Hard and Intense Exercise May Hold the Key To Ageing Better, New Study Finds

A new study published in Medicine & Science in Sports & Exercise has examined how hard people in their 70s should exercise to help preserve aerobic fitness as they age. The research team, led by Sindre Midttun of the Norwegian University of Science and Technology, analysed data from the 'Generation 100' study in Trondheim, Norway, focusing on how exercise intensity affected participants' fitness levels over a five-year period.

Generation 100 included about 1,500 people aged between 70 and 77. Participants were originally assigned to either follow public health guidelines, complete twice-weekly moderate exercise at 70 per cent of maximum heart rate, or perform intense exercise at 80 per cent. The programme lasted five years.

The original results, published in 2020, found little difference in mortality between the groups. However, participants could exercise outside the supervised sessions, and the control group often exercised more intensely than the moderate-exercise group.

High-Intensity Exercise Linked to Smaller Fitness Decline

For the new analysis, researchers focused on what participants actually reported doing rather than their original assigned groups. They selected 500 people who consistently reported either moderate or high-intensity exercise during the five-year period.

Moderate exercise was defined as 11 to 14 on the Borg scale, ranging from fairly light to somewhat hard. High-intensity exercise was rated at 15 or above, covering hard, very hard and 'very, very hard' efforts.

The two groups exercised for similar amounts of time and at similar frequencies. Researchers then compared changes in their VO2 max, a measure of aerobic fitness.

Both groups lost fitness over the five years, reflecting the challenges of maintaining aerobic capacity in older age. However, those who exercised at higher intensity experienced a smaller decline.

Among men, the high-intensity group recorded a 3.1 per cent decline in VO2 max from baseline after five years, compared with a 7.7 per cent decline among those exercising at moderate intensity.

Women fared slightly better. After five years, the high-intensity group had returned to its baseline fitness level, while the moderate-intensity group recorded a 4.6 per cent decline.

Findings Offer Perspective on Zone 2 Training

The findings come amid growing interest in zone 2 training, which involves exercising at a moderate intensity below a person's threshold. Supporters argue that this approach promotes fat burning and mitochondrial adaptations while allowing people to accumulate larger amounts of training.

Polarised training similarly emphasises mostly easier exercise, combined with a smaller amount of harder work. However, the study does not directly disprove the benefits of zone 2 training.

The proponents did not establish precisely which training zones participants were exercising in, and perceived effort cannot be directly equated with heart-rate or metabolic zones.

Instead, the results reinforce the broader idea that, within reasonable limits, higher-intensity exercise can produce greater fitness benefits. For older adults, the study suggests that exercising harder may help limit the decline in aerobic fitness that naturally occurs with age.

The findings also provide important context for easier training. Zone 2 may remain useful because holding back during some sessions can allow people to train more overall, recover more effectively, or push harder during other workouts.

Rather than being a shortcut to fitness, easier sessions can help create a balanced training routine that allows for greater effort when it matters most.