The effects of the COVID-19 lockdown in handball players

Abstract

The aim of this research was to analyse the capacity of a home-based training programme to
preserve aerobic capacity and jumping performance in top-level handball players during the COVID-19 lockdown.
Eleven top-level male handball players from the same team participated in the study. A submaximal shuttle run
test and a counter-movement jump test were used to measure the players’ aerobic fitness and lower limb
explosive strength, respectively. A 9-week home-based training programme was followed during lockdown.
Pre-test measurements were assessed before the pandemic on 29 January 2020 and ended on 18 May 2020.
Moderate significant mean heart rate increases were found in the late stages of the submaximal shuttle run
test after the lockdown (stage 5, 8.6%, P = 0.015; ES = 0.873; stage 6, 7.7%, P = 0.020; ES = 0.886; stage
7, 6.4%, P = 0.019; ES = 0.827). Moderate significant blood lactate increases were observed immediately
after the submaximal shuttle run test following the lockdown (30.1%, P = 0.016; ES = 0.670). In contrast, no
changes were found in jump performance. A structured home-based training programme during the
COVID-19 lockdown preserved lower limb explosive strength but was an insufficient stimulus to maintain aerobic
capacity in top-level handball players.

Full text

Biology of Sport, Vol. 38 No4, 2021 753
The effects of the COVID-19 lockdown in handball players
INTRODUCTION
The rst cases of coronavirus disease 2019(COVID-19, caused by
SARS-CoV-2) were detected in Wuhan, China, at the end of 2019[1].
Subsequently, due to the effects of the virus and its easy spread,
different countries opted to quarantine and isolate their citizens,
conning them to their homes. In Spain, astate of alarm was declared
on 15March, which affected the entire population[2]. At the sport-
ing level, all territorial, national and international competitions were
suspended. In handball, the last matches were played on 7and
8March 2020and all players had to stay at home at least until
4May 2020[3]. The different competitions did not resume again
until August 2020and only for elite teams (national and European
competitions).
The importance in handball of certain levels of strength, speed
and aerobic endurance to withstand training and competition is well
known[4,5,6,7]. It is also true that high intensity work is increas-
ingly important due to the increase in the number of possessions in
the game and the pace of play[5].
The effects of COVID-19lockdown on jumping performance
and aerobic capacity in elite handball players
AUTHORS: Roger Font1,2,3, Alfredo Irurtia4,5, Jose Antonio Gutierrez6, Sebastià Salas6, Enric Vila6,
Gerard Carmona3
1 Sport Performance Area FC Barcelona, Barcelona, Spain
2 National Institute of Physical Education of Catalonia (INEFC), University of Barcelona (UB), Barcelona, Spain
3 School of Health Sciences, Tecnocampus, Pompeu Fabra University, Mataró, Spain
4 INEFC-Barcelona Sport Sciences Research Group, National Institute of Physical Education of Catalonia (INEFC),
University of Barcelona (UB), Barcelona, Spain
5 Catalan School of Kinanthropometry, National Institute of Physical Education of Catalonia (INEFC), University
of Barcelona (UB), Barcelona, Spain
6 Medical Services FC Barcelona, Barcelona, Spain
ABSTRACT: The aim of this research was to analyse the capacity of ahome-based training programme to
preserve aerobic capacity and jumping performance in top-level handball players during the COVID-19lockdown.
Eleven top-level male handball players from the same team participated in the study. Asubmaximal shuttle run
test and a counter-movement jump test were used to measure the players’ aerobic tness and lower limb
explosive strength, respectively. A 9-week home-based training programme was followed during lockdown.
Pre-test measurements were assessed before the pandemic on 29January 2020and ended on 18May 2020.
Moderate signicant mean heart rate increases were found in the late stages of the submaximal shuttle run
test after the lockdown (stage 5, 8.6%,
P
=0.015; ES=0.873; stage 6, 7.7%,
P
=0.020; ES=0.886; stage
7, 6.4%,
P
=0.019; ES=0.827). Moderate signicant blood lactate increases were observed immediately
after the submaximal shuttle run test following the lockdown (30.1%,
P
=0.016; ES=0.670). In contrast, no
changes were found in jump performance. A structured home-based training programme during the
COVID-19lockdown preserved lower limb explosive strength but was an insufcient stimulus to maintain aerobic
capacity in top-level handball players.
CITATION: Font R, Irurtia A,Gutierrez JA et al. The effects of COVID-19 lockdown on jumping performance
and aerobic capacity in elite handball players. Biol Sport. 2021;38(4):753
–
759.
Received: 2021-07-29; Reviewed: 2021-09-18; Re-submitted: 2021-09-26; Accepted: 2021-09-26; Published: 2021-10-16.
During this entire period of home connement, the players had to
work in their respective homes to avoid partially or totally losing
previously acquired morphological and physiological adaptations
through detraining or adecrease in training[8,9,10,11,12]. The
difculties of nding optimal spaces to train or having adequate train-
ing material and the uncertainty as to when competitions would resume
generated frustration and demotivation in many athletes during this
period[13]. Individualized work routines were planned to reduce this
training handicap as much as possible, and to counter lack of motiva-
tion, poor nutrition and resting issues that may affect the athletes’
ability to maintain proper habits and routines[10,14,15,16]. In
many cases material was provided to the players and group sessions
were held by videoconference[10,17].
Most of the current research on detraining is characterized by
much shorter periods of time than that of this pandemic[11,12].
However, there is alack of information regarding the capacity of
home training programmes to preserve general tness levels (lower
Original Paper
DOI: https://doi.org/10.5114/biolsport.2021.109952
Key words:
Elite team sports
Detraining
Heart rate
Lactate
Pandemic
Jumping
Corresponding author:
Roger Font Ribas
Sport Performance Area FC
Barcelona
Av. Onze de Setembre, s/n
08970Sant Joan Despí
Barcelona, Spain
Ciudad Deportiva Joan Gamper
E-mail: roger.font@fcbarcelona.cat

754
Roger Font Ribas et al.
During the test, heart rate (HR) was registered using aGarmin
HR strap. The HR monitor was linked to the WIMU PRO system
(Realtrack Systems, S.L., Almeria, Spain) and data were analysed
thereafter using mean HR values for each submaximal shuttle run
test stage.
One minute after the end of the test, players were pricked in the
earlobe to analyse blood lactate levels[20,21,22]. The analysis
was performed with aLactate Scout + lactate analyser and Lactate
Scout test strips (Nova Biomedical, Waltham, MA, USA).
Jump
The CMJ test was used to assess vertical jump performance as an
indicator of lower limb explosive strength[23]. Players performed
afast exion movement of the knee joint followed by amaximum-
effort vertical jump, maintaining the hands-on-hips position until the
nal phase of the jump. Acontact platform (Chronojump Boscosys-
tem, Barcelona, Spain) was used to assess CMJ height. The hardware
was connected to acomputer which displayed the vertical jump
height (cm) using free software (2.0.2., Chronojump Boscosystem
Software, Barcelona, Spain). This type of technology has proven its
reliability and validity in other types of research with vertical jump
tests[24]. Players performed two bilateral CMJs and two unilateral
CMJs with each leg. The best result of each test (height, cm) was
recorded and used for further analysis.
Home training programme during COVID-19lockdown
Each week during connement, players received astructured training
programme to follow at home. Basically, the home-based training
programme consisted of ve training days, from Monday to Friday,
with abreak over the weekend. During the rst eight weeks, three
strength training sessions were performed per week (onMondays,
Wednesdays, and Fridays) and two endurance-oriented sessions
(onTuesdays and Thursdays). During the last week (week 9), two
strength training sessions and ve endurance sessions (three outdoor
running sessions and two stationary bike sessions at home) were
performed. There was around a40% reduction in workload volume
between what the players actually did at home during the
COVID-19lockdown and what they would have performed under
normal training and competition.
During connement, players performed an average of 27strength
training sessions, including both individual sessions and online group
sessions. All sessions conducted at home followed the medical recom-
mendations derived from the COVID-19pandemic[9,25]. All sessions
were preceded by ageneral warm up consisting of ~10min of low
intensity cycling (stationary bike), mobility and lumbo-pelvic stability
exercises. In the rst four weeks, strength training was endurance-
oriented and over the last four weeks strength training was hypertro-
phy-oriented[26]. Individual hypertrophy-oriented training programmes
were organized in super-sets in which acombination of low specic-
ity level exercises (i.e., bilateral squat-based exercises) preceded
slightly more specic exercises (more dynamic correspondence with
limb explosive strength and aerobic capacity) in top handball players
during the COVID-19lockdown. To the best of our knowledge, only
one previous study[14] has investigated the effects of agiven train-
ing programme in the aerobic capacity of elite handball players. Such
studies might provide valuable insights about the real impact of home
training programmes to prevent detrimental effects on the general
tness of elite handball players.
Accordingly, the aim of this research was to analyse the effective-
ness of ahome training programme to preserve aerobic capacity and
lower limb explosive strength in top-level handball players during the
COVID-19lockdown.
MATERIALS AND METHODS
Design
Aretrospective design was used to compare the change in submaxi-
mal shuttle run test and jump test performance. A9-week home-based
training programme was followed during lockdown. Pre-test measure-
ments were assessed before the pandemic on 29January 2020and
ended on 18May 2020. The tests were conducted on the same day,
rst performing the submaximal shuttle run test in two groups of ve
and six players, respectively, and then the counter-movement jump
(CMJ) test. The submaximal shuttle run and the CMJ tests were used
to measure the players’ aerobic tness and lower limb explosive
strength (both bilateral and unilateral), respectively.
Subjects
The study was conducted on 11top-level male professional handball
players from the same team throughout the same season. These
were all international players with their respective national teams
during the season in which they participated in this study. The play-
ers were three wings (26.3±3.7 years; 185.3 ± 4.7 cm;
83.2±6.5kg), four backs (29.5±7.0years; 193.3±5.1cm;
98.3±7.4kg), three line players (27.9±6.4years; 195.0±3.0cm;
105.3±9.2kg) and one goalkeeper (27.9±0years; 190.0±0cm;
84.0±0kg). The data were obtained from the periodic monitoring
of the players during training sessions. All players signed acontrac-
tual clause accepting their participation in research projects; therefore
approval by an ethics committee was not required[18]. However,
all players were informed about the purpose of the study, the known
risks and possible associated hazards. The research was in accordance
with the Declaration of Helsinki, and professional players gave in-
formed consent prior to participation through their contracts.
Submaximal shuttle run test
To assess the aerobic capacity of the players, the multistage 20-me-
tre shuttle run test[19] was performed up to stage number 8. The
test consisted of running continuously between two lines placed
20mapart at running speeds increased by appropriate intervals at
apre-recorded beep. Mean velocity started at 8.5km · h-1 for the
rst minute (stage 1), increasing by 0.5km · h-1 every minute up to
12km · h-1 (stage 8).

Biology of Sport, Vol. 38 No4, 2021
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The effects of the COVID-19 lockdown in handball players
handball-specic movements, i.e., vertical jump exercises)[26]. Re-
garding endurance training, players performed an average of 19ses-
sions. In the rst four weeks, players performed individual strength-
based high-intensity interval training (HIIT) circuits, and from the fth
week onwards they were prescribed general aerobic tness training
sessions based on continuous and progressive exercises. Both subjec-
tive ratings of perceived exertion (RPE)[27,28] and the OMNI Per-
ceived Exertion Scale (OMNI-Res Scale) for Resistance Exercise[29]
were used to prescribe intensity during training sessions. See Fig-
ure1for acomplete overview of the basic characteristics of the home-
based training programme.
Statistics
Data were tested for approximation to anormal distribution using
the Shapiro–Wilk test. Apaired Student’s t-test was used to evaluate
differences in variables of interest (body mass, mean heart rate,
capillary blood lactate concentration, CMJ height) from pre- and
post-lockdown periods. Cohen’s dwas used to calculate the effect
size (ES). Thresholds for ES statistics were trivial (ES<0.20); small
(0.20<ES<0.59); moderate (0.60 < ES <1.19); large
(1.20<ES<1.99); and very large (ES >2.0)[30]. All data were
reported as mean±standard deviation and the level of signicance
was set at P<0.05. All statistical analyses were conducted using
SPSS version 23.0(SPSS Statistics, IBM Corp., Armonk, NY, USA).
RESULTS
No signicant differences (ES=-0.036, trivial) were found in body
mass following the home training programme (Pre-lockdown:
99.0±12.4kg and Post-lockdown: 98.6±12.7kg).
Submaximal shuttle run test
Moderate, non-signicant mean HR increases were observed in the
early stages of the submaximal shuttle run test (aerobic capacity)
(from stage 1, 108±15and 117±11bpm; stage 2, 127±11and
141±21bpm; stage 3, 133±12and 147±20bpm; stage 4,
140±12and 153±19bpm of HR mean values from before and
after the home training programme, respectively) and moderate,
signicant changes were observed in later stages (from stage 5,
FIG. 1. Home training programme overview. BW, body weight; HIIT, high-intensity interval training; OMNI-Res Scale, Perceived
Exertion Scale for Resistance Exercise; RPE, rating of perceived exertion.

756
Roger Font Ribas et al.
(seeFigure2). This might be indicative of aloss of aerobic capaci-
ty[31,32]. It has been well established that detraining, due to
training suppression or inadequate training, induces maximum HR
increases (between 5% and 10%)[11]. Although this was not ex-
actly the case during the lockdown scenario, the home training pro-
grammes probably failed to provide asufcient stimulus to maintain
aerobic capacity in elite handball players. This was also previously
described by Fikenzer etal.[14], who found that endurance capac-
ity, measured by the maximum mean velocity achieved in amultistage
20-metre shuttle run test, was diminished in most elite handball
players from agiven team due to the unspecic and inadequate
stimuli provided by ahome-based training programme during the
COVID-19lockdown. Dauty etal.[32] obtained similar results with
the yo-yo test in young football players. The dependence on volume
of endurance training responses[33] would explain the incapacity
of home training programmes to maintain aerobic capacity in highly
trained top handball players. In fact, the home training volumes were
approximately 40% lower than those achieved during the regular
season immediately before the lockdown. Moreover, our players only
received running-specic stimuli during the last two weeks of the
lockdown (seeFigure1), reinforcing the notion that the lack of train-
ing specicity also contributed, to some extent, to the loss of aerobic
capacity[14,32].
The moderate, significant increases in lactate after the
COVID-19lockdown were also indicative of adecrease in the players’
aerobic capacity (seeFigure3)[11,34]. Specically, lactate increas-
es are indicative of areduction in the oxidative capacity of the
145±13and 158±15bpm[P=0.015]; stage 6, 152±12and
164 ± 14 bpm [P = 0.020]; stage 7, 157± 11 and
167±13bpm[P=0.019] of HR mean values from before and
after the home training programme, respectively) (seeFigure2).
Finally, only small, non-signicant increases were found in the last
stage (stage 8, 163±10and 168±13bpm of HR mean values
from before and after the home training programme, respectively).
The results from this test were derived from 9players due to HR
band registration problems with 2of the players from the sample.
Regarding lactate, moderate, signicant increases (4.1±1.4and
5.3±2.2[P=0.016] mmol/L mean values from before and after
the home training programme, respectively) were found (seeFigure3).
Jump test
No changes were found in jump performance (41.8±8.3and
41.0±7.0cm of bilateral CMJ, 20.9±7.3and 22.3±4.7cm
of unilateral CMJ[right], and 21.7±4.4and 22.4±3.2cm of
unilateral CMJ[left] height from before and after the home training
programme, respectively) (seeFigure4).
DISCUSSION
The aim of this research was to analyse the ability of ahome train-
ing programme to preserve aerobic capacity and jumping performance
in top-level handball players during the COVID-19lockdown. The
home training programmes followed by the players maintained
lower limb explosive strength, measured as CMJ performance (jump
height), but appeared to be insufcient to maintain aerobic capacity.
Aerobic capacity
Moderate, signicant HR increases were observed in the last stages
of the submaximal shuttle run test after the COVID-19lockdown
FIG. 2. Mean heart rate values from each multistage 20-metre
shuttle run test. Black circles, pre-lockdown; White circles, post-
lockdown. ES, Cohen’s d effect size. *Signicantly different at
P<0.05.
FIG. 3. Capillary blood lactate concentration. Black circles, pre-
lockdown (Pre); White circles, post-lockdown (Post). ES, Cohen’s
deffect size. *Signicantly different at P<0.05.

Biology of Sport, Vol. 38 No4, 2021
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The effects of the COVID-19 lockdown in handball players
FIG. 4. Counter movement jump (CMJ) height. Black circles, pre-lockdown (Pre); White circles, post-lockdown (Post). ES, Cohen’s
deffect size.
muscle[11] and present ahigh correlation with endurance capacity
in trained populations[35]. Together with HR values, these results
conrmed that home-based endurance training was insufcient to
maintain aerobic tness in top-level handball players. However, it
must be considered that since only moderate (ES) changes in aerobic
tness indicators (HRand lactate) were found after the lockdown, it
seems reasonable to expect arapid recovery of pre-lockdown values
when players returned to on-court sport-contextualized training re-
gimes.
Lower limb explosive strength
Regarding CMJ performance as an indicator of lower limb explosive
strength[23], no changes were found between the two test periods
(seeFigure4), showing that the training stimuli provided by the strength
home-based training programme (Figure1) were adequate to preserve
jump capacity. Despite certain signs of detraining in neuromuscular-
related qualities and peak power output, similar results have been
previously reported in the literature about home training programmes’
capacity to preserve jump performance (height) in professional football

758
Roger Font Ribas et al.
players[36,37] and futsal players[38]. Specically, Rampinini
etal.[37] analysed fty professional football players and found that
2–3bodyweight or small weight strength training sessions per week
at home during the COVID-19lockdown preserved CMJ height despite
amoderate (ES) loss in peak power output. Those authors[37] also
obtained similar results following the transition period, where similar
bodyweight training strategies were implemented. In this regard, it
has also been observed in national level handball players that a7-week
interruption of the external weight-based strength training, where
players only performed sport-specic training and bodyweight exer-
cises, was enough to maintain jump performance (height)[39]. There-
fore, and although acertain degree of loss in jump-related neuromus-
cular qualities might be expected, home-based lower limb strength
training programmes, despite the differences in training contents and
strategies (including equipment), seem to be capable of maintaining
jump performance measured as CMJ height.
Limitations
An important limitation of this study was the impossibility of assess-
ing the whole team after the lockdown because many players were
in their respective home countries. Despite this limitation, 11top-
level handball players were analysed, all of whom were interna-
tional players with their respective national teams. Finally, since the
ndings of this study come from 11high-level handball players from
asingle team, caution is advised when generalising from these results,
as different home training strategies in different team sport athletes
might induce different adaptations.
Practical applications
Astructured home-based training programme based on body weight
and low weight exercises provides asufcient stimulus to maintain
jump performance (jumping height), an indicator of lower limb ex-
plosive strength, in top-level handball players. In contrast, the home-
based training programme described did not succeed in preserving
aerobic tness in the cohort under study. Earlier implementation of
aerobic tness training strategies might have helped in the preserva-
tion of players’ endurance capacity. However, since the loss in aero-
bic tness indicators was moderate (ES), arapid recovery of pre-
lockdown values may be expected when players return to on-court
sport-contextualized training regimes. Overall, the results of this study
support existing general recommendations on the training approach
during COVID-19lockdown periods[40].
CONCLUSIONS
In conclusion, astructured home-based training programme during
the COVID-19lockdown preserved lower limb explosive strength but
was an insufcient stimulus to maintain endurance capacity in top-
level handball players.
Acknowledgements
The authors would like to thank the players who participated in this
study, the coaching staff and medical services of FC Barcelona and
the FC Barcelona Performance Department for giving us the oppor-
tunity to carry out this study.
Disclosure statement
The authors declare no potential conicts of interest.
Conict of interest declaration
The authors declare no potential conict of interest.
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