REVIEW
Detraining
attenuation during the COVID-19 pandemic: practical considerations for
home-based strength and power training
Atenuação do destreinamento durante a pandemia de COVID-19:
considerações práticas para o treinamento de força e potência em ambiente
doméstico
Lucas
Guimarães-Ferreira1,3, Danilo Salles Bocalini2,3
1Muscle Physiology and
Human Performance Research Group, Center of Physical Education, Federal
University of Espirito Santo, Vitória/ES, Brazil.
2Translational
Physiology Applied to Health, Sport and Human Performance Research Group,
Center of Physical Education, Federal University of Espirito
Santo, Vitória/ES, Brazil.
3Postgraduate Program in
Physical Education, Center of Physical Education, Federal University of Espirito Santo, Vitória/ES, Brazil.
Received
on: 2020, May 6; accepted 2020, May 9.
Corresponding author: Lucas
Guimarães-Ferreira, Federal University of Espirito Santo, Center of Physical Education,
Fernando Ferrari Ave, 514, 29075-910 Vitória/ES, Brazil.
Lucas Guimarães-Ferreira:
lucas.ferreira@ufes.br
Danilo
Salles Bocalini: bocaliniht@hotmail.com
Abstract
The
COVID-19 pandemic that scattered across the world in 2020 has required
collective action to control the transmission of the disease. Among the
measures, social distancing has been widely adopted, aiming to reduce contact
and people gathering. With the limited access to training places that have
equipment and a variety of loads for strength and power training, alternative
strategies to be carried out in the domestic environment are important for
maintaining physical conditioning and mitigating the deleterious effects of
detraining. Based on the available scientific literature, this article presents
practical recommendations for strength training in the home environment. It is
recommended to perform exercises that employ self-body weight, household items
and, when available, dumbbells and elastic bands. Whenever using low loads
(30-50% of 1 repetition maximum), performing the sets until the concentric
failure seems to be necessary to optimize gains in strength and muscle mass.
The practice of physical exercises should be performed on most days of the week
(> 5 days/week), combined with domestic and leisure activities that involve
the movement of the whole body. For maintenance and / or development of muscle
power, ballistic movements must be included, in the presence or absence of
external loads.
Keywords: strength training, power, detraining, COVID-19.
Resumo
A pandemia de COVID-19
que se espalhou por todo o mundo em 2020 demandou ações coletivas para controle
da transmissão da doença. Dentre as medidas adotadas, o distanciamento social
vem sendo amplamente adotado, visando a redução do contato e aglomeração de
pessoas. Com a limitação ao acesso a locais de treinamento que dispõe de
equipamentos e variedade de carga para o treinamento de força e potência, estratégias
alternativas para realização no ambiente doméstico se fazem importante para
manutenção do condicionamento físico e atenuação dos efeitos deletérios do destreinamento.
Utilizando como base a literatura
científica disponível, o presente artigo apresenta
recomendações práticas para
o treinamento de força no ambiente doméstico.
Recomenda-se a utilização de
exercícios que utilizam o peso do próprio corpo, itens
domésticos e, quando
disponíveis, halteres e bandas elásticas. Ao se utilizar
baixas cargas (30-50%
de 1 repetição máxima), a realização
das séries até a falha concêntrica parece
ser necessária para otimizar os ganhos de força e massa
muscular. A prática de
exercícios físicos deve ser realizada na maioria dos dias
da semana (>5
dias/semana), combinada a atividades domésticas e de lazer que
envolvam a
movimentação de todo o corpo. Para
manutenção e/ou desenvolvimento da potência
muscular, movimentos balísticos devem ser incluídos, com
ou sem cargas
externas.
Palavras-chave: treinamento de força,
potência, destreinamento, COVID-19.
COVID-19 is an infectious respiratory disease caused by the SARS-CoV-2
coronavirus that became a pandemic in a short period of time during the year
2020 [1]. Until April 13, 2020, 1.9 million cases were registered, with 118
thousand deaths worldwide [2]. Among the various preventive measures adopted by
the World Health Organization and local governments, social distancing has been
shown to be effective in preventing the spread of the disease [3]. During this
delicate period, many cities in the world banned access to closed places,
including training spaces, such as sports clubs and gyms, given that the
crowding of people represents a threat.
The maintenance of physical fitness during the period of social
distancing, both from the perspective of health and sports performance, is of
great importance. Thus, this article aimed to discuss, through a narrative
review of the scientific literature, alternatives for maintaining neuromuscular
function without needing large and/or high cost equipment to be performed in
the home environment. Finally, we summarize possible strategies and practical
recommendations for home-based exercise during social isolation and distancing
currently adopted.
Detraining
When physical training is interrupted, the adaptations obtained
previously are reversed, until reaching the pre-training values. This
phenomenon is known as detraining [4,5]. However, once a certain training
adaptation has been achieved, considerably less training stimulus is required
to maintain it, when compared to that necessary to develop it in the first
place [6]. This means that even when there is a reduction in the training
stimulus, but not its complete interruption, it seems possible to attenuate or
even prevent reductions in physical conditioning.
A study with elderly participants showed that a strength training
program for 12 weeks results in an increase in muscle strength and power by 10
to 36% [7]. In contrast, detraining for the same 12-week period led to a 5 to
15% reduction in the same parameters. These results suggest that when analyzing
the temporal pattern of training and detraining, it is possible that the latter
occurs at a slower pace, allowing a partial maintenance of the gains obtained
from previous strength training after a detraining period of the same duration.
Such findings were corroborated in young adults by Psilander
et al. [8]. Men and women underwent 10 weeks of a strength training
program, which resulted in an increase in the cross-sectional area of muscle
fibers (+ 17%), muscle thickness (10%) and strength (+ 20%). After 20 weeks of
detraining, the diameter of the muscle fibers and the muscle volume returned to
pre-training values, but muscle strength was partially remained (at ~60%). The
motor learning effect involved in strength training seems to be maintained for
a longer time during detraining when compared to the morphological changes of
the muscle fibers.
A short period of detraining may be enough to develop detrimental
changes in neuromuscular function in athletes. 2 weeks of complete interruption
of training in 12 athletes resulted in a 19.2% reduction in type II muscle
fibers area, although type I fiber area remained unchanged. The performance in
bench press, squat and vertical jump decreased by -1.7, -0.9 and -1.2%,
respectively. Although changes in strength and power have not shown statistical
significance, they deserve attention in view of the short detraining time and
the importance that small changes can present for high-performance athletes.
When compared to strength, muscle power seems to be affected earlier during
detraining. In moderately strength-trained men, 6 weeks of detraining caused a
significant reduction in power, without significant changes in maximum strength
measured with the 1-maximum repetition test (1RM) [9].
Considering the temporary nature of social distancing, with a probable
duration of a few weeks, it is expected that after this period practitioners,
athletes or not, will return to the strength training facilities. Individuals
with experience in strength training, after a detraining period, seem to
present gains in muscle strength and hypertrophy at a higher pace when compared
to untrained individuals [10]. This phenomenon is commonly known as “muscle
memory”, which in the past was attributed to motor learning and intermuscular
coordination, (neural factors) [11]. More recently, however, some authors have
suggested molecular mechanisms involved in this process that may involve the
number of nuclei in the muscle cells (“myonuclear domain”) [12] and/or
epigenetic changes in the muscle cells [13].
With the limitation on access to large equipment and a variety of
weights and dumbbells, it is necessary to seek valid alternatives for
maintaining physical fitness and mitigating the deleterious effects of
detraining during this temporary period. These issues are presented and
discussed in the following sections.
Resistance
training with low loads
It is common, even in textbooks and technical/scientific position stands
on strength and conditioning, to recommend strength exercises with a load
equivalent to 6-12 repetitions to optimize muscle hypertrophy [14,15]. This
idea, however, has been questioned and new studies have brought to light new
possibilities. An investigation published in 2010 by Burd
et al. [16] was important for breaking this paradigm. Fifteen active men
performed 4 sets of knee extension with 3 load/repetition schemes: 1) 90% of
1RM until concentric failure; 2) 30% of 1 RM with volume equalized to the
previous condition (without reaching volitional failure); and 3) 30% of 1RM
until concentric failure. The authors measured muscle protein synthesis rates
before and after 4 and 24 hours of the resistance exercise session. It was
demonstrated that myofibrillar protein synthesis was elevated after 4 hours in
the condition 30% and 90% of 1RM until failure, but only with 30% of 1RM until
concentric failure after 24 h. Cell signaling proteins involved in protein
synthesis (Akt/mTOR pathway) were activated in all
conditions when compared to the resting situation.
Burd et al.
[16] investigated the acute response of muscle protein synthesis in response to
a session of resistance exercise. However, the chronic effects of resistance
training at different intensities and its effects on skeletal muscle
hypertrophy were still to be determined. To fill this gap, the same research
group evaluated the effects of a 12-week strength training program using 75-90%
of 1RM or 30-50% of 1RM on muscle hypertrophy and strength, with all series
being performed until the concentric failure. Fat free mass and cross-sectional
area of muscle fibers increased significantly in response to training, with no
differences between conditions. Muscular strength measured as 1RM load also
increased significantly in both conditions without differences between them,
except for the bench press exercise, where it was superior in the high load
group. The results of subsequent investigations [17-20] and the meta-analysis
conducted by Schoenfeld et al. [21] allow us to conclude that while the use of
high loads (> 70% of 1RM) seems to promote a superior stimulus for strength
gains, the same cannot be said about skeletal muscle hypertrophy.
The necessity or not to perform resistance exercise sets until the
concentric failure was also investigated. Concentric failure can be defined as
the inability to perform correctly an additional repetition of a given
exercise. If the practitioner is not able to continue performing a exercise without external assistance or without the
correct form, he has reached the concentric failure. In the fitness and
bodybuilding circles, it is a common sense that to maximize adaptations to
training, that is to maximize gains in strength and muscle hypertrophy, it
would be necessary to perform resistance exercises until concentric failure.
But do scientific studies corroborate this statement?
A systematic review with meta-analysis conducted by Davies et al.
[22] included 8 studies that addressed this issue and concluded that, to
maximize gains in muscle strength, it does not seem necessary. Such a
meta-analysis did not evaluate muscle hypertrophy, but as pointed out by
Schoenfeld and Grgic [23], performing sets until
concentric failure can be part of a training program, however they are not
necessary to optimize the hypertrophic response. Additionally, they also
emphasize that especially when training at high weekly frequency (4 or more
days), the inclusion of exercises performed until failure can have a negative
impact on impairing recovery between training sessions. In fact, one of the
deleterious effects to perform all sets until the concentric failure is the
total session volume reduction (and consequently the total weekly volume), when
compared to a set that the individual finishes before reaching failure [24,25].
While most of the studies assessing training to failure or not used
higher loads, generally greater than 70% of 1RM, recent studies have deepened
the investigation with other loading schemes. In order to determine whether
sets should be performed up to the concentric failure to promote muscle
hypertrophy with the use of low loads, Lasevicus et
al. [17] investigated 25 untrained men performing 8 weeks of a resistance
exercise program in four different conditions: low loads with or without
concentric failure (~34.4 and ~19.6 repetitions per set, respectively) and high
loads with or without concentric failure (~12.4 and ~6.7 repetitions per set,
respectively). The results showed that although maximum strength increased
significantly only with the use of high loads, quadriceps muscle hypertrophy
was similar between conditions, but only when low loads sets were performed
until the concentric failure. The study employed individuals with no experience
in strength training, but other studies corroborate these findings in trained
individuals [20,26].
In conclusion, when using low loads (30-60% 1RM), performing sets to
concentric failure seems to be necessary to improve strength and increase
muscle mass. When high loads are used, however, high-threshold motor units are
already recruited, and training to failure does not appear to bring an
additional benefit [23,27]. In fact, with high loads the failure can even be
counterproductive, since it can result in a total training volume reduction,
greater fatigue, necessity for longer recovery time between training sessions
and even higher risk for the development of overtraining [23-25].
Resistance
training using the body weight and elastic bands
At home, in general, access to training equipment or to a variety of
weights and heavy dumbbells is limited. Thus, the use of light loads with
dumbbells, exercises using the body weight, elastic bands or household items
can be a valid alternative to generate resistance in a strength training
program. For example, Kikuchi and Nakazato [28]
evaluated the effects of a resistance training program for 8 weeks with a
frequency of 2 days / week using exercise with their own body weight (push-ups)
with a load equivalent to 40% of 1RM on muscle strength and hypertrophy. The
training with body weight protocol resulted in a significant increase in
strength and thickness of the pectoris and triceps muscles at the same
magnitude as observed when bench press was performed using the same relative
intensity.
Elastic bands are often used in
conjunction with weights and dumbbells in the so-called training with variable
resistance [29]. Such method is based on the use of elastic bands to alter the
external resistance during the exercise at the entire range of motion [30]. The
use of elastic bands alone has also been studied, but mainly in more vulnerable
populations, such as the elderly or patients in a hospital environment [31-33].
For example, Orange et al. [34] demonstrated that 4 weeks of a resistance
training program using elastic bands and exercises with body weight with a
weekly frequency of 3 days resulted in increased functional capacity in middle-aged
men. However, studies that evaluated the effects of training using only elastic
bands in healthy young adults, athletes or not, are scarcer.
A study with young female handball players evaluated the effect of a
training program using elastic bands for 9 weeks, with a weekly frequency of 3
days/week [35]. The program consisted of 6 exercises involving trunk and lower
and upper limbs, performed at 3 sets of 6 to 10 repetitions per exercise, with
high execution speed. Power, pitch speed and agility were significantly
improved at the end of the training period. Similarly, Mascarin
et al. [36] demonstrated that strength training using elastic bands for
6 weeks during the pre-season in handball athletes resulted in improved muscle
power and throwing performance. Buskard et al.
[37] developed a method to determine the optimal training load with elastic
bands, in order to be used for athletes in the development of muscle power. The
authors concluded that its use can be adopted by coaches to improve athletes’
muscular power, especially when the use of free weights and training equipment
is limited.
Therefore, although limited studies have evaluated the effects of
exercises using the body weight or elastic bands in healthy young adults, such
strategy seems to be effective in mitigating or preventing the deleterious
effects of detraining when the access to free weights, dumbbells and strength
training equipment is limited.
Further
considerations
Training frequency is an important variable in every strength training
program. Studies have been carried out to determine whether there is an ideal
weekly frequency to maximize gains in strength and muscle hypertrophy, as
summarized in recent meta-analyzes [38,39]. In general, there seems to be no
differences for muscle hypertrophy when total weekly training volume is
equalized. In other words, the effects of performing 30 sets of a given muscle group in a week divided into 2 or 3 days of
training (15 and 10 sets per session, respectively), seems to promote the same
adaptations. It is important, however, to emphasize that performing a high
training volume in one session will require longer recovery periods. Therefore,
it may be more feasible to increase weekly frequencies, rather than increase
the number of sets per session in order to promote a higher weekly training
volume. Regarding muscle strength, higher training frequencies seem to be
associated with greater gains, especially in younger individuals [38].
Considering the limitation of space and training equipment for physical
exercise, we recommend the adoption of high training frequency (>5
times/week) during the period of social distancing, alternating with aerobic
exercises whenever possible, and with domestic and leisure activities involving
the movement of the whole body.
During the current COVID-19 pandemic contact among people should be
avoided. Thus, face-to-face guidance by training professionals is not possible.
However, whenever necessary and especially for beginners with no previous
training experience, it is recommended alternatives for physical exercise
prescription with no close contact between coach and clients. A study with
middle-aged adults (average of 53.6 years) demonstrated that there were no
differences in the effects of a home-based physical training program with or
without in person supervision [34]. It is important to note that the
unsupervised group received face-to-face instructions for carrying out the
prescribed exercises at the beginning of the intervention. Remote monitoring of
practitioners who have the basic knowledge of resistance exercises can be a
valid alternative and should be encouraged when the professional face-to-face
intervention is not possible.
General
recommendations
Based on the discussion above, we now address general recommendations
for home-based strength training:
Acknowledgements
The authors are thankful to the Espírito Santo
Research Foundation (nº 84417625/2018). Funding had no influence on the
preparation and publication of the current manuscript.