Everyone has taken breaks from a fitness routine. Vacation, the flu, work responsibilities, life happens. Let's Start with this question: How long does it take to get fit... in the first place?
The fun answer: It depends! For example, world class marathon trainers take fifteen years to achieve their level of fitness. For those of us who can’t run 26.2 miles in two hours and thirty minutes, the phrase “getting in shape” varies by several factors. Whether you’re training for a marathon or want to hit the elliptical for thirty minutes, it takes work to achieve the level you're eye is set on. But then, you have to maintain it (that's called consistency).
If we stop training, we can lose fitness much faster than it took to build. Increased fitness, whether from cardiovascular endurance or strength training, is caused by exceeding our habitual load- pushing our bodies to adapt. However, once this stress is removed, the body reverts to a less fit state.
Fitness improvements depend on various factors, including baseline fitness, age, training intensity, and environment. Research bases fitness criteria in two forms: cardiovascular (aerobic) fitness, and strength training.
Cardiovascular fitness can improve in just six sessions of interval training, boosting VO₂ max (a key measure of aerobic fitness).
Strength training shows muscle force gains in two weeks, but visible increases in muscle size take 8-12 weeks.
Cardiovascular Fitness Decline
When training stops, cardiovascular fitness begins to decline rapidly. VO₂ max drops by 10% within four weeks, continuing to decrease more slowly over time.
Highly trained athletes experience an initial sharp drop but maintain a higher-than-average VO₂ max even after prolonged inactivity.
Non-athletes see VO₂ max fall back to pre-training levels in less than eight weeks.
The decline in VO₂ max is primarily due to reductions in blood and plasma volume, which decrease by as much as 12% in four weeks. Plasma volume alone can drop 5% within 48 hours of stopping training. This leads to less blood being pumped per heartbeat, making exercise feel harder when resumed. However, plasma and blood volume only return to baseline, meaning cardiovascular fitness won’t drop below pre-training levels.
Strength Loss After Stopping Training
In contrast to cardiovascular fitness, muscle strength declines more slowly. After 12 weeks of inactivity, the weight a person can lift significantly decreases, but muscle size remains relatively stable.
Within two weeks, the number of muscle fibers recruited during exercise drops by 13%, though muscular force remains unchanged.
Over longer periods, muscle fibers continue decreasing, along with a gradual loss of muscle mass, making it harder to lift heavy loads.
The fitter a person is, the slower they lose strength.
Muscle loss occurs because without regular stress and resistance, muscles become less efficient, leading to fewer fibers being activated during activity. Casual weightlifters may notice their muscles shrink and find it harder to lift as they lose muscle fiber recruitment over time.
How Fast Do We Become Unfit?
Cardiovascular fitness starts declining within 48 hours, but noticeable effects appear after 2-3 weeks.
Strength declines begin around 6-10 weeks.
Men and women experience similar rates of detraining, and older individuals face similar declines.
The key takeaway? The fitter you are, the slower you lose fitness. While detraining happens quickly, regular maintenance workouts can help retain fitness levels for longer.