Endurance training after 45: what it gave you and what it can hide

The benefits are real

A 2023 scoping review of former athletes in midlife found that endurance athletes generally kept leaner bodies, higher maximal oxygen uptake and lower total cholesterol, triglycerides and glucose than comparison groups. Those advantages were strongest in people who were still active.

So if you are still logging miles at 50, that habit is protecting you in measurable ways. Nothing on this page is an argument for stopping. It is an argument for not letting good fitness talk you out of a few checks.

What the Master@Heart study found

The Master@Heart study used CT coronary angiography to compare 191 lifelong endurance athletes, 191 men who took up endurance sport after age 30, and 176 healthy non-athletes. All were men, with a median age of 55.

Lifelong athletes had higher odds of having at least one coronary plaque than non-athletes, including calcified, non-calcified and mixed plaque, and more plaque in the proximal parts of the arteries. The authors concluded that lifelong endurance sport was not associated with less coronary atherosclerosis.

This does not prove that endurance exercise causes heart disease, and it does not tell us how those plaques behave over time. Calcified plaque may be more stable than other types. What it does tell you is that fitness and arterial health are not the same measurement.

Why a standard cholesterol panel can mislead you

A basic lipid panel reports LDL cholesterol, HDL and triglycerides. Lean, well-trained people often have excellent results on that panel and still carry inherited risk the panel does not show.

Two tests add context. Apolipoprotein B (apoB) counts the number of atherogenic particles rather than the cholesterol they carry. Lipoprotein(a), or Lp(a), is largely set by your genes and barely moves with training or diet. The 2026 ACC/AHA dyslipidemia guideline recommends measuring Lp(a) at least once in every adult's lifetime, and links levels above 125 nmol/L to about 1.4 times the risk of heart attack and stroke.

• Lipid panel plus apoB and Lp(a)
• Blood pressure, ideally measured at home over several days
• Glucose and HbA1c
• A conversation about family history and whether a coronary calcium score makes sense for you

The hormone pattern that endurance can hide

High training volume combined with too little fuel can suppress reproductive hormones in men and women. The International Olympic Committee's 2023 consensus on Relative Energy Deficiency in Sport (REDs) describes this in both sexes and adds newer data on male athletes.

In a man, that can look like low testosterone with low or normal LH, which is easy to mistake for primary low testosterone. The fix may be fueling and recovery rather than a prescription. Before starting testosterone, your clinician will want repeat early-morning tests and a look at your training load and intake. Exogenous testosterone also suppresses your own production and sperm output.

Bones: cycling and swimming are not loading

Running and jumping stress bone in ways that build density. Cycling, swimming and rowing build the heart and lungs but deliver little impact to the hip and spine. Long careers in non-impact sports, especially with periods of under-fueling, can leave bone density lower than you would guess from your fitness.

Adding heavy resistance and some impact work in midlife is one of the more useful changes an endurance athlete can make. Whether you need a bone density scan depends on your age, sex and risk factors, and that scan is done in person.

Rhythm problems deserve attention too

Beyond plaque, long-term endurance athletes, particularly men, are often discussed in relation to heart rhythm problems such as atrial fibrillation. If you notice an irregular pulse, a racing heart at rest, unusual breathlessness or a sudden drop in performance, do not write it off as overtraining or age.

Wearables can flag irregular rhythms, but they are not a diagnosis. An ECG and an in-person evaluation are the right next step, and an online service is not the place to sort out new cardiac symptoms.

What HealifyMD does, and what we refer

A licensed clinician reviews your training history, symptoms and goals, then can order a baseline panel that includes lipids with apoB and Lp(a), metabolic markers, thyroid, iron stores, vitamin D and hormones where relevant. You review the results together in a video or online visit.

We do not do calcium scoring, CT angiography, echocardiograms, stress tests or bone density scans. If your results or symptoms point toward any of those, we will tell you, and you can arrange them with a cardiologist or local provider. Chest pain, fainting or palpitations during exercise need prompt in-person care, not an online visit.