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medicina
Article
Effects of 4-Week Inspiratory Muscle Training on Sport
Performance in College 800-Meter Track Runners
Yun-Chi Chang 1,2, Hsiao-Yun Chang 3, Chien-Chang Ho 2,4 , Po-Fu Lee 2,5 , Yi-Chen Chou 6, Mei-Wun Tsai 1
and Li-Wei Chou 1,*
Citation: Chang, Y.-C.; Chang, H.-Y.;
Ho, C.-C.; Lee, P.-F.; Chou, Y.-C.; Tsai,
M.-W.; Chou, L.-W. Effects of 4-Week
Inspiratory Muscle Training on Sport
Performance in College 800-Meter
Track Runners. Medicina 2021,57, 72.
https://doi.org/10.3390/
medicina57010072
Received: 4 December 2020
Accepted: 12 January 2021
Published: 15 January 2021
Publisher’s Note: MDPI stays neu-
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tribution (CC BY) license (https://
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4.0/).
1Department of Physical Therapy and Assistive Technology, National Yang-Ming University,
Taipei 112, Taiwan; james76630@gmail.com (Y.-C.C.); tmwk@ym.edu.tw (M.-W.T.)
2Department of Physical Education, Fu Jen Catholic University, New Taipei City 242, Taiwan;
093703@mail.fju.edu.tw (C.-C.H.); f520184fred@yahoo.com.tw (P.-F.L.)
3Department of Athletic Training and Health, National Taiwan Sport University, Taoyuan 333, Taiwan;
yun1130@ntsu.edu.tw
4Research and Development Center for Physical Education, Health, and Information Technology,
Fu Jen Catholic University, New Taipei City 242, Taiwan
5Graduate Institute of Sport Coaching Science, Chinese Culture University, Taipei 111, Taiwan
6Physical Education Office, National Tsing Hua University, Hsinchu City 300, Taiwan;
a0925701007@yahoo.com.tw
*Correspondence: lwchou@ym.edu.tw
Abstract:
Background and objectives: Respiratory muscle fatigue is one of the important factors limiting
sports performance due to the metaboreflex. This reflex will cause a decrease in blood flow to the
extremities and accelerate exercising limb fatigue. Previous studies found that inspiratory muscle
training (IMT) can effectively enhance the respiratory muscle endurance and reduce fatigue during
long-duration exercise or aerobic exercise, thereby enhancing athletic performance. However, the
mechanism between inspiratory muscle strength, change of limb blood flow and sports performance
still requires investigation, especially in short-duration exercise, anaerobic or both aerobic and
anaerobic exercise. The purpose of this study was to investigate the effects of 4-week inspiratory
muscle training on respiratory muscle strength, limb blood flow change rate and sports performance
in recreational 800-m college runners. Materials and Methods: Twenty healthy 800-m college runners
randomized into the IMT group (11 subjects) and control group (9 subjects). IMT consisted of 30
inspiratory efforts twice daily, 5 days a week, with intensity at 50%, 60%, 70% and 80% of maximum
inspiratory pressure (MIP) for 4 weeks, while a control group kept 50% of MIP for 4 weeks. An 800-m
trial test, limb blood flow change rate by using Impedance Plethysmography, and MIP were as the
outcome measured variables and be evaluated. All measured variables were assessed before and
after 4-week IMT training. Two-way ANOVA was conducted for statistical analysis. Results: The
results showed significantly interaction between groups and pre-posttest. IMT group significantly
decreased limb blood flow change rate from 19.91
±
11.65% to 9.63
±
7.62% after received the
IMT training program (p< 0.05). The MIP significantly improved from 112.95
±
27.13 cmH
2
O to
131.09
±
28.20 cm H
2
O in IMT group, and the 800-m trial test also shorted the running time from
162.97
±
24.96 s to 156.75
±
20.73 s. But the control group no significantly changed in MIP and 800-m
trial test. Conclusions: Our results indicated that the 4-week IMT training (twice a day, 5 days a week)
significantly improves participants’ inspiratory muscle strength, 800-m running performance and
decreases the limb blood flow change rate.
Keywords: respiratory muscle capability; athletic performance; muscle fatigue
1. Introduction
Jogging has become one of the popular activities and aerobic exercise in the worldwide
recently. As an aerobic-based exercise, cardiopulmonary endurance and respiratory muscle
Medicina 2021,57, 72. https://doi.org/10.3390/medicina57010072 https://www.mdpi.com/journal/medicina
Medicina 2021,57, 72 2 of 8
strength are fundamentally required and should develop to enhance cardiorespiratory
health. The diaphragm, one of the respiratory muscles, is essential to and functions as the
skeletal muscles for respiratory movement [
1
,
2
]. While individuals engage in high-intensity
exercise or experience a period of effort, the fatigue of respiratory muscles will reflexly
increase sympathetic vasoconstrictor activity and vasoconstriction of the vasculature of
the exercising limb, as a result, blood flow cannot reach the muscles of the limbs [
3
–
6
].
Therefore, insufficient blood flow in limbs decreases the oxygen exchange rate and increases
the feelings of soreness and discomfort, thereby affecting their sports performance.
According previous studies, during constant-load exercise, the work of respiratory
muscle was reduced about 60% by proportional assisting ventilation, and end-exercise
quadriceps fatigue decreased by 25–30% compared with the control group [
7
]. Furthermore,
during constant-load leg cycling (adding supplemental O2 to the inspired air), when
exercise-induced arterial desaturation was prevented, it was found that quadriceps fatigue
was nearly 50% less compared with the control group [
8
]. Thus, training for the respiratory
muscles may extend the period of fatigue, thereby improving sports performance, balance
of arterial blood, gas and acid–base [9].
From the athletic perspective, previous studies have indicated that inspiratory muscle
training (IMT) significantly reduces fatigue and improves athletic performance. Johnson
and colleagues [
10
] used the threshold IMT (PowerBreathe
®®
) (POWERbreathe Interna-
tional Ltd., England, UK) intervention for 6 weeks on cyclists. Their results indicated that
after six weeks of training, the endurance the continuous power output increased and
cycling performance improved. The same results were found in Romer and colleagues’
work [
11
]. In this study, sixteen trained cyclists were randomly assigned into IMT group
and sham IMP group and received 6-week IMT training. The pulmonary function and 20
and 40 km time-trial performance were measured. The result improved the 20 and 40 km
time-trial performance and pulmonary function. Kilding et al. also investigated the IMT
effect on 16 competitive club-level swimmers. Their results also are similar those previous
studies. Their results indicated that decreased the timing in the 100 m swim by 1.7% and in
200 m swim by 1.5% [
12
]. In addition, Volianitis and colleagues [
13
] conducted an 11-week
of threshold IMT (PowerBreathe
®®
) on elite female rowers. Their results of the maximum
inspiratory pressure in the IMT group were significantly higher than in the control group.
It can be seen that IMT can improve respiratory muscle strength and sports performance.
In past studies, the exercises for respiratory muscle training included running, swim-
ming, and cycling [
14
–
16
]. Most of them focused on long-distance and aerobic exercise.
However, there were fewer studies on respiratory muscle training for middle-distance and
short-distance sports. Middle-distance running events include 800 m and 1500 m. The
800-m and 1500 m distance are the sport that includes both aerobic and anaerobic exercise
event. A study for 1500 m runners has proved that respiratory muscle training can increase
respiratory muscle strength and improve athletic performance [
15
]. However, the distance
of 800 m is shorter than the distance of 1500 m. In terms of exercise physiology, it tends
to more anaerobic exercise [
1
,
2
,
14
]. It is doubtful whether the effect of respiratory muscle
training is as same as 1500 m distance.
However, previous studies related IMT effect have focus on long-duration exercise.
Few studies investigate the effect of IMT on shorter distance sports, like 800-m distance
run. Brown and Kilding found that the occurrence of inspiratory muscle fatigue after
a short-duration front crawl swim exercise [
14
]. Ohya et al. also reported that shorter-
duration running exercise would induce inspiratory muscle fatigue [
17
]. Therefore, there
is a need to better understand whether respiratory muscle training is helpful for middle
distance events, like 800-m distance run. Further investigation is still needed to stablish
the possible mechanism. Hence, the purpose of the study was to investigate the effects of
4-week inspiratory muscle training on respiratory muscle strength, limb blood flow change
rate and sports performance in recreational college 800-m track runners. The research
hypothesis was 4-week inspiratory muscle training increased respiratory muscle strength,
decreased the limb blood flow change rate and improve 800-m sport performance.
Medicina 2021,57, 72 3 of 8
2. Materials and Methods
2.1. Study Design and Participants
This study was conducted with a two group compared, pre and post- test design. Ac-
cording to the basic statistical power requirement from a previous study [
18
], the minimum
number of subjects in each group should be at least 8. Finally, twenty-two recreational
800-m college runners from the track and field Team of the university were recruited. After
randomization of the IMT group and control group, two participants dropped out of the
control group. Participants were recruited by finding athletes who had trained at least
three times per week for a minimum of 60 min and were able to finish the full experi-
ment. Moreover, three exclusive criteria were applied: (1) present or past cardiovascular,
pulmonary and neurological disease; (2) smoker; (3) allergies to electro-conductive pads.
All participants were informed of the study procedure and signed the informed consent
form before the experiment. The present study was also approved by the Institutional
Review Board of China Medical University Hospital in Taiwan (CRREC-102-027, 17 June,
2014). Table 1presents the anthropological characteristics of the participants. No significant
difference was found between the IMT group and the control group.
Table 1. The detailed information of the participants (N= 20).
Anthropological
Information
IMT Group (N= 11)
Mean ±SD
Control Group (N= 9)
Mean ±SD p-Value
Gender (M:F) 8:3 6:3 0.10
Age, years 21.64 ±2.06 20.78 ±1.48 0.31
Height, cm 170.59 ±6.7 172.33 ±9.94 0.64
Weight, kg 61.46 ±6.92 63.39 ±14.33 0.69
Abbreviations: SD, standard deviation.
2.2. Procedure
Baseline data of the inspiratory muscle training (MIP) test, blood flow test and 800 m
time-trial test were collected from all participants before inspiratory muscle training in-
tervention. After Baseline data collection, all participants take a day’s rest, the training
group started a 4-week inspiratory muscle training and the control group started placebo
training. Both groups did the same skill training and weight training for 4 weeks. All
participants repeated data collection from MIP test, blood flow test, and 800 m time-trial
test immediately after 4-week IMT. The procedure flow list in Figure 1.
Medicina 2021, 57, x FOR PEER REVIEW 4 of 9
Figure 1. Experimental Procedure.
2.3. Measurements
2.3.1. Maximal Inspiratory Pressure (MIP) Assessment
The MIP assessment in the present study was measured by the MicroRPM (Micro
Medical/CareFusion, Kent, United Kingdom) with inserted the PUMA PC Software (Mi-
cro Medical, Kent, England) in the laptop. The PUMA PC software works with the Mi-
croRPM Respiratory Pressure Meter to measure respiratory muscle strength and calcu-
lated the MIP from the one-second average maximum pressure. During the test, the par-
ticipants should be sitting, then the investigator explained the MicroRPM device usage
procedure to the participants. When performed the MIP assessments, participants were
asked to exhale slowly and completely first with sealed lips around the mouthpiece, and
then inhale hard rapidly. The investigators record the data for the largest value which
show on the MicroRPM and its software. Participants were allowed to rest between each
trial for 1 min and were asked to repeat the protocol 5 times [19]. Accord to the previous
study, the MicroRPM reliably measured MIP [20].
2.3.2. Limb Blood Flow Assessment
Impedance Plethysmography RheoScreen compact (Medis, Ilmenau, Germany) was
used to evaluate limb blood flow. The device had been calibrated and guaranteed high
quality of the recorded signal, as well as high reproducibility [21]. The test used measure-
ment by a four-electrode technique. The two outer electrodes were used to apply the cur-
rent, and the two inner electrodes were used for delineating the quadriceps under meas-
urement (Figure 2).
To clearly assess limb blood flow change rate among the participants, every single
assessment was conducted 2 times and cooperated with the respiratory muscle fatigue
induction. After the first blood flow assessment, the participants were asked to breathe in,
maintaining 60% of inspiration pressure by the POWERbreathe respiratory training de-
vice. The intensity of the inspiration pressure was based on the MIP assessment, and the
time ratio of inspiration and expiration was 1:2. Participants were encouraged to maintain
their breath. Once the participant failed to maintain the inspiration pressure more than 2
times, the process was ended. Then, the lower limbs’ blood flow was immediately meas-
ured. The limb blood flow change rate were calculated the value of the second test minus
the value of the first test, then divided by the value of the first test, and multiplied by
100%.
22 subjects
(pre-test)
•MIP test
•blood flow test
•800-m time-
trial test
Randomlize to
•IMT Training group
(N=10)
•Control group (N=10)
•Two participated
drop out by
screening exclusive
criteria
4 weeks IMT
training
intervention
•IMT Training
group (intensity:
50%-60%-70%-
80% of MIP)
•Control group
(intensity:50% of
MIP)
20 subjects
(post-test)
•MIP test
•blood flow test
•800-m time-
trial test
Figure 1. Experimental Procedure.
2.3. Measurements
2.3.1. Maximal Inspiratory Pressure (MIP) Assessment
The MIP assessment in the present study was measured by the MicroRPM (Micro
Medical/CareFusion, Kent, United Kingdom) with inserted the PUMA PC Software (Micro
Medical, Kent, England) in the laptop. The PUMA PC software works with the MicroRPM
Medicina 2021,57, 72 4 of 8
Respiratory Pressure Meter to measure respiratory muscle strength and calculated the
MIP from the one-second average maximum pressure. During the test, the participants
should be sitting, then the investigator explained the MicroRPM device usage procedure
to the participants. When performed the MIP assessments, participants were asked to
exhale slowly and completely first with sealed lips around the mouthpiece, and then inhale
hard rapidly. The investigators record the data for the largest value which show on the
MicroRPM and its software. Participants were allowed to rest between each trial for 1 min
and were asked to repeat the protocol 5 times [
19
]. Accord to the previous study, the
MicroRPM reliably measured MIP [20].
2.3.2. Limb Blood Flow Assessment
Impedance Plethysmography RheoScreen compact (Medis, Ilmenau, Germany) was
used to evaluate limb blood flow. The device had been calibrated and guaranteed high qual-
ity of the recorded signal, as well as high reproducibility [
21
]. The test used measurement
by a four-electrode technique. The two outer electrodes were used to apply the current,
and the two inner electrodes were used for delineating the quadriceps under measurement
(Figure 2).
Medicina 2021, 57, x FOR PEER REVIEW 5 of 9
Figure 2. The location of electrodes (a) and equipment (b) during the limb blood flow measure-
ment.
2.3.3. Athletic Performance Assessment
An 800-m time trial test was used as the athletic performance assessment and was
carried out before and after four-week respiratory muscle training. According to studies
from Hanon et al. and Ohya et al., the 800-m track running created a state of imbalance
within the body, a decline in blood pH and the excessive functioning of certain compart-
ments, which leads the body to exhaustion and respiratory muscle fatigue [17,22]. There-
fore, this athletic performance test can be used as an outcome measured variable of the
effectiveness of respiratory muscle training. Before the 800-m time trial test, the partici-
pates warmed up for 5 min and then performed the test on the athletic track on campus.
During the test, they ran 800 m on the track and recorded the time with a timer.
2.4. Interventions of Respiratory Muscle Training
This study adopted a resistance-adjustable electronic respiratory training device
called POWERbreathe K2 (POWERbreathe International Ltd., England, UK) for the train-
ing intervention. Initially, the participants were asked to hold the disposable air nozzle
with their mouth and applied a nose clip to prevent ventilation through the nasal passage.
When the primary setting was done, the participants were allowed to start breathing fol-
lowing the signals from the device and the investigators. The device provided resistance
during inhalation while recording inspirational pressure. Participants were allowed to
discontinue instantly once they felt any discomfort.
This intervention was completed twice a day, 5 days a week for the IMT group. The
training intensity was progressively set at 50%, 60%, 70% and 80% of MIP for weeks 1, 2,
3 and 4, respectively. Further, the control group was required to keep at the level of 50%
MIP for 4 weeks.
2.5. Statistical Analyses
The Statistical Package for Social Sciences (SPSS 20, SPSS Inc., Chicago, IL, USA) soft-
ware was used for the statistical analysis. The participants’ anthropological information
was first described, with the independent sample t-test and chi-square test in order to
compare the group differences. The normality of variables was evaluated with the
Shapiro–Wilk test. Subsequently, two-way ANOVA was conducted for the pre- and post-
test results and group comparison. Data are presented as mean and standard deviation
for continuous variables and as ratios for nominal variables. A significance level of α =
0.05 was adopted
Figure 2.
The location of electrodes (
a
) and equipment (
b
) during the limb blood flow measurement.
To clearly assess limb blood flow change rate among the participants, every single
assessment was conducted 2 times and cooperated with the respiratory muscle fatigue
induction. After the first blood flow assessment, the participants were asked to breathe in,
maintaining 60% of inspiration pressure by the POWERbreathe respiratory training device.
The intensity of the inspiration pressure was based on the MIP assessment, and the time
ratio of inspiration and expiration was 1:2. Participants were encouraged to maintain their
breath. Once the participant failed to maintain the inspiration pressure more than 2 times,
the process was ended. Then, the lower limbs’ blood flow was immediately measured. The
limb blood flow change rate were calculated the value of the second test minus the value
of the first test, then divided by the value of the first test, and multiplied by 100%.
2.3.3. Athletic Performance Assessment
An 800-m time trial test was used as the athletic performance assessment and was car-
ried out before and after four-week respiratory muscle training. According to studies from
Hanon et al. and Ohya et al., the 800-m track running created a state of imbalance within
the body, a decline in blood pH and the excessive functioning of certain compartments,
which leads the body to exhaustion and respiratory muscle fatigue [
17
,
22
]. Therefore, this
athletic performance test can be used as an outcome measured variable of the effectiveness
of respiratory muscle training. Before the 800-m time trial test, the participates warmed
Medicina 2021,57, 72 5 of 8
up for 5 min and then performed the test on the athletic track on campus. During the test,
they ran 800 m on the track and recorded the time with a timer.
2.4. Interventions of Respiratory Muscle Training
This study adopted a resistance-adjustable electronic respiratory training device called
POWERbreathe K2 (POWERbreathe International Ltd., England, UK) for the training
intervention. Initially, the participants were asked to hold the disposable air nozzle with
their mouth and applied a nose clip to prevent ventilation through the nasal passage. When
the primary setting was done, the participants were allowed to start breathing following
the signals from the device and the investigators. The device provided resistance during
inhalation while recording inspirational pressure. Participants were allowed to discontinue
instantly once they felt any discomfort.
This intervention was completed twice a day, 5 days a week for the IMT group. The
training intensity was progressively set at 50%, 60%, 70% and 80% of MIP for weeks 1, 2, 3
and 4, respectively. Further, the control group was required to keep at the level of 50% MIP
for 4 weeks.
2.5. Statistical Analyses
The Statistical Package for Social Sciences (SPSS 20, SPSS Inc., Chicago, IL, USA)
software was used for the statistical analysis. The participants’ anthropological information
was first described, with the independent sample t-test and chi-square test in order to
compare the group differences. The normality of variables was evaluated with the Shapiro–
Wilk test. Subsequently, two-way ANOVA was conducted for the pre- and post-test results
and group comparison. Data are presented as mean and standard deviation for continuous
variables and as ratios for nominal variables. A significance level of
α
= 0.05 was adopted
3. Results
MIP, blood flow change rate and 800 m data were expressed as mean and standard
deviation (Table 2). Table 3shows the results of respiratory muscle training in the present
study. After a 4-week respiratory muscle training, all variables were found significantly
interaction effect between group and pre-post training (p< 0.05). This indicated that the
MIP significantly improved after 4-week respiratory muscle training.
Table 2.
The results of the MIP, blood flow change rate, and 800-m times trial test between IMT and
control group.
IMT * Group Control Group
Pre (N= 10)
(Mean ±SD)
Post (N= 10)
(Mean ±SD)
Pre (N= 10)
(Mean ±SD)
Post (N= 10)
(Mean ±SD)
MIP (cmH2O) 112.95 ±27.13 †131.09 ±28.20 †116.33 ±40.56 117.00 ±36.40
Blood flow
change rate (%) 19.91 ±11.65 9.63 ±7.62 5.33 ±7.45 13.50 ±7.48
800-m test (sec) 162.97 ±24.96 156.75 ±20.73 166.67 ±21.83 167.60 ±20.73
†
: there is significant difference between pre-training and post-training in IMT groups. * IMT: Inspiratory
Muscle Training.
Medicina 2021,57, 72 6 of 8
Table 3.
The repeated measure two- way ANOVA results of the MIP, blood flow change rate, and 800-m times trial test
between IMT and control group.
Within-Subject (Pre-Post) Between-Subject (Group) Interaction (Group ×Pre-Post)
FpValue
Partial
Eta
Squared
FpValue
Partial
Eta
Squared
FpValue
Partial
Eta
Squared
Power
MIP (cmH2O) 10.966 0.004 * 0.379 0.136 0.717 0.007 9.466 0.007 * 0.345 0.829
Blood flow
change rate (%) 0.272 0.609 0.015 2.443 0.135 0.119 20.691 0.000 * 0.535 0.990
800-m test (s) 3.932 0.063 0.179 0.541 0.471 0.029 7.174 0.015 * 0.285 0.717
*p< 0.05.
4. Discussion
The purpose of this study was to investigate the effects of 4-week inspiratory muscle
training between respiratory muscle strength, limb blood flow change rate and sports
performance in recreational 800-m college runners. Our results indicated that 4-week IMT
significantly increase MIP and improve 800-m run performance and decrease the limb
blood flow change rate. The present study explained and completed the phenomenon
which has seldom been discussed before.
According to our results, the IMT group significantly improved MIP from 112.95
±
27.13 cm
H
2
O to 131.09
±
28.20 cm H
2
O, but the control group did not. One meta-analysis study has
previously pointed out that respiratory muscle training enhances MIP particularly for endurance
exercise [
23
]. The 800-m distance is a sport that includes both aerobic and anaerobic exercise
event [
14
]. Based on our study results, 4-weeks respiratory muscle training enhanced the
sports performance of the 800 m middle-distance running. This result had not appeared in
previous studies.
Previously, a systematic review suggested that 4 to 12 weeks may be a proper duration
for respiratory muscle training [
23
]. In our study, only 4 weeks of IMT with setting intensity
at 50%, 60%, 70% and 80% of MIP, we were able to observe significant improvements. These
results were consistent with previous studies. The previous research group comprised
elite athletes who could quickly learn breathing muscle training skills, so it only needed
50% intensity and 4 weeks of training time to see progress. For the other studies, it took
6–8 weeks for recreational runners. The training effect can be achieved when the intensity
was above 80% [
1
,
15
]. Specifically, a previous study set 50% of MIP as the intensity for
the training group, resulting in significant improvement [
24
]. However, in our study,
the control group was also recreational runners, and set at 50% of the training intensity
for 4 weeks was not enough to see significant results. It was different with previous
studies. It may indicate that recreational runner needs more time and training intensity
to learn breathing training skill. The possible mechanism is not clear. The future study
needs to clarify the effect of training skill on respiratory muscle between recreational and
professional runners.
On the other hand, the limbs’ blood flow significantly decreased from 19.91
±
11.65%
to 9.63
±
7.62% after the IMT training program. Conversely, the control group increased
from 5.33
±
7.45% to 13.50
±
7.48%. It may indicate that consistent intensity does not
improve respiratory muscle function and decrease blood flow change rate in control group.
In general, a maximal exercise may result in vasoconstriction in locomotor muscles [
25
]
and cause peripheral fatigue and, in part due to accompanying high levels of respiratory
muscle working, thereby increases the blood flows [
8
]. Therefore, we found that the control
group at a consistent respiratory muscle training intensity did not affect respiratory muscle
endurance, which in turn affected the amount of blood flow change rate. However, after
the 4 weeks of IMT training, the blood flow changing of the IMT group were reduced.
The possible reason is that the running movement is an upright dynamic pattern on land.
It was required core muscles involved during running, including the diaphragm (both
Medicina 2021,57, 72 7 of 8
respiratory muscles and trunk core muscles) [
17
]. With IMT training, it progresses from
50% to 80% intensity, it can increase the vertical movement of the diaphragm during this
resisted training for respiratory muscles and may promote the perfusion of blood flow to
the limbs, which reduce the influence of metabaroreflex phenomenon. This implies that the
training of incremental IMT intensity attenuated metaboreflex phenomenon and reduced
lower limb blood flow change rate in recreational runners.
The significant improvement in the 800-m running performance from 162.97 ±24.96
sec to 156.75
±
20.73 s was only observed in the IMT group. The same result has been previ-
ously observed. In particular, Nicks and colleagues performed 5-week respiratory muscle
training in soccer players and examined their fitness performance by Yo-Yo Intermittent
Recovery Test. The performance was significantly improved in their study [
26
]. Similar
results have been found in another approach with 4 weeks and 6 weeks of respiratory
muscle training [
27
,
28
]. A meta-analysis has also demonstrated a significant positive effect
of IMT for fitness performances [
23
]. Generally, our results are consistent with previous
research. To conclude, 4-weeks IMT training (twice a day, 5 days a week), progressively
from 50% to 80% of MIP improved 800-m performance in college recreational runners.
The strength of the present study is the participants and sports performance variable
selection. We chose the 800-m timed trial test and 800-m recreational runners. This track
event has belong to both aerobic and anaerobic exercise types. Our results also proved
that the respiratory muscle training is not only effective for endurance exercises, but also
for mixed forms of exercise (both aerobic and anaerobic exercise types). However, some
limitations should be addressed. First, the present study recruited runners with only
one single race in a particular range of age. Future studies are encouraged to investigate
different races, ages, cultures, and types of athletes in order to ensure the cross-validation
of the mechanism. Second, although we have minimized possible interferences in the
study, the consistency of individual factors such as dietary and sleep duration could not be
guaranteed. It may interfere with the results of the research.
5. Conclusions
The present study conducted a 4-week respiratory muscle training intervention in
order to investigate its effects on sports performance for recreational runners. Our results
indicated that the 4-week IMT training (twice a day, 5 days a week) significantly improves
participants’ inspiratory muscle strength, 800-m running performance and decreases the
limb blood flow change rate. A possible mechanism that increasing MIP could delay the
onset of respiratory muscle fatigue and help reduce lower limb blood flow change rate,
finally improved 800-m sport performance.
Author Contributions:
Y.-C.C. (Yun-Chi Chang) critically reviewed the data and drafted the manuscript.
H.-Y.C. and L.-W.C. supervised the study and critically reviewed and modified the manuscript. C.-C.H.,
Y.-C.C. (Yun-Chi Chang), and M.-W.T. participated in the design, conducted the statistical anal-yses,
interpreted the data, and helped to draft the manuscript. P.-F.L. and Y.-C.C. (Yi-Chen Chou) helped to
manage and analyze the data. All authors read and approved the final manuscript.
Funding: This research received no external funding.
Institutional Review Board Statement:
The study was carried out in accordance with the latest
version of the Declaration of Helsinki and was approved by China Medical University & Hospital
Research Ethic Committee (CRREC-102-027, 17 June 2014).
Informed Consent Statement:
Informed consent was obtained from all subjects involved in the study.
Data Availability Statement:
The data that support the findings of this study are available on request
from the corresponding author. The data are not publicly available due to privacy or ethical restrictions.
Conflicts of Interest: The authors declare no conflict of interest.
Medicina 2021,57, 72 8 of 8
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