You know the moment. You are six weeks into a training block. The structure is right. The sessions are ticking over. You are sleeping well, eating properly, ticking every box you know how to tick. And something is off. The recovery that used to take 48 hours now takes 72. The motivation that used to be automatic requires effort. The power numbers are there on Monday but not on Thursday.
You blame the training load. You blame the weather. You blame the week at work.
Here is where it gets really interesting. For a significant number of cyclists over 40, the answer is not in the training plan. It is in the blood.
Your hormones are shifting. Not crashing — shifting. And the difference between understanding that shift and ignoring it is the difference between adapting your training intelligently and grinding yourself into the ground wondering what went wrong.
This is not a panic piece. Your hormones are not broken. They are changing at a rate that is entirely predictable, largely manageable, and — in most cases — responsive to things you are already doing or can start doing this week. But you need to know what is happening, what you can influence, and what is simply the price of admission past 40.
Testosterone: The Number Everyone Fixates On and Almost Everyone Misreads
Testosterone declines at roughly 1-2% per year after age 30. That is the number you have probably seen. It is real, it is consistent across large population studies, and it is also deeply misleading without context.
A 1-2% annual decline sounds modest until you compound it. A man who had a total testosterone of 25 nmol/L at 30 could be sitting at 18-20 nmol/L by 45 without any pathology at all. That is a normal, healthy decline. But it is a 20-28% reduction in a hormone that influences muscle protein synthesis, red blood cell production, bone density, mood, motivation, and — critically for cyclists — the speed at which you recover from hard training.
The good news. Total testosterone is only half the story, and it is the less important half.
What matters for performance is free testosterone — the fraction that is not bound to sex hormone-binding globulin (SHBG) and is actually available to muscle tissue. SHBG increases with age, and it increases more sharply in some men than others. Two cyclists with identical total testosterone can have dramatically different free testosterone levels. The one with higher SHBG is getting less of that testosterone into the tissue where it matters.
Andy Galpin has talked about this distinction repeatedly. The total number on your blood panel is a population statistic. The free number is a performance variable. If you are only testing total testosterone, you are reading the headline and skipping the article.
What Testosterone Actually Does for a Cyclist
Let me be really clear about this. Testosterone is not a magic performance hormone. It is a recovery and adaptation hormone. It does not make you faster in the moment. It makes the training you do more productive by supporting:
- Muscle protein synthesis — the rate at which damaged muscle fibres are rebuilt after a hard session
- Red blood cell production — the oxygen-carrying capacity of your blood, which sits underneath everything from FTP to VO2max
- Bone mineral density — increasingly relevant for masters cyclists, who are already at risk from a non-weight-bearing sport
- Neuromuscular signalling — the speed and efficiency of the nervous system's communication with muscle fibres
- Motivation and drive — not in a vague self-help sense, but in the literal neurochemical sense of wanting to train
When testosterone declines, none of these systems fail. They slow down. Recovery takes longer. Adaptation is less efficient. The same training stimulus produces a smaller response. This is why the 45-year-old version of you needs more recovery between hard sessions than the 32-year-old version, even if the fitness is comparable. The training capacity has not disappeared. The hormonal support for absorbing that training has reduced.
The Training Response Is Real
Here is where the conversation gets useful. Training itself is hormonal medicine. High-intensity interval work — the kind of VO2max efforts and threshold intervals that form the hard end of a polarised programme — acutely raises testosterone and growth hormone. The post-exercise spike is temporary, but the cumulative effect of regular high-intensity exposure is a measurable upward pressure on baseline testosterone levels.
Strength training does the same. Two sessions a week of heavy resistance work — and by heavy I mean properly demanding compound movements, not bodyweight circuits — creates an anabolic signalling environment that supports testosterone maintenance. The 2025 meta-analysis covering cyclists over 40 confirmed this: heavy strength training produced performance improvements with no VO2max cost, and the hormonal profile improvements were part of the mechanism.
The reverse is also true. Chronic overtraining without recovery suppresses testosterone. The body interprets sustained stress without adequate rest as a survival threat, and it downregulates reproductive and anabolic hormones accordingly. This is not theoretical. It shows up in blood work. It shows up in performance. And it shows up in the mood and motivation of every masters cyclist who has spent twelve weeks grinding through a training block without a proper recovery week.
Cortisol: The Recovery Thief
Cortisol is not a villain. It is a stress hormone that mobilises energy, reduces inflammation, and prepares the body for effort. You need it. Every training session produces a cortisol spike, and that spike is part of the adaptation signal.
The problem is what happens when cortisol stays elevated.
Chronic cortisol elevation — from training stress, work stress, sleep deprivation, or all three simultaneously — creates an environment that actively opposes recovery. Cortisol is catabolic. It breaks tissue down. Testosterone is anabolic. It builds tissue up. The ratio between them is a better marker of your ability to absorb training than either number in isolation.
The Cortisol-to-Testosterone Ratio
Sports scientists have been using the cortisol-to-testosterone ratio (C:T ratio) as an overtraining marker for decades. When the ratio rises — cortisol up, testosterone down, or both — the body is in a net catabolic state. Training in that state does not produce adaptation. It produces fatigue, stagnation, illness, and injury.
For a masters cyclist, this ratio becomes increasingly relevant because both sides are moving in the wrong direction simultaneously. Testosterone is trending down with age. Cortisol reactivity — the size and duration of the cortisol response to a given stressor — tends to increase. The window between productive training stress and unproductive overreaching gets narrower.
This is why spacing intensity sessions further apart after 40 is not weakness. It is physiology. The 25-year-old who can absorb three hard sessions in five days has a hormonal environment that supports that recovery timeline. The 45-year-old who tries the same thing is running a cortisol-dominant system that has not cleared the previous session before the next one arrives.
What Drives Chronic Cortisol
Training is the obvious one. But for most amateur cyclists with full-time careers, families, and the general chaos of being a functioning adult, the non-training cortisol load is often larger than the training load. Work deadlines, poor sleep, financial stress, relationship tension — all of these produce cortisol that your body does not distinguish from the cortisol produced by five-by-five-minute VO2max intervals.
The total cortisol budget matters. A hard training week on top of a stressful work week is not the same as a hard training week on top of a calm one. Same sessions. Same watts. Completely different hormonal environment. This is one of the reasons that HRV monitoring has become so valuable for masters cyclists — it gives you a proxy readout of your autonomic nervous system state before the session, not after.
Zone 2 training, the low-intensity aerobic work that forms the bulk of a well-structured programme, actively reduces chronic cortisol. The parasympathetic response to easy aerobic exercise is well documented. A proper Zone 2 ride is not just building your aerobic base — it is chemically calming your nervous system and creating the hormonal conditions for recovery from the hard sessions either side of it.
Growth Hormone: The Overnight Repair Crew
Growth hormone (GH) declines at roughly 14% per decade after age 30. By the time you reach 50, your GH output is roughly half what it was at 25. The decline is steeper than testosterone and gets less attention, partly because GH is harder to measure and partly because the supplement industry has less to sell around it.
GH does not directly build muscle in adults the way it does during puberty. What it does is regulate tissue repair, fat metabolism, collagen synthesis, and the downstream production of insulin-like growth factor 1 (IGF-1). For a cyclist, this translates to:
- The speed at which connective tissue — tendons, ligaments, cartilage — recovers from training
- The rate of muscle repair after hard efforts
- The efficiency of fat metabolism during and between sessions
- Bone remodelling, which is already compromised in cyclists due to the non-weight-bearing nature of the sport
Sleep Is the Lever
Here is the good news, and it is substantial. The single most powerful intervention for growth hormone release is deep slow-wave sleep. GH is released in pulses, and the largest pulse of the day — accounting for roughly 70% of total daily GH output — occurs in the first 90 minutes of deep sleep.
This makes sleep quality a direct hormonal intervention. Not a nice-to-have. Not a recovery luxury. A measurable, dose-dependent modifier of the hormone that governs your tissue repair.
Stacy Sims has been writing about this for years, particularly for female athletes approaching and through menopause, where GH decline is compounded by oestrogen loss. Her position is that sleep is the single most underrated performance variable for athletes over 40, and the data backs her up completely.
What disrupts deep sleep in masters athletes is predictable. Alcohol — even moderate amounts — suppresses slow-wave sleep and reduces the GH pulse. Late caffeine does the same, with most people needing a 10-12 hour buffer between their last caffeine and bedtime. Screen exposure in the final hour before sleep delays the melatonin signal that initiates sleep architecture. And training too late — a hard session finishing after 8pm — can elevate core temperature and cortisol enough to delay the onset of deep sleep by 30-60 minutes.
Masters cyclists who fix their sleep hygiene — actually fix it, not just go to bed earlier — often report recovery improvements within two weeks. The blood work catches up later: improved IGF-1 levels, better cortisol clearance overnight, and lower resting inflammation markers. The intervention costs nothing and produces more measurable change than any legal supplement on the market.
Training and GH
High-intensity interval training produces an acute GH spike that can reach 300-500% above baseline. The effect is dose-dependent on intensity and is larger for efforts at or above VO2max than for threshold work. Sprint intervals — short, maximal, with complete recovery — produce the biggest GH response of any training modality.
This is one of the many reasons that a well-structured polarised programme, with genuine high-intensity work at the top end and genuine easy work at the bottom, is hormonally superior to a programme that lives in the middle. The grey zone produces neither the parasympathetic cortisol reduction of Zone 2 nor the anabolic signalling of true high-intensity work. It is the worst of both worlds for your hormonal profile.
Thyroid Function: The Silent Problem in Endurance Athletes
The thyroid is the body's thermostat. It regulates metabolic rate, body temperature, energy production, and the speed of virtually every chemical reaction in the body. When it slows down, everything slows down — including the systems that make you faster on a bike.
Subclinical hypothyroidism — a thyroid that is technically within range but underperforming — affects an estimated 5-10% of the general population. In endurance athletes, and particularly in endurance athletes who have spent years training at high volume on insufficient calories, the prevalence may be higher.
The presentation is frustratingly non-specific. Persistent fatigue that is not explained by training load. Inability to lose weight despite a genuine caloric deficit. Sluggish recovery. Cold intolerance. Dry skin. Low mood. Every one of those symptoms has six other possible explanations, which is why thyroid issues in athletes are chronically underdiagnosed.
What to Test
TSH alone is not sufficient. TSH — thyroid-stimulating hormone — is the screening test your GP runs, and an elevated TSH does flag hypothyroidism. But TSH can be normal while the active thyroid hormones are suboptimal. A proper thyroid panel includes:
- TSH — the pituitary signal. High TSH means the brain is shouting at the thyroid to work harder.
- Free T4 — the storage form of thyroid hormone. Usually normal in subclinical cases.
- Free T3 — the active form. This is the one that actually drives metabolic rate at the cellular level. Low free T3 with normal TSH is the classic subclinical pattern in athletes.
The conversion of T4 to T3 requires adequate caloric intake, selenium, zinc, and iron. Chronic underfuelling — common in cyclists chasing race weight — can impair this conversion and produce a functional hypothyroid state even when the thyroid gland itself is healthy. The gland is fine. The fuel to run it is missing.
If your blood work shows a pattern of low-normal free T3 with adequate TSH, the first question is not whether you need medication. It is whether you are eating enough.
The Blood Work You Should Actually Get
Annual blood work is the minimum. Twice a year is better — once in the off-season as a true baseline, once mid-season to see how training load is affecting things. Taken fasted, first thing in the morning, and ideally during a recovery week. Acute training stress distorts almost every marker worth measuring.
The panel that tells you something useful:
- Complete blood count — haemoglobin, haematocrit, red cell indices. The oxygen-carrying foundation.
- Ferritin — iron stores. The single most common deficiency in endurance athletes, and the one most likely to be quietly destroying your performance. Below 30 ng/mL is functionally low for an athlete, regardless of what the lab range says.
- Total testosterone — the headline number. Useful for tracking trends, less useful as a single snapshot.
- Free testosterone — the number that matters for tissue. Calculated from total T and SHBG, or measured directly.
- SHBG — sex hormone-binding globulin. High SHBG means less free testosterone regardless of total levels.
- Cortisol (morning fasted) — a snapshot of your stress baseline. Trends matter more than absolutes.
- TSH, free T3, free T4 — the thyroid triad.
- Vitamin D — a pro-hormone that affects testosterone production, immune function, bone density, and mood. Below 75 nmol/L is suboptimal for an athlete. Below 50 is deficient.
- Basic metabolic panel — kidney function, liver function, blood glucose. The safety net.
Track trends across years. A single panel is a photograph. A series of panels taken under the same conditions is a film. The film is what tells you whether your testosterone is declining normally or accelerating. Whether your ferritin is stable or drifting. Whether your thyroid function is holding or starting to slip.
Do not get your blood taken the morning after a race, after a heavy training week, or after a night of poor sleep and three glasses of wine. The results will be meaningless. Standardise the conditions. Same time, same state, same phase of training. Then the comparison has value.
What You Can Actually Influence
The interventions with the strongest evidence for maintaining hormonal health after 40 are not supplements. They are behaviours.
Sleep
Seven to nine hours, with attention to quality not just duration. Deep slow-wave sleep is the GH lever. Consistent sleep timing matters more than total hours — going to bed and waking at the same time, including weekends, strengthens circadian rhythm and improves hormonal pulsatility. A dark, cool room. No screens in the final hour. No alcohol within four hours of bed. No caffeine after midday if you are sensitive, early afternoon at the latest.
This is the highest-return intervention on the list. It is free. It requires discipline rather than money. And the evidence behind it is overwhelming.
Training Structure
The programme itself is hormonal medicine. High-intensity intervals acutely raise testosterone and growth hormone. Zone 2 work reduces chronic cortisol. Strength training twice a week maintains anabolic signalling and protects against sarcopenia. The combination of all three — the polarised model with integrated strength — creates the best hormonal environment a masters cyclist can produce through training alone.
What destroys the hormonal environment is monotony and overreaching. Weeks of moderate-hard training without genuine easy days and without genuine rest weeks. The grey zone is not just inefficient for fitness — it is actively harmful for hormonal balance. Not hard enough to trigger the acute anabolic response. Not easy enough to allow cortisol clearance. The worst of both.
Andy Galpin's research supports a masters training week that is more polarised than a younger athlete's — harder on the hard days, easier on the easy days, with more space between intensity sessions to allow the hormonal environment to reset. Not less training. Smarter training.
Body Composition
Body fat is not the enemy, but extremes in either direction are. Very low body fat — below 10% for men, below 18% for women — suppresses testosterone and disrupts thyroid function. The body interprets extreme leanness as a starvation signal and downregulates the hormones it considers non-essential for immediate survival.
This is the race-weight trap. The cyclist who diets down to 6% body fat for a target event may look lean on the start line and feel dreadful on the bike. Testosterone is suppressed. Thyroid conversion is impaired. Cortisol is elevated. The hormonal cost of extreme leanness can exceed the aerobic benefit of reduced weight.
A sustainable range for most male masters cyclists is 12-18% body fat. For most female masters cyclists, 18-25%. These ranges support hormonal health while still being light enough to climb well and perform at a high level.
Nutrition Timing and Adequacy
Chronic underfuelling is the single most common hormonal disruptor in amateur endurance athletes. Not dramatic undereating. The subtle, persistent caloric deficit that comes from training hard and eating "clean" without actually consuming enough. A 300-calorie daily deficit does not feel like anything. Over months, it suppresses testosterone, impairs thyroid conversion, disrupts menstrual function in women, and creates a hormonal environment that resists adaptation.
Protein adequacy matters for hormonal signalling as well as muscle repair. 1.6-2.2g per kg bodyweight per day, spread across four meals, with at least one dose above 35g to clear the leucine threshold that older muscle requires. Stacy Sims recommends 40g+ per meal for post-menopausal female athletes, with a particular emphasis on the post-training and pre-sleep windows.
Vitamin D supplementation if blood levels are below 75 nmol/L. Zinc if dietary intake is inadequate — common in cyclists who avoid red meat. Magnesium, which supports sleep quality and cortisol regulation. These are not testosterone boosters. They are micronutrient sufficiency — filling gaps that impair the system rather than adding to a system that is already working.
What You Cannot Influence
The rate of decline itself. Testosterone will decline at 1-2% per year. Growth hormone will decline at roughly 14% per decade. SHBG will increase. These are biological facts that no training programme, supplement stack, or lifestyle intervention will reverse in a healthy individual.
What you can influence is where within the normal range you sit. A 50-year-old man with good sleep, appropriate training, adequate nutrition, healthy body composition, and managed stress will typically sit at the higher end of the age-adjusted reference range. The same man with poor sleep, chronic overtraining, caloric restriction, and high life stress will sit at the lower end. The range between those two positions can be the difference between feeling 40 and feeling 60.
You are not fighting age. You are managing the variables that determine how age expresses itself. The hormonal trajectory is fixed. The position on that trajectory is modifiable.
The Line Between Evidence and Bro-Science
The supplement industry has built a billion-dollar market on the fear of hormonal decline. Testosterone boosters, GH secretagogues, cortisol blockers, thyroid support complexes — the shelves are full, the claims are large, and the evidence is almost universally thin.
The interventions with real evidence behind them are boring. Sleep. Food. Training. Vitamin D if deficient. Zinc if deficient. Magnesium for sleep quality. Creatine monohydrate, which has strong evidence for muscle function and recovery, though its effect on hormones specifically is indirect.
Ashwagandha has modest evidence for cortisol reduction — a few well-designed trials showing a measurable decrease in cortisol and a small increase in testosterone in stressed populations. It is not a testosterone booster. It is a stress modulator. The distinction matters because the effect disappears if your stress is already well managed.
Everything else — tribulus, fenugreek, D-aspartic acid, DHEA, boron, the proprietary blend in the black bottle with the aggressive label — has either no evidence, conflicting evidence, or evidence so weak that the effect size is smaller than the measurement error. You are better off spending that money on a blackout blind and a week's supply of high-quality protein.
TRT: A Medical Decision, Not a Training Decision
Testosterone replacement therapy is a legitimate medical intervention for men with clinically low testosterone confirmed by repeated blood work and accompanied by symptoms. It is not a performance shortcut. It is not something to adopt because a podcast guest or a men's health influencer made it sound simple.
Clinical guidelines generally consider total testosterone below 8-12 nmol/L (230-350 ng/dL), confirmed on at least two separate morning fasted draws, combined with symptoms — persistent fatigue, loss of motivation, reduced recovery capacity, low libido, depressed mood — as the threshold for considering intervention.
For competitive cyclists, TRT carries regulatory implications. It is a banned substance under WADA rules and most national anti-doping frameworks. Even in amateur racing categories that do not test, many organisations have explicit policies. A Therapeutic Use Exemption (TUE) may be available in some sanctioned events, but the process is rigorous and the bar is high.
For non-competitive cyclists, the decision is between you and your doctor. Not your training partner. Not a forum. Not an Instagram account with a discount code. A clinician who has seen your blood work, assessed your symptoms, and can monitor your levels over time.
What I would say is this. Before you consider exogenous testosterone, exhaust the endogenous interventions first. Fix your sleep. Fix your nutrition. Fix your training structure. Fix your stress management. Get the blood work done under standardised conditions, twice, months apart. If everything is dialled in and you are still symptomatic with confirmed low levels, that is a conversation worth having with someone who went to medical school. If you have not fixed the basics, you are medicating a lifestyle problem and you will still have the lifestyle problem when the prescription runs out.
The Female Athlete Perspective
Everything above applies to men and women, but the female hormonal picture has additional layers that deserve specific attention.
Perimenopause — the transition period that can begin as early as the late 30s and last a decade — involves dramatic fluctuations in oestrogen and progesterone that affect thermoregulation, sleep quality, body composition, mood, joint laxity, and recovery capacity. The swings are often more disruptive than the eventual decline, because the body is constantly recalibrating.
Post-menopause brings a steep and permanent decline in oestrogen and progesterone. Stacy Sims' research has reshaped how female athletes approach this transition. Her key recommendations: increase protein to 40g+ per meal to overcome anabolic resistance, prioritise high-intensity interval work over volume to maintain muscle mass and metabolic rate, include bone-loading exercise (jumping, impact work) to counter the accelerated bone density loss that follows oestrogen decline, and pay specific attention to cooling strategies because thermoregulation changes are real and measurable.
The performance impact of menopause is real. It is also highly modifiable. The women in our community who have approached this transition with good information and specific adjustments — rather than the vague advice to "listen to your body" that passes for guidance in most cycling spaces — have not just maintained performance. Several have set personal bests.
Putting It Together
Your hormones are changing. That is a fact. It is not a crisis. It is a variable, and like every other variable in your training, it responds to the right inputs.
The right inputs are not exotic. They are the fundamentals done with precision and consistency. Sleep that prioritises quality and duration. Training that is properly polarised, with real intensity and real rest. Nutrition that provides enough fuel, enough protein, and enough micronutrients to support the hormonal machinery. Strength work that maintains anabolic signalling. Stress management that keeps cortisol within a range your recovery systems can handle.
Blood work gives you the data to know whether those inputs are working. Annual at minimum. Standardised conditions. Tracked over time. Not as a source of anxiety, but as a feedback loop — the same way you use a power metre to track your training, use blood work to track the system underneath the training.
The science has finally caught up on most of this. The evidence base for sleep, training structure, nutrition adequacy, and hormonal monitoring in masters athletes is stronger than it has ever been. The gap is not in the knowledge. It is in the application — in the willingness to treat these variables with the same seriousness you give to your interval sessions and your race calendar.
You are not done. Your hormones are not telling you to stop. They are telling you to be smarter. And if you have read this far, you already are.
If you want to talk about any of this with riders who are working through the same questions, the Roadman Cycling community on Skool is where that conversation happens. Blood work, recovery protocols, training structure for masters cyclists — it is all on the table, every week, with people who take this as seriously as you do.