Podcast Summary: What's That Rash?

Episode: Best Time of Day to Exercise?
Date: November 25, 2025
Hosts: Norman Swan & Tegan Taylor
Source: ABC News

Overview

This episode tackles the ever-relevant health question: Is there a “best” time of day to exercise? Inspired by a listener concerned about exercise risks for older adults—particularly the possibility of heart attack or stroke when exercising at certain times—hosts Norman and Tegan dive into what the science says about timing, fitness, age, and personal “chronotype” (whether you're a night owl or early bird). The discussion separates myth from evidence, examines major studies, and leaves listeners with practical advice (plus a few laughs).

Key Discussion Points & Insights

1. Background Risk: Can Exercising at the “Wrong” Time Be Deadly?

• Listener Helen’s Question: Her husband heard that morning exercise, especially without warming up, is dangerous for over-60s. She wants to know if there’s real evidence of increased risk tied to exercise timing and what factors matter most.
• Norman:
  • Regular exercise reduces risk of sudden cardiac death, heart attack, and stroke, regardless of timing.
  • However, there is a natural spike in blood pressure upon waking. If a person with vulnerable artery plaque jumps into strenuous morning exercise, this spike may rarely trigger a heart attack.
  • Epidemiology studies show heart attacks are more common in the morning, but not exclusive to it.
  • Quote:

    "There is an effect on the risk of sudden cardiac death on time of day, of exercise, time of day, and it's thought to be a problem of blood pressure." — Norman [03:36]

2. What Does the Data Say? (UK Biobank Study)

• The UK Biobank tracked about 500,000 people over years—one of the largest health datasets.
• Key Findings:
  • Morning and evening both show small spikes in sudden cardiac death risk.
  • Exercisers overall had LOWER risk than non-exercisers, regardless of time.
  • Chronotype (internal clock) matters:
    • Morning people exercising in the morning had no extra risk; night people exercising at night had no extra risk.
    • "Fighting your nature" raised risk slightly (e.g., night owls exercising early).
• Quote:

  “So if you're a night person and you exercise in the morning, then you had a slightly increased risk of sudden cardiac death... again at a lower level than you would expect because they were exercising.” — Norman [06:16]

3. Making Sense of Risk

• The absolute risk increase is small.
  • Of 94,489 people followed for seven years, only 629 sudden cardiac deaths occurred (about 100/year).
  • For those with “misaligned” exercise timing, risk might go from 1% to 1.5%.
• Quote:

  "Hopefully that puts Helen’s mind at ease... if your risk... was 1%, it maybe went up to 1.5%." — Tegan [07:37]

4. Is There a “Best” Time of Day to Exercise?

• Norman: "Best time to exercise is the one... that you actually can exercise." [08:00]
• While early morning or late evening are labeled “less favorable” in some studies, doing exercise is more important than perfect timing.
• Nearly half of Australian adults do not get enough physical activity—just getting moving matters most.
• Quote:

  "The time of day where you can take exercise and take it easy, build it up." — Norman [13:47]

5. Starting Out: Pace Yourself

• Don’t jump into intense workouts after a sedentary period, especially if over 40 and unfit.
• Build gradually: start with brisk walking and only increase intensity as your fitness improves.
• “No need for embarrassment if out of breath at first—you’ll improve!” [08:35-09:48]

6. Body Clock Effects and Performance

• Exercise acts as a “zeitgeber”—a cue for your body clock.
  • For night owls, some morning exercise may help nudge the body clock earlier.
• Performance specifics:
  • Accuracy-based sports (e.g., tennis) may benefit from morning sharpness.
  • Power and strength (e.g., weight training) may be slightly better in the evening.
  • These are marginal differences, mostly relevant for elite athletes.
• Quote:

  "In sports where you require accuracy... you are probably better in the morning... but there are plenty of sports where you’re a bit better off in the afternoon." — Norman [10:35]

7. Weight Loss & Timing

• Some studies find morning exercise may aid weight control, possibly due to appetite changes (delayed or reduced hunger for breakfast).
• Individual reactions vary.
• Quote:

  "There is quite good evidence that morning exercise helps you control your weight." — Norman [11:44]

8. Who Exercises When?

• Demographics shape exercise time:
  • Midday exercisers are often retired or not employed, with different health and lifestyle patterns.
  • These differences don’t seem to change the heart risk findings.
• “So many different things that might feed into your overall health.” — Tegan [12:35]

9. Bottom Lines and Practical Advice

• Heart Risk:
  • Know your risk factors (cholesterol, blood pressure) and manage them early—even if young.
  • Don’t skip doctor consultations. Podcast isn’t a replacement for medical advice.
• Timing:
  • Do exercise whenever you are most likely to actually do it.
  • Build up gradually, listen to your body, and don’t get hung up on the clock.

Notable Quotes & Memorable Moments

• On ‘Fighting Your Nature’:

  "It was when people were fighting their nature." — Tegan [06:11]
  “Correct.” — Norman [06:14]

• On Absolute Risk:

  "Is that a lot? It sounds like a lot, but it's not really a big proportion." — Tegan [07:12]

• On Practical Priorities:

  “Nearly half, 46% of Australian adults don't meet the physical activity guidelines… one of the biggest ways that we can protect against coronary heart disease.” — Tegan [08:21]

• On Retirement:

  “Don't retire.” — Norman [12:53]
  (Joking about his own age, Norman resists giving up work.)

Timestamps for Key Segments

• 01:51: Listener Helen’s question & concerns
• 02:36: Does exercise timing increase heart attack risk?
• 04:12: Large-scale study findings on timing and chronotype
• 05:40: The importance of chronotype (“night owl” vs “lark”)
• 06:37: How much does risk actually increase?
• 08:00: Is there a “best” time? (Short answer: when you can)
• 09:48: Gradual progression for beginners
• 10:13: Exercise as a body clock cue
• 10:35: Performance differences by time of day
• 11:24: Timing and weight loss
• 12:01: Who exercises when & demographic factors
• 13:15: Summary: what should you actually do?

Final Takeaways (in Their Words)

• Norman:

  "If you're worried, you know, everybody should know their cardiac risk factors... So know what your coronary risk factors are and if they're raised, do something about them, which doesn't necessarily always mean...drugs in conjunction with your doctor and not solely based on the information you hear on a podcast." [13:15]

• Norman (on time of day):

  "Just take exercise. The time of day where you can take exercise and take it easy, build it up." [13:47]

Bottom Line:
Exercise when it works for your body and schedule. Listen to your body’s cues, consider your risk factors, and don’t let the clock be a barrier to simply moving more. The health benefits of exercise vastly outweigh the small, timing-related risks—especially if you match workout time to your natural “chronotype.”

For questions or feedback: Email the hosts at thatrashbc.net.au
Next Week: More unusual health questions—maybe even Norman’s takedown of retirement!