Glossary

Active Recovery - is light physical activity (walking, yoga, stretching) on rest days to improve recovery. **How it manifests:

• ** - Improves blood circulation, helps eliminate metabolic waste - Helps to relax, reduces muscle stiffness - Should not be intense - the goal is not training, but recovery Active recovery is often more effective than complete rest for speeding up recovery after exertion.

Adaptation - is the process by which an organism adjusts to loads, becoming stronger and more resilient. **How it manifests:

• ** - It occurs during recovery after loads, not during training - It requires a balance between load and rest - It is disrupted by overtraining or insufficient recovery Adaptation - is the essence of the training process: load creates a stimulus, recovery allows for adaptation.

Alcohol and Sleep - alcohol can help you fall asleep, but significantly worsens sleep quality, especially in the second half of the night. **How it manifests:

• ** - Alcohol suppresses REM sleep, disrupts sleep structure - In the second half of the night, awakenings often occur - Recovery quality decreases, even if you slept for 8 hours Even a small amount of alcohol before sleep can negatively affect recovery.

Autonomic Balance - is the balance between the sympathetic (activity) and parasympathetic (recovery) nervous systems. **How it manifests:

• ** - Good balance: the body effectively switches between activity and recovery - Disruption of balance: constant activation of the sympathetic system leads to exhaustion - HRV often changes along with this balance It is easiest to think of this as a background: on calm days it is smoother, on overloaded days - “stricter”. Example: after a very busy week, the body may “hold” tension even in the morning, and then rest feels worse than usual.

Awakenings are short or long periods of wakefulness during nighttime sleep.

How it shows up: - 1-2 brief awakenings per night are common and often not remembered - Frequent or long awakenings disrupt sleep structure - Stress, alcohol, or noise often increase them

Short awakenings are normal, but frequent ones can reduce the feeling of rest.

Example: After a noisy night, a tracker often shows more awakenings and lower sleep efficiency.

Background fatigue is a sense of lower energy when there is no clear cause like a hard workout or a short night of sleep.

How it shows up:

• Less lightness even on calm days
• Heavier mornings than usual
• A feeling that the battery does not reach full

It is usually about the overall background: irregular timing, mental load, stress, and accumulated small factors.

Basal metabolism covers basic body functions at rest. It’s a base number, not the same as maintenance.

Blue Light is light with a wavelength around 400-500 nm, which affects melatonin and circadian rhythms.

How it shows up: - Device screens and LED lamps emit a lot of blue light - Evening exposure often delays sleepiness - It can shift sleep timing and reduce sleep quality

Blue light is useful during the day but can keep the body alert in the evening.

Example: After an hour on the phone before bed, falling asleep often takes longer.

Body Battery - is a concept that represents the body’s energy reserves as a battery that charges during rest and discharges during activity. **How it manifests:

• ** - Charges during sleep and rest - Discharges during physical activity, stress, illnesses - High level - good recovery, low - needs rest Body Battery helps visualize the balance between load and recovery throughout the day.

Caffeine Half-life is the time it takes for the body to eliminate half of the consumed caffeine. A common range is 3-5 hours.

How it shows up: - If you had coffee at 3:00 PM, by 6:00-8:00 PM half of the caffeine is still in the body - Caffeine can affect sleep quality even when alertness fades - The half-life varies across people

Many people notice that late caffeine shifts sleep later than expected.

Example: After an evening espresso, sleep can feel lighter even if you fall asleep on time.

A range absorbs normal daily variation and keeps recovery stable. It’s more realistic than one exact number.

Chronotype - is an individual predisposition to a certain time of activity and sleep, determined genetically and by circadian rhythms. **How it manifests:

• ** - “Larks”: wake up early, go to bed early, peak activity in the morning - “Owls”: wake up late, go to bed late, peak activity in the evening - Intermediate types: most people Understanding your chronotype helps optimize the sleep and activity schedule for better recovery and performance.

Circadian Rhythm is an approximately 24-hour cycle of physiological processes regulated by the body’s internal clock.

How it shows up: - Sets windows for sleepiness and alertness - Disrupted by time zone changes, night work, and irregular schedules - Affects energy levels and body temperature

A stable circadian rhythm usually makes sleep more consistent.

Example: After late shifts, falling asleep early can feel unusually hard.

A circadian rhythm is your body’s built-in 24-hour timing system. It helps coordinate daily patterns like feeling awake in the daytime and sleepy at night.

It’s strongly influenced by light and by regular habits such as when you wake up, eat, and wind down. When your circadian rhythm shifts earlier, you might start feeling sleepy earlier in the evening and wake up before your alarm even if you got enough sleep.

Cortisol - is a hormone produced by the adrenal glands in response to stress. It has a daily rhythm:

• high in the morning, low in the evening. How it manifests: - Normal rhythm: peak in the morning (helps to wake up), decrease in the evening (helps to fall asleep) - Rhythm disturbance: high cortisol in the evening interferes with falling asleep - Chronically high cortisol worsens recovery and sleep Cortisol balance is important for quality sleep and recovery - rhythm disturbance may indicate chronic stress.

Deep Sleep (slow sleep, stage N3) is the deepest phase of sleep, when the body focuses on physical recovery.

How it shows up: - Usually around 15-20% of total sleep time - More deep sleep happens in the first half of the night - This phase often feels like a full “power off”

When deep sleep is low, mornings can feel heavier.

Example: After a short night, deep sleep is usually lower than after a calm, long night.

Deficit is commonly used for weight loss. It should fit load and recovery; otherwise it feels too harsh.

Deload - is a planned period of reduced training load, usually by 40-60% of the usual volume. It is not complete rest or stopping training, but a strategic pause that allows the body to adapt to the accumulated load.

Deload is necessary because accumulated fatigue is not always immediately noticeable. After 3-4 weeks of intense training, the nervous system can become overloaded, even if you feel fine.

Deload provides time for recovery and often leads to improved results after returning to the usual load. Deload can be done as a preventive measure (every 4-6 weeks) or in response to signals: consistently low Recovery, a drop in HRV for several days in a row, subjective feelings of fatigue, decreased performance. Time frame: Usually, a deload lasts 5-7 days.

Less may not be enough for recovery, more may lead to detraining. Common mistake: People are afraid of “losing shape” and skip deload, trying to “tough it out.” The result is a forced break due to illness or injury, which lasts longer than the planned deload.

HRV (Heart Rate Variability) is the time difference between consecutive heartbeats. It is measured in milliseconds.

A simple way to think about HRV is as a background signal: is the body closer to tension or to relaxation right now. High HRV often goes with a calmer state.

Low HRV can show up with stress, poor sleep, fatigue, or alcohol the night before. It is not a diagnosis, just a signal.

HRV is very individual. For one person, a normal HRV may be 30 ms, for another - 90 ms. Trends matter more than absolute values.

Time frame: One low HRV day is often just a fluctuation. Several days in a row look more like a pattern.

Common mistake: Comparing your HRV to someone else’s and worrying that yours is low.

Example: If your usual number stays around the same level and then drops for a couple of days, it often reflects the general background rather than a single issue.

Insomnia is a pattern where falling asleep is hard, sleep is fragmented, or waking happens too early.

How it shows up: - Short-term insomnia often follows stressful events - Long-term insomnia feels like a steady pattern across weeks - It often shows up in sleep metrics, HRV, and readiness

In the tracker context, this is a description of a sleep pattern, not a diagnosis.

Example: Several nights in a row with long sleep onset and many awakenings often lead to lower sleep efficiency.

Jet Lag is a temporary disruption of sleep and circadian rhythms after a rapid change of time zones.

How it shows up: - Sleep and wake times feel shifted - Fatigue and lower focus are common - Some people use the “one day per time zone” rule, but it varies

Time and gradual adjustment are the most common ways people adapt.

Example: After a 3-hour shift forward, you may feel sleepy during the day and awake at night for a couple of days.

Load includes workouts, steps, and daily stress. It changes how a deficit feels and how quickly you recover.

Maintenance is a range, not one number. Daily energy use shifts with load and sleep, so a window is more realistic.

Recovery Compass shows a maintenance range based on your activity.

Melatonin is a hormone produced in response to darkness, which helps regulate circadian rhythms.

How it shows up: - It rises in the evening and helps the body feel sleepy - Light, especially bright blue light, suppresses it - It is often mentioned in the context of schedule shifts and jet lag, but it is not a universal “sleep button”

Melatonin is part of the sleep regulation system and helps signal that it is time to sleep.

Example: Bright light in the evening can delay the feeling of sleepiness.

Nap is a short sleep (often 10-30 minutes) during the day that can help with recovery and focus.

How it shows up: - A short nap (10-20 minutes) often boosts alertness - A long nap (over 30 minutes) can increase sleep inertia - Early afternoon is a common window for naps

Daytime naps can help in the moment but do not replace regular night sleep.

Example: A short nap can make the second half of the day feel easier.

NEAT (Non‑Exercise Activity Thermogenesis) often explains why the same calories work differently week to week.

Overreaching - is a condition when you train too intensely or frequently, not giving your body enough time to recover. **How it manifests:

• ** - Decreased performance despite training - Constant fatigue, irritability - Low recovery, HRV, and sleep quality indicators - Increased risk of injuries and illnesses Short-term overreaching can be part of the training process, but a chronic condition requires a reduction in load.

Overtraining - is a chronic state of overtraining that develops over weeks or months and requires a long recovery. **How it manifests:

• ** - Decreased performance despite rest - Constant fatigue, irritability, sleep problems - Low recovery metrics, HRV, increased RHR - It may take several weeks or months to recover Overtraining - is a serious condition that requires a significant reduction in load and a focus on recovery.

The parasympathetic nervous system is part of the autonomic nervous system. It is more active during rest and is associated with recovery.

In everyday life it can look like this: on calmer days it is easier to unwind in the evening, and in the morning you are more likely to wake up with a clearer sense of energy.

Typical signs:

• a shift toward rest and “settling” - lower heart rate - support for digestion and recovery processes

Higher HRV often goes together with stronger parasympathetic activity. The balance between sympathetic (activity) and parasympathetic (recovery) shapes the overall background.

Passive Recovery - is complete rest without physical activity:

• sleep, rest, relaxation. How it manifests: - Usually occurs during severe fatigue, during illness, or after injuries - Allows the body to fully focus on recovery - May be less effective than active recovery during moderate fatigue Passive recovery is important, but it should not be the only strategy - a balance with active recovery is usually optimal.

Periodization - is a structured approach to training planning that alternates periods of load, peak, and recovery. **How it manifests:

• ** - Includes microcycles (weeks), mesocycles (months), macrocycles (years) - Allows for planning deload weeks and recovery periods - Helps avoid overtraining and achieve peak performance Periodization helps optimize adaptation and avoid overtraining through the planning of load and recovery.

Plateaus often reflect adaptation and water shifts. Small adjustments and time usually work better than drastic cuts.

Re-entry effect means the short-lived slump some people notice when they switch from a break with little structure (like a vacation, time off, or a quiet period) back to a schedule with responsibilities.

It can feel like your energy and attention are lagging behind what your calendar expects. This isn’t about “doing it wrong” - it’s a common adjustment period as your brain and habits shift from flexible time back to deadlines, routines, and expectations.

Readiness is an integral metric that combines indicators like HRV, sleep, and RHR to describe the current background.

How it shows up: - High readiness often matches a steady sleep and a sense of energy - Low readiness is more common with fatigue, stress, or poor sleep - Trends matter more than one-off numbers

Readiness helps compare how you feel with the data and pick a pace without rushing.

Example: After a week of late nights, readiness can drop even if workouts were light.

Recovery is not just rest. It is a broader process of returning to baseline after physical and mental load.

In trackers, Recovery is usually an aggregated metric. It often includes HRV, resting heart rate, sleep, and recent load.

Because it is an interpretation, different trackers can show different numbers for the same day, and the same percentage can feel different depending on context.

Time frame: one low Recovery day after an intense day is common. Several days in a row usually describe a more stable background.

Common mistake: treating Recovery as a goal and starting to worry about the number itself.

Recovery is a tool for orientation, not a rating of your value.

Example: After a late dinner and a flight, Recovery can drop even without a workout.

Recovery includes sleep, rest, and sufficient energy. When it drops, even a moderate deficit feels much harder.

REM (Rapid Eye Movement) sleep is a phase when the brain is active and the body is mostly still. It usually accounts for 20-25% of total sleep time.

How it shows up: - Most REM sleep occurs in the second half of the night - Large shifts in REM often match a sense of lighter, less restorative sleep - Alcohol can reduce REM

REM sleep is often linked to memory and emotional processing.

Example: After a night with alcohol, sleep can be long but feel less restorative.

RHR (Resting Heart Rate) - is your pulse when you are completely relaxed, usually measured in the morning after waking up. **How it manifests:

• ** - Normal RHR for adults: 60-100 beats per minute - In trained individuals, RHR can be 40-60 beats per minute - Elevated RHR may indicate stress, illness, lack of sleep, or overtraining The trend is more important than absolute values: if your RHR is usually 55, and today it is 65 - this is a signal that something is wrong.

RMSSD - is one of the ways to measure HRV that focuses on the difference between consecutive intervals between heartbeats. **How it manifests:

• ** - High RMSSD usually indicates good recovery - Low RMSSD may indicate stress or overtraining - More sensitive to short-term changes than other HRV metrics RMSSD is often used in sports trackers to assess recovery and readiness for exercise.

SDNN - is a metric of HRV that shows the standard deviation of all intervals between heartbeats over the measurement period. **How it manifests:

• ** - High SDNN usually indicates good variability and recovery - Low SDNN may indicate stress, fatigue, or health issues - A more stable metric than RMSSD, better reflects long-term trends SDNN is often used in research as one way to describe overall heart rate variability. Example: if you are looking at your SDNN, it is more important to compare it with your usual level rather than with someone else’s numbers.

Sleep Apnea is a term used for breathing pauses during sleep that can repeat across the night.

How it shows up: - Frequent awakenings and loud snoring - Morning fatigue and daytime sleepiness - Often reflected in sleep and recovery metrics

In the tracker context, this term describes a possible sleep pattern, not a diagnosis.

Example: A person sleeps 8 hours but wakes up tired, with many awakenings and low sleep efficiency in the report.

Sleep Architecture is the pattern of alternating sleep phases (light sleep, deep sleep, REM) across the night.

How it shows up: - Typical cycles last about 90-120 minutes - Deep sleep is often heavier in the first half, REM in the second - Frequent awakenings can disrupt the pattern

Sleep structure matters alongside total hours.

Example: Two nights with 7 hours can feel different if one night had many awakenings.

Sleep debt is the gap between how much sleep usually feels normal for you and how much you actually got.

It tends to accumulate. If you sleep 6 hours instead of your usual 8, the difference adds up day after day.

When the debt grows, people often notice changes in focus, mood, and recovery, even if the day still looks fine on the surface.

Time frame: A small shortfall (for example, 1-2 hours) can feel easier after 1-2 nights of stable sleep. A longer period of short sleep usually takes longer to feel even again.

Common mistake: Assuming the body can be “trained” to need much less sleep. For most adults, the comfortable range stays relatively stable.

Example: A week of late nights can leave a lingering sense of fog even after a long weekend sleep.

Sleep Efficiency is the ratio of sleep time to total time spent in bed. In trackers, around 85% and above is often seen as good.

How it shows up: - If you spent 8 hours in bed but slept for 7, efficiency is about 87.5% - Low efficiency often comes with frequent awakenings - It can affect recovery more than just the number of hours

High sleep efficiency often feels better than a long night with many awakenings.

Example: Two people sleep 7 hours, but one wakes up often - their efficiency is lower and the morning feels harder.

Sleep fragmentation means you may get enough hours, but sleep feels less restorative because it is interrupted by awakenings and micro-awakenings.

In wearables it can show up as more awakenings and a less smooth night.

Example: you slept 8 hours but woke up many times, and it feels more like 6.

Sleep Hygiene is a set of habits and conditions that help sleep feel more stable.

How it shows up: - Similar sleep and wake times - A comfortable sleep environment (dark, cool, quiet) - Less stimulation and screens late in the evening - A calm wind-down routine

Sleep hygiene often affects recovery more than gadgets or supplements.

Example: When the schedule stays stable even on weekends, falling asleep is usually easier.

Sleep Inertia is a temporary state of drowsiness and sluggishness right after waking up.

How it shows up: - Usually lasts 15-30 minutes, sometimes longer - More noticeable when waking from deep sleep - Affects attention and reaction speed

Sleep inertia is common and varies from day to day.

Example: After sleeping in on the weekend, getting moving can feel slower than usual.

Sleep Latency is the time from when you lie down to when you fall asleep. A common reference range is about 10-20 minutes.

How it shows up: - Very fast sleep onset (under 5 minutes) often happens with sleep debt - Long sleep onset (over 30 minutes) can reflect stress or a busy mind - It affects total sleep time and efficiency

If sleep latency changes noticeably, it often reflects changes in fatigue or routine.

Example: After a long active day, sleep latency is often shorter than after a day at a desk.

Sleep Regularity Index (SRI) is a metric that estimates how consistent your sleep timing is from day to day.

Key idea:

• SRI usually improves when bedtime and wake time become more stable
• two people can both get “8 hours” while having very different regularity
• how you feel can be sensitive to stability, not only hours

Example: you sleep 8 hours, but on weekdays you sleep 11:30 pm to 7:30 am and on weekends you shift to 2 am to 10 am. Hours look similar, regularity is lower.

Social jet lag is not travel, but it can feel similar. Your body runs on one schedule, while your obligations force another.

A common pattern: early wake time on weekdays, sleeping in on weekends. Monday then feels like a time-zone shift.

Example: you wake at 11 am on weekends and 7 am on weekdays. The swing feels like mini jet lag.

Social jet lag is the gap between your weekday sleep timing and your weekend sleep timing. For example, you wake at 7:00 on workdays but drift to 10:00 on Saturday and Sunday.

That shift can feel like a small time-zone change even without travel. The term is often used to describe how school or work schedules shape sleep and how people feel day to day.

Strain (or Training Load) is a measure of accumulated load for the day. It shows how much cardiovascular work the body has done: intense workouts, long activity, many steps - all of that increases Strain.

High Strain does not equal a good workout, and low Strain does not equal a bad day. Strain reflects the fact of load but does not capture technique quality, strength, local muscle fatigue, or mental stress. It is one of the signals.

Strain helps describe adaptation: load → fatigue → recovery → progress. Without recovery, high Strain turns into wear, not growth. What matters is the balance between Strain and Recovery.

Time frame: One high Strain day after a workout is common. Several days in a row with high Strain and low Recovery often show accumulated fatigue.

Common mistake: Trying to “gain Strain” as a goal and ignoring context (heat, poor sleep, stress).

Example: A long walk and a busy day can produce noticeable Strain even without a workout.

Stress is a physiological and psychological reaction to changes or pressure. It can be mobilizing or draining depending on duration and context.

How it shows up: - Acute stress is short-term and often energizing - Chronic stress feels like ongoing tension - It often shows up in HRV, sleep quality, and recovery

Stress is not always bad by itself. The length and the background matter most.

Example: A tight deadline can sharpen focus for a day or two, but a month of the same pace usually lowers recovery.

Supercompensation - is the recovery phase when the body not only recovers to its initial level but also becomes stronger. **How it manifests:

• ** - It occurs after the correct balance of load and recovery - The peak of supercompensation - the optimal time for the next workout - If the peak is missed, adaptation is lost Supercompensation - is the goal of the training process: to become stronger through cycles of load and recovery.

Surplus is often used for gain or recovery from heavy load. It should remain moderate.

The sympathetic nervous system is part of the autonomic nervous system. It becomes more active during tension and “mobilization”: stress, load, strong emotions.

In everyday life it can look like this: after a conflict or a very busy day, the body stays in a more alert mode even at night, and sleep can feel less deep.

Typical signs:

• more readiness for action - higher heart rate - a shift toward a “stress” background if activation stays high for a long time

The parasympathetic system is the counterpart more associated with rest and recovery.

Taper - is the period of reducing training load before important competitions or events to achieve peak performance. **How it manifests:

• ** - Reduction of training volume by 40-60% while maintaining intensity - Usually lasts 1-3 weeks before the event - Allows for complete recovery and peak performance Taper helps achieve maximum performance by giving the body time for complete recovery and supercompensation.

On training days it often helps to stay near the top of the range and allocate extra calories to carbs.

VO2 Max - is the maximum volume of oxygen that the body can utilize during intense physical exertion. **How it manifests:

• ** - A high VO2 Max indicates good aerobic endurance - Improves with regular endurance training - Affects the ability to handle loads and recover VO2 Max - is an important indicator of physical fitness, but not the only factor influencing recovery and performance.