Over 38, How Long does it take you to Lose your Fitness?

How Long Does It Take to Lose Fitness Levels?

Exercise plays a critical role in promoting general well-being and extending healthspan, but a question often arises: how long does it take for fitness levels to decline after stopping regular physical activity? Understanding this timeline is essential for those who have dedicated time and effort to build their fitness. In other words, how long can one take a break before fitness levels start to deteriorate?

This review explores a piece written by Dan Gordon, Associate Professor of Cardio-respiratory Exercise Physiology, and Justin Roberts, Associate Professor of Health and Exercise Nutrition, both from Anglia Ruskin University, addressing this very issue.

Use It or Lose It: The Reality of Fitness Decline

Achieving peak fitness is a challenging process, but maintaining it is equally demanding. According to research, fitness levels decline at a faster rate than it takes to improve them. While substantial effort is required to build fitness, taking time off from training can result in becoming "unfit" more quickly than anticipated.

How Fitness Declines

To understand how fitness levels deteriorate, it’s important to first comprehend how fitness is developed. The key to improving fitness, whether in cardiovascular endurance or muscular strength, is to consistently exceed the body’s habitual load. This means pushing the body beyond its normal routine, which forces it to adapt and grow stronger over time.

How Long Does It Take to Get Fit?

The time required to achieve fitness depends on several factors, including baseline fitness, age, intensity of training, and environmental conditions. Studies suggest that as few as six sessions of interval training can improve maximal oxygen uptake (V02 max), a crucial measure of fitness, and enhance the body’s ability to efficiently use stored fuel during exercise.

In strength training, initial gains in muscle strength can be observed within two weeks, though visible changes in muscle size typically take 8-12 weeks to manifest.

Cardiovascular Fitness Decline: A Case Study

Once training ceases, the rate at which fitness declines depends on various factors, including the specific type of fitness (e.g., cardiovascular endurance versus strength). For example, consider a marathon runner who has spent years developing peak athletic performance, running five to six days a week and covering 90 kilometers weekly.

If this runner stops training altogether, the body, no longer under the stress of exercise, will begin losing fitness in a matter of weeks. Research shows that V02 max, the amount of oxygen a person can use during exercise, decreases by approximately 10% in the first four weeks of inactivity. This rate of decline continues at a slower pace over time.

V02 Max Decline in Athletes vs. Average Individuals

Interestingly, while highly trained athletes like marathon runners experience a rapid drop in V02 max within the first four weeks of detraining, their decline eventually levels off, allowing them to maintain a higher V02 max than the average person. For the average individual, however, V02 max may plummet to pre-training levels within just eight weeks. This decline is largely attributed to reductions in blood and plasma volumes, which can decrease by as much as 12% in the first four weeks of inactivity.

The Role of Blood and Plasma Volume

Plasma and blood volumes decrease when the heart and muscles are no longer stressed by regular training. In fact, plasma volume can decrease by around 5% within the first 48 hours of stopping exercise. This reduction leads to less blood being pumped throughout the body with each heartbeat. Though these levels only drop back to where they started before training began, even recreational exercisers are not immune to this rapid decline in cardiovascular adaptations.

Strength Training Decline

When it comes to strength, research shows that after 12 weeks without training, individuals experience a significant decrease in the amount of weight they can lift. However, even after extended breaks from strength training, some of the strength gains achieved prior to detraining are retained. This is because, although muscle strength declines, the size of the muscle fibers only decreases minimally.

The primary reason for the decline in muscle strength is the reduction in stress placed on the muscles during inactivity. Without regular use, muscles become “lazy,” leading to a decrease in the number of fibers recruited during physical activities. After just two weeks without training, the number of muscle fibers recruited for exercise drops by approximately 13%, though this initial decline does not significantly affect muscle force.

Muscle Fiber Loss and Long-Term Decline

Over longer periods of detraining, the decline in muscle mass combined with the initial reduction in muscle fiber recruitment results in significant strength losses. Gym-goers who stop lifting weights will notice a decrease in muscle size over time, making it harder to lift heavy loads due to fewer muscle fibers being activated.

Cardio and Strength Loss Timeline

Fitness declines begin within 48 hours of stopping exercise. Cardiovascular fitness may begin to deteriorate after two to three weeks, while strength levels typically start to decline after six to 10 weeks of inactivity. Notably, the rate of detraining is similar across genders and age groups, though those who maintain a higher level of fitness tend to lose their gains more slowly over time.

The Impact of Detraining on Longevity

For those exercising with longevity in mind, detraining has important implications. As individuals age, natural declines in energy levels and motivation to exercise can lead to less frequent physical activity. Dietary habits also tend to shift, with older adults often consuming less protein, which impacts the body’s ability to maintain muscle mass. This contributes to age-related muscle loss, known as sarcopenia.

Injury risk also increases with age, and recovery time becomes longer. These factors combined make it essential to adopt a consistent exercise routine that prioritizes both cardiovascular health and strength training.

Building a Longevity Plan

To combat age-related fitness decline, older adults should focus on consuming sufficient high-quality protein and incorporating resistance training into their routines. Regular aerobic exercise that raises the heart rate and induces breathlessness for at least 10 minutes daily is also recommended. If a break from training is necessary, it should not extend beyond 14 days. However, consistency remains key, and individuals should aim to engage in some form of exercise—whether cardiovascular or resistance training—every day.

Maintaining a balanced approach to fitness is crucial for long-term health and longevity. Even brief periods of inactivity can result in noticeable declines in fitness, underscoring the importance of a sustained, well-rounded exercise regimen.