← Performance & Longevity // tracking · hrv · bloodwork · data over guessing

What I track —
and what it has
taught me.

I like data. Not because numbers are the point — but because they reveal things that intuition alone cannot. The most useful thing tracking has taught me is that my assumptions about my own recovery, sleep quality, and health were often wrong. My vitamin D was almost low despite living in Florida. That single data point is why I check labs. You cannot manage what you do not measure.

// why track at all

Data over guessing —
the case for measuring yourself.

Physicians are trained to be skeptical of n=1 data. A single patient's self-report is not evidence. Wearable data is not a clinical measurement. And yet — the alternative to tracking your own health metrics is guessing. And guessing, as it turns out, is surprisingly unreliable even for people who pay close attention.

I thought I was sleeping adequately. The data showed otherwise — deep sleep was consistently lower than I expected, and the nights I felt most rested did not always correspond to the nights the numbers looked best. I thought I was recovering well after hard weeks. The HRV trend told a different story. I thought living in Florida meant my vitamin D was fine. It was almost deficient.

None of these findings required clinical intervention. But all of them changed my behavior. That is the value of tracking at the personal level — not diagnosis, not treatment, but signal. The data points toward things worth paying attention to before they become problems.

I am also aware of the limits. A consumer wearable is not a medical device. HRV measured on an Apple Watch is not equivalent to clinical HRV measurement with validated electrodes. Sleep staging from an accelerometer is an estimate. The number I see in the morning is a proxy for the underlying physiology — useful for trends over weeks and months, not definitive for any single night. I use it as signal, not verdict.

“My vitamin D was almost low despite living in Florida year-round. That was the specific data point that convinced me that lifestyle assumptions are not a substitute for actual measurement.”

// daily wearable tracking

Apple Watch —
four metrics, every night.

All four tracked automatically. No manual input required beyond wearing the watch to sleep. The value is in the trend line over weeks and months — not any individual data point.

HRV
Heart Rate Variability
The metric I watch most closely. HRV measures the variation in time between heartbeats — a higher number generally reflects a well-recovered nervous system; a lower number suggests accumulated stress, inadequate sleep, or overtraining. When my HRV trends down over several days, something is wrong — usually sleep, stress, or both. I have adjusted training and schedule decisions based on what this number shows over time.
// trend over weeks > any single night
RHR
Resting Heart Rate
Simple, reliable, and underrated. Resting heart rate is one of the clearest markers of cardiovascular fitness and recovery status available from a consumer device. If mine trends upward over a week without a change in training load, the signal is usually inadequate sleep or elevated stress. It moves slowly enough to be meaningful without the day-to-day noise of HRV.
// directional change is the signal
SLEEP
Sleep Duration & Stages
Total sleep time, deep sleep, and REM tracked automatically. The data showed me I was consistently getting less deep sleep than I thought — and that the nights I felt most rested did not always align with the nights the numbers looked best. Target is 7–8 hours. The data has made me take this target more seriously than I otherwise would.
// 7–8 hr target · quality matters
ACT
Activity & Steps
Daily steps and active calories. Less informative than HRV or sleep for recovery purposes — but useful as a consistency check. On clinic and OR days with no dedicated workout, steps accumulated through walking between cases, to and from parking, and incidental movement add up more than expected. Movement during work counts.
// consistency check · incidental movement matters
// a note on wearable accuracy

The Apple Watch is not a medical device. HRV measured on a consumer wearable uses optical sensors at the wrist rather than clinical-grade ECG electrodes — the absolute numbers are not directly comparable to clinical HRV measurements. Sleep staging from an accelerometer is an estimate, not a polysomnography. What wearables do well is track relative change in an individual over time. My HRV trending from 65 to 45 over two weeks is a meaningful signal even if neither number is clinically precise. Use the trend. Do not over-interpret any single data point.

// active experiment

Food tracking —
two tools, two different questions.

I track food in two distinct ways. A calorie logging app answers the question of how much I am eating. Yuka answers the question of what is actually in it. Neither replaces the other and they serve completely different purposes.

// 01 · calorie tracking · how much
Calorie logging — getting an accurate picture of intake.

Calorie intake is easy to underestimate — significantly. On busy OR days I skip meals and eat opportunistically, which means calories land in a compressed window. On stressful days the binge eating pattern kicks in. In both cases, my intuitive sense of how much I have eaten is unreliable.

The data from the brief periods I have tracked consistently confirms this. The gap between what I thought I was eating and what I was actually eating was larger than expected. Consistently in one direction. Tracking makes that gap visible.

I am trialing calorie logging apps to find one that works on busy surgical days. Calories only — not macros, not meal timing. Get the baseline right first.

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Calories only — not macros, not meal timing
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Trialing apps — testing what is sustainable on surgical days
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Still working on consistency — the habit, not the technology
// 02 · ingredient scanning · what
Yuka — scanning what is actually in things.

I use Yuka to scan packaged foods and supplements. Point the camera at a barcode and it pulls the ingredient list, flags additives, scores the product for ingredient quality, and identifies anything worth paying attention to.

Yuka is not perfect — its algorithm is not always consistent with peer-reviewed science. I use it as a quick filter, not a definitive verdict. The scan starts the conversation with the label. It does not end it.

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Packaged foods — additives, artificial ingredients, synthetic dyes
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Supplements — proprietary blends, unlisted fillers, ingredient conflicts
▸
Overall quality — whole-food ingredients vs. processed fillers at a glance
// why calories only — for now

Adding complexity before the habit is established increases the likelihood of abandoning it entirely. The most important tracking is the tracking that actually happens. Protein is handled through food choices — eggs, chicken, lean meat. The calorie number is what I am trying to make visible and accurate first. I will update this page when I have settled on an approach that works consistently.

// periodic bloodwork

Labs every few years —
what I test and why.

I get comprehensive bloodwork done periodically — not on a fixed annual schedule, but every few years or when something prompts a closer look. The goal is not to optimize every number. It is to catch things that lifestyle assumptions might be masking. The vitamin D finding is the clearest example of why this matters.

// frequency: every few years · not on a fixed annual schedule
// why I don't list normal ranges or my values

Lab reference ranges vary by laboratory, age, sex, and clinical context. A number that is flagged as low by one lab's reference range may be entirely appropriate for another individual. More importantly, interpreting bloodwork requires clinical context that a number on a page cannot provide. If you are interested in getting your own labs done, the right person to interpret them is your physician — not a webpage. What I can offer is the reasoning behind why each panel is worth checking periodically for an active, health-focused adult.

CBC
Complete Blood Count
Red cells, white cells, platelets, hemoglobin, hematocrit
+
The foundational panel. A CBC gives a broad picture of overall health and can flag anemia, infection, immune dysfunction, and clotting abnormalities — most of which are asymptomatic in their early stages. For an active person who trains consistently, mild anemia is easy to miss because fatigue and reduced performance are attributed to training load rather than insufficient red cell mass. A CBC catches it.
MarkerWhy it matters for active adults
Hemoglobin / HematocritOxygen-carrying capacity. Directly affects exercise performance, recovery, and fatigue. Anemia can be subtle and long-undetected.
WBC differentialChronic low-grade immune activation or suppression. Useful baseline for someone managing high physical and cognitive stress loads.
PlateletsClotting function. Relevant for anyone considering antiplatelet supplements (fish oil, aspirin, garlic at high doses).
MCV / MCHRed cell size and hemoglobin content — can indicate iron or B12/folate deficiency before hemoglobin drops.
CMP
Comprehensive Metabolic Panel
Glucose, electrolytes, kidney function, liver enzymes (LFTs)
+
The CMP is the broadest single panel available — covering kidney function, liver health, blood glucose, electrolyte balance, and protein status simultaneously. For someone taking supplements including high-dose B vitamins, creatine, and herbal compounds, periodic liver enzyme checks are a reasonable baseline. Creatinine and BUN reflect kidney function and are relevant for anyone consuming high protein and creatine long-term. Glucose is the early screen for insulin resistance before A1c becomes abnormal.
MarkerWhy it matters for active adults
AST / ALT / GGT (LFTs)Liver enzyme elevation can occur with high-dose supplements, statins, alcohol, or underlying liver pathology. Baseline is useful for anyone taking a supplement stack.
Creatinine / BUNKidney function. Creatinine supplementation modestly raises serum creatinine — knowing your baseline matters for interpretation. High protein intake also raises BUN.
Fasting glucoseEarly insulin resistance marker. Fasting glucose can be elevated for years before diabetes develops. Lifestyle intervention works best early.
Electrolytes (Na, K, Cl, CO2)Sodium, potassium, and bicarbonate balance — relevant for anyone who trains hard, sweats significantly, or uses a sauna regularly.
Albumin / Total proteinNutritional status and liver synthetic function. Low albumin in an otherwise healthy active adult can indicate inadequate protein intake.
Mg
Magnesium
Serum magnesium — one of the most commonly deficient minerals
+
Magnesium is involved in over 300 enzymatic reactions — including energy production, muscle contraction, nerve conduction, and sleep regulation. Deficiency is extremely common in the general population and is frequently asymptomatic until it is not. Active adults who sweat regularly lose magnesium through sweat; those who use saunas frequently compound this. Serum magnesium is an imperfect measure (most magnesium is intracellular) but is the most practical available outside of research settings. I supplement magnesium through my multivitamin — checking the serum level tells me whether that is sufficient.
MarkerWhy it matters for active adults
Serum MgProxy for magnesium status. Affected by heavy sweating, sauna use, high caffeine intake, and GI absorption. Low magnesium affects sleep quality, muscle recovery, and energy metabolism.
Phos
Phosphorus
Bone health, energy metabolism, cellular function
+
Phosphorus is the second most abundant mineral in the body after calcium, and is essential for bone mineralization, ATP production, and cell membrane integrity. Abnormal phosphorus levels are less common than magnesium deficiency in otherwise healthy adults, but checking it periodically provides a useful picture of bone mineral metabolism — particularly relevant when calcium and vitamin D status are also being assessed. Phosphorus and calcium metabolism are tightly linked, and abnormalities in one can affect the other.
MarkerWhy it matters for active adults
Serum phosphorusBone mineral metabolism alongside calcium and vitamin D. Low phosphorus can indicate malabsorption or inadequate intake; elevated levels can reflect kidney dysfunction.
T
Testosterone
Total and free testosterone — muscle, energy, mood, cognitive function
+
Testosterone declines with age in men at approximately 1–2% per year after 30. The decline is gradual enough that many men attribute the downstream effects — reduced muscle mass, lower energy, decreased libido, changes in mood and cognitive sharpness — to aging itself rather than to a measurable hormonal change. Checking it periodically establishes a personal baseline and makes any significant decline detectable before it becomes symptomatic enough to affect quality of life or surgical performance. Free testosterone (the biologically active fraction) matters as much as total — SHBG elevation with age means total testosterone can be in range while free testosterone is meaningfully low.
MarkerWhy it matters for active adults
Total testosteroneOverall androgen status. Affected by sleep quality, body composition, stress, and training load — all of which are tracked independently.
Free testosteroneThe biologically active fraction. More informative than total testosterone alone, particularly in older men with elevated SHBG.
SHBGSex hormone binding globulin — determines what fraction of total testosterone is free and active. Increases with age.
TSH
Thyroid Function
TSH — the primary screen for thyroid dysfunction
+
Thyroid dysfunction — both hypothyroidism and hyperthyroidism — is common, frequently asymptomatic in early stages, and has a significant impact on energy, metabolism, weight, heart rate, mood, and cognitive function. TSH is the most sensitive screening test for thyroid disorders. The symptoms of subclinical hypothyroidism in particular (fatigue, weight gain, cold intolerance, slow recovery) overlap significantly with overtraining and inadequate sleep — making it easy to attribute to lifestyle factors when the cause is actually hormonal. A periodic TSH rules out the thyroid as a variable.
MarkerWhy it matters for active adults
TSHPrimary thyroid screen. Elevated TSH signals hypothyroidism; suppressed TSH signals hyperthyroidism. Symptoms of both mimic common lifestyle complaints.
Free T4 / Free T3 (if TSH abnormal)More detailed thyroid assessment when TSH is out of range. Not routinely checked when TSH is normal.
B12
Vitamin B12
Neurological function, red cell production, DNA synthesis
+
B12 deficiency is more common than widely appreciated, particularly in people who take proton pump inhibitors (PPIs), metformin, or who have reduced gastric acid production with age. Neurological symptoms of B12 deficiency — peripheral neuropathy, cognitive changes, fatigue — can develop before anemia appears and can be irreversible if uncorrected for long enough. As a neurosurgeon who sees peripheral nerve pathology regularly, checking B12 periodically is straightforward due diligence. I supplement methylcobalamin through my multivitamin — the serum level confirms whether absorption is adequate.
MarkerWhy it matters for active adults
Serum B12Neurological function, cognitive performance, red cell synthesis. Deficiency develops slowly and can cause irreversible neurological damage if missed.
B9
Folate
DNA synthesis, homocysteine metabolism, red cell production
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Folate works closely with B12 in DNA synthesis and homocysteine metabolism. Elevated homocysteine — which occurs with folate or B12 deficiency — is associated with cardiovascular risk and neurological dysfunction. Folate deficiency causes megaloblastic anemia and can mask B12 deficiency if folate is repleted without also addressing B12. I take methylfolate (the active form) through my multivitamin — checking the serum level confirms adequacy, particularly given the high prevalence of MTHFR variants that impair conversion of folic acid to the active form.
MarkerWhy it matters for active adults
Serum folateDNA synthesis and homocysteine regulation. Interacts closely with B12 — both should be checked together.
Homocysteine (if low folate/B12)Elevated homocysteine is an independent cardiovascular and neurological risk factor — a downstream consequence of inadequate B12 or folate.
A1c
Hemoglobin A1c
3-month average blood glucose — the best screen for pre-diabetes
+
A1c reflects average blood glucose over the preceding 2–3 months, making it a more informative screen for insulin resistance and pre-diabetes than a single fasting glucose measurement. Pre-diabetes affects an estimated 1 in 3 American adults — the majority of whom are undiagnosed. The condition is asymptomatic in its early stages and entirely reversible with lifestyle intervention, but progresses to type 2 diabetes without intervention. Body composition, dietary patterns, sleep quality, and exercise frequency all affect A1c — all of which I track independently. The A1c tells me whether those habits are producing the metabolic outcome they should.
MarkerWhy it matters for active adults
HbA1c3-month glucose average. More reliable than fasting glucose for detecting early insulin resistance. Pre-diabetes is asymptomatic and reversible — if caught early.
ESR
Erythrocyte Sedimentation Rate
Non-specific marker of systemic inflammation
+
ESR is a non-specific inflammatory marker — it does not identify the source or cause of inflammation, but an elevated level signals that something in the body is driving an inflammatory response. It is a useful screening tool for occult infection, autoimmune disease, malignancy, and chronic inflammatory conditions, many of which are asymptomatic in early stages. As a surgeon who operates on patients with spinal infections, inflammatory spondyloarthropathies, and inflammatory spinal conditions, I have a particular appreciation for catching systemic inflammation early. In a healthy, active adult with no symptoms, a normal ESR is reassuring. An elevated one warrants further investigation.
MarkerWhy it matters for active adults
ESRBroad inflammatory screen. Non-specific but sensitive. Elevation in an asymptomatic person warrants further workup for infection, autoimmune disease, or occult malignancy.
CRP (often checked alongside)C-reactive protein — a more specific and rapidly responding inflammatory marker than ESR. Together they provide a fuller picture of systemic inflammatory status.
LP
Lipid Panel
Total cholesterol, LDL, HDL, triglycerides — cardiovascular risk profile
+
The lipid panel is one of the most well-validated cardiovascular risk screens available. LDL cholesterol, particularly LDL particle number and small dense LDL, is one of the strongest modifiable predictors of atherosclerotic cardiovascular disease. Triglycerides reflect dietary carbohydrate and alcohol intake and are highly responsive to lifestyle change. HDL — the so-called protective cholesterol — reflects reverse cholesterol transport and is elevated by regular aerobic exercise and reduced by sedentary behavior and trans fats. A complete lipid panel, ideally with LDL particle number or apolipoprotein B for greater precision, gives a meaningful picture of cardiovascular risk that basic vitals and symptoms cannot.
MarkerWhy it matters for active adults
LDL cholesterolPrimary atherogenic lipoprotein. Standard LDL-C is an estimate — LDL-P (particle number) or ApoB are more precise for risk stratification.
HDL cholesterolCardioprotective. Raised by regular aerobic exercise. Low HDL is an independent cardiovascular risk factor.
TriglyceridesHighly responsive to diet and lifestyle. Elevated triglycerides with low HDL is the classic insulin resistance lipid pattern.
Total cholesterol / TC:HDL ratioBroad cardiovascular risk index. Less informative than LDL-P or ApoB but widely reported and useful for trend tracking.
ApoB (if available)Counts all atherogenic particles directly — more precise than calculated LDL-C for cardiovascular risk stratification.
D
Vitamin D (25-OH)
The one that proved assumptions wrong
+
This is the test that made me a believer in periodic bloodwork. I live in Florida. I am outdoors. I assumed my vitamin D was fine. It was almost deficient. The reasons are straightforward in retrospect — I spend the majority of daylight hours indoors, in operating rooms with no windows and no UV exposure, or in clinic. When I am outside it is often early morning or evening when UV-B is minimal. Sunscreen during outdoor activity further reduces synthesis. Modern indoor professional life in a sunny climate does not reliably produce adequate vitamin D. You have to check.
MarkerWhy it matters for active adults
25-OH Vitamin DThe storage form of vitamin D and the correct test to order for status assessment. Supports bone density, immune function, muscle performance, and mood. Deficiency is common even in sunny climates for people who spend most of the day indoors.
// the takeaway

Track the trend.
Check the labs.
Do not assume.

The vitamin D finding is the reason. You cannot manage what you do not measure — and you cannot measure what you do not test. If your spine is limiting what you can track, train, or do, that is worth addressing.

Request a Spine Consultation
The health tracking and bloodwork information on this page reflects Dr. Katsevman’s personal approach and is not medical advice. Lab values and their interpretation depend on individual clinical context. Consult your physician before ordering or interpreting laboratory tests. Wearable device data is not equivalent to clinical measurement and should not be used for medical decision-making.