
• We know that higher body temperatures during sleep are linked to a lower amount of deep sleep, both NREM and REM sleep, and this can have a noticeable effect on how you feel when you wake up. The body cools as you enter NREM and heats up slightly when you enter REM. REM sleep is important for recovery and repair of your muscles and tissues. If you’ve ever gone to bed aching after a tiring day, deep sleep is what helps you to feel recovered the next morning.
• Endogenous pacemakers (EP’s) are internal mechanisms that govern biological rhythms, in particular, the circadian sleep-wake cycle. Although endogenous pacemakers are. internal biological clocks, they can be altered and affected by the environment.
• Exogenous zeitgebers (EZ’s) are social cues, such as meal times and social activities, but the most important zeitgeber is light, which is responsible for resetting the body clock each day, keeping it on a 24-hour cycle.
• studied a group of 12 people who agreed to live in a dark cave for 3 weeks, retiring to bed when the clock said 11:45pm and rising when it said 7:45am
• over the course of the study, the researchers gradually sped up the clock without participants knowing so an apparent 24 hour day now only lasted 22 hours
• it was revealed that only one of the participants were able to adjust comfortably to the new regime
• this would suggest the existence of a strong free-running circadian rhythm that cannot easily be overridden by changes in the external environment