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STILL IN MOTION
Because slowing down isn’t in the plan.
THIS WEEK'S STORY
Issue #3 of this newsletter was about sleep. I told you that you can’t out-train bad sleep, that sleep is a performance enhancer, and that after 60 it becomes foundational. All of that is true.
But that issue told you the what without telling you the why — and the why is where the useful stuff lives.
Sleep is not a uniform state. A seven-hour night is not seven hours of unconsciousness. It is a cycling sequence of distinct neurological stages, each doing different work. And after 60, the specific stage most critical for physical recovery — slow-wave sleep, also called deep sleep or N3 — begins to deteriorate.
This means two people can sleep the same number of hours and have radically different recovery outcomes, depending on how much time each spends in deep sleep. Most people over 60 are spending significantly less time in deep sleep than they were at 40, often without knowing it.
Understanding what deep sleep is, why it declines, and what interventions actually affect it is where this issue lives.
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THE MAIN MESSAGE
Sleep occurs in 90-minute cycles, typically four to six per night. Three main stages:
N1 and N2 (light sleep):
The transition into sleep and the lighter sleep stages. Important for memory consolidation. Comprises roughly 50 to 60 percent of total sleep time.
N3 — Slow-Wave Sleep (deep sleep):
The most physically restorative stage. During N3, growth hormone is released (the primary signal for muscle repair and bone remodeling), the immune system performs repair work, inflammatory cytokines are cleared, and the glymphatic system flushes metabolic waste from the brain. Deep sleep is concentrated in the first half of the night.
REM sleep:
The dreaming stage, concentrated in the second half of the night. Critical for emotional regulation, procedural memory including motor patterns from training, and cognitive consolidation.
What happens to sleep architecture after 60:
- Deep sleep (N3) decreases significantly — from roughly 20 percent of total sleep time to 10 percent or less in many adults over 65. Growth hormone release, muscle repair, and inflammatory clearance that happen during N3 are compressed or curtailed.
- Sleep becomes more fragmented with more brief awakenings that disrupt the 90-minute cycle before completion.
- The circadian phase shifts earlier — older adults tend to feel sleepy earlier in the evening and wake earlier in the morning. This is a biological shift, not a character trait.
- REM sleep is disrupted by alcohol, certain medications, and sleep apnea — all more prevalent after 60.
What actually improves deep sleep after 60:
- Consistent sleep and wake times, including weekends. The circadian rhythm is the scaffold that determines when deep sleep occurs.
- Reducing alcohol, particularly within three hours of bedtime. Alcohol sedates but suppresses both REM and N3 architecture.
- Exercise — specifically resistance training and sustained aerobic work produce the largest documented increases in slow-wave sleep of any behavioral intervention.
- Cool sleeping environment: core body temperature must drop 1 to 2 degrees Fahrenheit to initiate deep sleep. Room temperature of 65 to 68 degrees Fahrenheit is optimal.
- Magnesium glycinate supplementation: a cofactor in GABA synthesis, most adults over 60 are deficient. 200 to 400 mg taken 30 to 60 minutes before bed is among the most consistently supported supplements for improving sleep depth.
Everything in this newsletter — the strength work, the mobility, the cardiovascular training, the bone density work — depends on deep sleep for its adaptation to occur. You are doing the training. Deep sleep is where training becomes fitness.
Stretch of the Week: Progressive Muscle Relaxation Sequence (Pre-Sleep)
Why: A structured, bottom-up muscle relaxation sequence reduces sympathetic nervous system activation and lowers core body temperature — two prerequisites for N3 sleep initiation. Takes 8 to 10 minutes in bed.
How to do it:
Lie on your back in bed, legs uncrossed, arms at sides
Starting with the feet: tense both feet firmly for 5 seconds, then release completely
Move upward: calves, thighs, glutes, abdomen, hands, forearms, upper arms, shoulders, face
Breathe slowly throughout — inhale before each tension, exhale during release
Let each release last 5 to 10 seconds before moving to the next muscle group
Total sequence: 8 to 10 minutes
Tuesday expands with three levels of pre-sleep relaxation practice, from two minutes to twelve, including a version with a gentle mobility addition for people whose physical tension is the primary barrier to sleep.
Strength Move of the Week: Supine Psoas March (Evening Activation)
Purpose: A gentle, low-demand core and hip flexor activation drill performed in the evening that maintains hip flexor and core tissue integrity without the sympathetic activation of a full training session. Helps transition the body toward the parasympathetic state needed for deep sleep.
How to do it:
Lie on your back, knees bent, feet flat on the floor
Breathe in diaphragmatically, then exhale and gently engage the core — lower back presses lightly into the floor
Slowly lift one foot off the floor, bringing the knee to 90 degrees above the hip — hold 3 seconds
Lower the foot slowly, then repeat on the other side
Alternate for 8 to 10 reps per side — slow, unhurried, breathing continuously
Thursday covers the training timing question: when to train relative to sleep, specific activities that help versus hurt sleep architecture, and two additional march variations.
Suggested Equipment: Sleep Tracking Device + Magnesium Glycinate
A sleep tracker (Oura Ring, Whoop, or a Garmin watch with sleep staging) provides objective data on deep sleep duration, REM sleep, and sleep continuity. Most people find their first week of data surprising. Paired with magnesium glycinate supplementation, these are the two highest-leverage sleep quality interventions outside of clinical sleep medicine.
Saturday covers the full sleep optimization toolkit: trackers, supplements, environment tools, and the one clinical conversation worth having if you have three or more specific symptoms.
SIM60 receives no commissions or affiliate compensation for any equipment referenced in this issue. All mentions are for illustration purposes only.
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THE TAKEAWAY
You cannot train your way to the adaptation that happens during deep sleep. You can only create the conditions for that sleep to occur. Consistent timing, cool temperature, no late alcohol, consistent training, and targeted magnesium supplementation are the behavioral levers with the most evidence behind them.
YOUR TURN
How is your sleep, actually? Not how long — how restorative. Do you wake feeling genuinely refreshed, or like the night was more endurance event than recovery? Reply and tell me. This matters more than almost any topic we cover.
Still moving forward,
— The SIM60 Team
simsixty.com · Educational content only. Not medical advice.
