Why Detraining Is At The Heart Of The Swimming Playbook In Covid-19 Season 2020

Swimming Muscle - Photo Courtesy: compilation, top to bottom: - Patrick B. Kraemer (Adam Peaty); Backcountry Digital (torso); FINIS (Anthony Ervin)

Detraining is a natural physiological phenomenon that plays out in the body when an athlete ceases regular training. Any swimmer who has ever followed an intense season with a 2-3-week break and then returned to face the music will know what ‘what’s gained in three weeks is lost in a day’ feels like.

Forced lockdown during COVID-19 has brought detraining into sharp focus as swimmers, coaches and programs make their way back to water and pool deck.

To use the words of Pieter van den Hoogenband‘s dad Dr Cees-Rein van den Hoogenband:

“… detraining … results in a diminished efficiency of heart and lungs to transport oxygen and use this in active muscles (i.e. reduced cardio-respiratory efficiency, and a diminished capacity of skeletal muscle to display strength, flexibility and endurance (i.e. reduced musculoskeletal capability). Given the changes in energy expenditure, individual nutritional requirements will also change.”

Dr. Van den Hoogenband, in his role as the chairman of the FINA Sports Medicine Committee advising the FINA COVID-19 Task Force backed by guidance from the World Health Organisation (WHO) and Government Agencies, issued a statement this week to coincide with the permissions being granted or considered by Public Health Authorities in many countries for a limited return to swimming pools and “on the understanding that hygiene measures, hand washing, physical distancing and contact tracing initiatives are observed”.

As we noted in a two-art feature with water health and hygiene expert Dr. Vincenze Spica (part 1 ; Part 2), there are reasons to be optimistic, reasons why elite swimming in control conditions can be revived. There are also, say scores of experts, cautionary measures that need to be observed at a time when more needs to be known about the nature of the novel coronavirus behind the current pandemic in which 7.6m people have been infected and more than 424,000 have died as a result of COVID-19, according to official registered statistics.

In his nite to swimmers, coaches and programs, Dr. Van den Hoogenband raises an issue critical to the health, welfare and successful return of athletes. He writes:

“The SMC respectfully reminds all stakeholders that athletes, forced into an unprecedented and prolonged break from habituated training routines, may experience the physical effects of ‘detraining’. …

“For professional athletes with access to expertise in sports science and medicine, we understand that these issues will have already been anticipated and, to some extent, minimised by land-based exercise. However, many FINA athletes do not enjoy these privileges and it is inevitable that all athletes will be affected to some extent. Sport specific fitness for aquatic athletes can only be fully achieved through water-based activities.

“The SMC wishes to raise these issues for the benefit of all aquatic athletes. We advise a gradual resumption of training, balancing water-based and land-based activities and increasing these elements slowly, starting with low and medium intensity exercise. This will allow your body to readjust and minimise the risk of overuse injury through failure to adapt to increasing workload. Rising energy demands of training will also require appropriate nutritional intake.

“We also appreciate the psychological impact the COVID-19 pandemic has had on athletes, affecting normal interactions and routines, and as a consequence of postponement or cancellation of FINA events. Return to competition fitness will take several months and FINA will take this into account when making future decisions.”


As Dr Van den Hoogenband noted, many of the world’s best swimmers and their coaches have access to experts and good resources when it comes to detraining. Iñigo Mujika, the physiologist who works with coach Fred Vergnoux and team at Spanish swimming, is among those who has long considered the theme in academic work that feeds into the coaching of world-class swimmers, among other athletes.

Detraining is nothing new. Back in the days of the GDR, swimmers were ‘detrained’ for up to two years after their last races, Kornelia Ender revealing back in 1993 in an interview with this author that she “swam down” and eased out of the sport over a period of almost two years. Part of the reason for that, according to medical papers recovered from Stasi (state police) files after the fall of the Berlin Wall in 1989, was to attempt to reverse the androgenization of girls fed steroids since they were 13 years old. The issues raised are relevant to the current debate on gender in sport. Like so many things in this world, there is a light and dark side to the coin of knowledge.

Understanding detraining and taking the theme into account as swimming programs embrace a steady revival speaks to the best interests of athletes (including those who were abused with doping from a young age). Science developed in the GDR in what was the biggest experiment ever undertaken on athletes (an estimated 10,000 were affected), made its way to the library of understanding in world swimming long ago. Science does not stand still, of course, and much more has been learned since Ender and Co were swum down.

In 2001, Mujika co-authored a paper with Sabino Padilla in which they considered the “Cardiorespiratory and metabolic characteristics of detraining in humans” (available free at that link). They wrote:

“Detraining can be defined as the partial or complete loss of training-induced adaptations, in response to an insufficient training stimulus. Detraining is characterized, among other changes, by marked alterations in the cardiorespiratory system and the metabolic patterns during exercise. In highly trained athletes, insufficient training induces a rapid decline in O2max, but it remains above control values. Exercise heart rate increases insufficiently to counterbalance the decreased stroke volume resulting from a rapid blood volume loss, and maximal cardiac output is thus reduced. Cardiac dimensions are also reduced, as well as ventilatory efficiency. Consequently, endurance performance is also markedly impaired.

“These changes are more moderate in recently trained subjects in the short-term, but recently acquired O2max gains are completely lost after training stoppage periods longer than 4 wk. From a metabolic viewpoint, even short-term inactivity implies an increased reliance on carbohydrate metabolism during exercise, as shown by a higher exercise respiratory exchange ratio. This may result from a reduced insulin sensitivity and GLUT-4 transporter protein content, coupled with a lowered muscle lipoprotein lipase activity. These metabolic changes may take place within 10 d of training cessation. Resting muscle glycogen concentration returns to baseline within a few weeks without training, and trained athletes’ lactate threshold is also lowered, but still remains above untrained values.”

Their conclusion reads: “Detraining, defined as the partial or complete loss of training-induced adaptations in response to an insufficient training stimulus, may take place within short periods of training cessation or marked reduction in habitual physical activity level. Short-term cardiorespiratory detraining is characterized in highly trained athletes by a rapid O2max decline, but it usually remains above sedentary values. O2max decreases to a lesser extent in recently trained subjects in the short run, but training-induced gains are most often completely reversed when training is stopped for a period longer than 4 wk. The O2max loss is the outcome of an immediate reduction in total blood and plasma volumes, the latter being caused by a reduced plasma protein content.

“Even though exercise heart rate increases at both maximal and submaximal intensities, this is not sufficient to counterbalance the reduced stroke volume, and maximal cardiac output declines. Cardiac dimensions often decrease, blood pressure increases, and ventilatory efficiency is most usually impaired after periods of training cessation. This general loss in cardiorespiratory fitness results in a rapid decline in the trained athletes’ endurance performance. Recently acquired endurance performance gains, on the other hand, can be readily maintained for at least 2 wk without training.

“From a metabolic perspective, even short-term detraining is characterized by a higher reliance on carbohydrate as a fuel for exercising muscles, as indicated by an increased respiratory exchange ratio. Whole-body glucose uptake is reduced, because of a decline in insulin sensitivity and a reduced muscle GLUT-4 transporter protein content, both in athletes and in recently trained individuals. In addition, muscle lipoprotein lipase activity decreases. Exercise blood lactate concentration increases at submaximal intensities, and the lactate threshold is apparent at a lower percentage of O2max. These changes, coupled with a base deficit, result in a higher postexercise acidosis. Finally, muscle glycogen concentration suffers a rapid decline, reverting to sedentary values within a few wk of training cessation.”

Detraining In Covid-19 Season


Dr. G. John Mullen recently published the highlights of a conversation he had with Dr. Rodrigo Zacca, Ph.D, a Postdoctoral Researcher of Universidade do Porto in Portugal. Dr. Zacca studied the “Effects of detraining in age-group swimmers performance, energetics and kinematics“.

On his Swimming Science blog, Dr. Mullen penned the “9 Things you Didn’t Know about Swimming Detraining” as a result of his conversation with Dr. Zacca. Here are the seven themes covered (read the article in full at Swimming Science for the detail):

Swimming Impairs: …  the main conclusions of this study suggest that detraining after four-weeks of pool-based training cessation can impair swimming performance at the start of the following training season in age-group swimmers, underlining the importance of maintaining fitness levels during off-season or swimming detraining.

3.8% Impairment: The 400-m front crawl performance of 14–15 years old competitive swimmers was impaired by ~3.8% after four-weeks of training cessation …

No Effects from Growth: Four-weeks was not long enough to detect growth effect on performance, but impairment of 400m front crawl performance was attenuated by those swimmers who were more physically active during the off-season.

Elite Swimmers 4-Week Detraining: For elite swimmers, there are three interesting studies.

  • Costill et al. (1985) brought us valuable information back in the mid-1980s. After 20 weeks of intense training, male swimmers were evaluated during 4 weeks of training cessation. Skeletal muscle oxidative capacity (biopsy from deltoid muscle) decreased by 50% after one week, but remained similar during the subsequent weeks. Muscle phosphofructokinase and phosphorylase activities remained similar. Muscle glycogen gradually reduced. Baseline [La−] peak values after swimming 200 yards (~183 m) at 90% of swimmer’s best time was 4.2 ± 0.8 mmol ∙ l -1 , increasing to ~ 9.7 ± 0.8 mmol ∙ l -1 after 4 weeks. Impairments in performance higher [La−] peak values were the combined result of a decline in muscle´s respiratory capacity and diminished oxygen transport system.
  • 3x/week Detraining in Elite Swimmers: Another cool study was performed by Neufer et al. (1987). Following five months of competitive training, three groups of male swimmers performed 4 weeks of either training reduction or cessation. Reduction in swimming training to only 1 ∙ week -1, with ~30% of prior training volume/load (9000 yards ∙ day-1; “intense training”), did not provide enough stimulus to preserve the aerobic power (V̇O2max) in male swimmers. However, reduction in swimming training to only 3 ∙ week -1, with ~30% of prior training loads, results in little or no decrement in V̇O2max. Besides, muscular strength is not impaired over 4-weeks of training reduction or cessation. However, power (biokinetic swim bench system) is impaired in both cases (training reduction or cessation). Despite that, impairments in performance are markedly less when swimmers continue to train even only 3 ∙ week -1 with ~30% of prior training volume/load.
  • 2 Month Detraining in Elite Swimmers: Finally, the impact of 2-months training cessation (swimming detraining) on diet and body composition was studied by Almeras et al. (1997) in elite female swimmers. The authors observed that body weight gain (4.8-kg) and body fat gain (~ 4 kg of fat mass) occurs in response to training cessation.

High-Intensity Maintains Performance: Non-swimming specific physical activities during the offseason or swimming detraining accounted for 40% of the total variance in performance, showing good partial correlation with impairment in performance …

How Long to Get In Swimming Shape After Covid-19: Many factors will influence the length of time for recovery from Covid-19. Size and speed to reverse these losses after the #Covid19 will depend on many aspects, such as current fitness level, training history, age, specificity of previous training, and even genetics (Mujika and Padilla 2000-01; Abrahin et al. 2019). However, since the pandemic is not over yet and we do not know when it will end, it’s time to attenuate the impairments in performance. Those who manage to remain more active (in a creative and intelligent way) will have fewer problems after this pandemic period.

Other Tips on Limiting Impairments from Swimming Detraining: First, don’t stand waiting for the end of pandemic, as the impairments can be irreversible … Second, be creative to create alternatives, but be intelligent (specificity matters a lot).

Dr Mullen notes that study of detraining and related issues was not the exclusive preserve of sport and the theme dovetails with other important factors in performance swimming, such as injury, health, disease; Taper; Off-season; “… and now a pandemic”.

“Understanding the effects of training reduction and cessation is of interest to other communities and society in general,” writes Dr Mullen, noting the importance of the issue to the military, aerospace industry, care for and wellbeing of the elderly and the bedridden and those who suffer from conditions involving the loss of autonomy, including ageing, muscle disorders and related disabilities).


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