Rowing is a highly demanding sport for both the cardiovascular and respiratory system, and it has been clearly shown that the intensity of the classical 2,000-m rowing race is approximately 100% maximal oxygen consumption (
) (17), which means that each muscle group is highly dependent on the available oxygen. Therefore, rowing training has also been shown to increase the functionality of the respiratory muscles, as shown by maximal minute ventilation rates higher than 200 L·min−1 (22).
One possible way to improve athletic performance is the specific training of the respiratory system, specifically the inspiratory system (15). The inspiratory muscles, including the diaphragm, are morphologically skeletal muscles and therefore, should respond to training under proper physiological load in the same way as any skeletal muscle (12). Inspiratory muscle training (IMT) has been studied before on athletes and nonathletes and its positive effects on performance presented in systematic reviews (9,18), but some controversy remains because the lack of significant effect has also been reported (20). However, less focus has been on using inspiratory muscle warm-up before activity (14,16,27,30). In a previous study Volianitis et al. (28) showed that inspiratory muscle warm-up at 40% of maximal inspiratory mouth pressure (MIP) produced a significant increase of MIP by 8.5%, and they concluded that inspiratory muscle strength can be increased by preliminary warm-up.
Rowers focus on warm-up before each competition to prepare themselves for the upcoming race. It is believed that the whole-body sport-specific warm-up enhances performance and reduces the risk of injury (4). However, taking into account the fact that approximately 70–80% of muscles are used during rowing, it is not the intention of the rowers to perform a very intensive warm-up, as it may result in elevated lactate values at the start of the race. Therefore, the traditional warm-up might not be intensive enough to actually warm-up the inspiratory muscles, thus, the additional respiratory muscle-specific warm-up could be beneficial.
Volianitis et al. (30) compared 3 different warm-up protocols and their effect on maximal rowing performance and dyspnea after a 6-minute all-out test. They found significant increases in rowing performance after a rowing specific warm-up by 3.2%. Furthermore, after adding inspiratory muscle warm-up to the previous rowing specific warm-up, the results improved by further 1.2%. The sensation of dyspnea decreased only in subjects who used inspiratory muscle warm-up. Recently, Wilson et al. (31) indicated that inspiratory muscle warm-up at 40% MIP combined with standard swimming warm-up before the test has a significant effect on 100-m swimming performance in comparison with inspiratory warm-up at intensities of 15% MIP (classified as sham protocol) and 40% MIP only or swimming specific warm-up only.
It can be concluded from the few previous studies that the effect of inspiratory muscle warm-up is relatively small. Therefore, using the maximal all-out tests might not be sensitive enough to detect possible changes in performance as maximal performance is influenced by the motivation of the athlete to produce a maximal result. Furthermore, placebo effect might easily occur when using warm-up with a maximal all-out test. It could be hypothesized that the constant intensity test, where the conditions are more controlled, might be more useful in this case to detect possible physiological changes caused by inspiratory muscle warm-up.
The aim of this study was to investigate the impact of inspiratory muscle warm-up on submaximal rowing performance and to discover if there is an effect on lactic acid accumulation and breathing parameters.
Experimental Approach to the Problem
To assess the effect of the inspiratory muscle warm-up, an investigation with 2 different experimental protocols was planned. At the beginning of the study, spirometry was conducted and the maximal inspiratory mouth pressure (MIP) was assessed. At first, the incremental test was used to measure the individual intensity levels for experimental protocols. After that 2 different rowing, ergometer tests at 90% of maximal aerobic power (Pamax) were performed using either traditional warm-up (test 1) or traditional warm-up in combination with inspiratory muscle warm-up (test 2). The interval between tests 1 and 2 was set to 24–48 hours.
Ten competitive male rowers aged between 19 and 27 years (age, 23.1 ± 3.8 years; height, 188.1 ± 6.3 cm; body mass, 85.6 ± 6.6 kg; rowing experience, 8.5 ± 3.2 years) volunteered to participate in the study and visited the laboratory 3 times. All subjects were either from the national rowing team or the candidates for the team. The experimental protocol was approved by the Research Ethics Committee of the University of Tartu, and all the subjects gave their written informed consent after the procedures of the study had been described. The subjects had to maintain their usual diet during the study period and had to abstain eating 2 hours before tests. Before the first submaximal test, their last meals of the day were recorded and the subjects were asked to consume the identical meal each time before the next test. The subjects were also asked not to participate in any strenuous exercise during the previous 24 hours preceding the test. On test days, no alcohol, coffee, or caffeinated drinks were allowed before the test.
Maximal Inspiratory Pressure and Spirometric Measurement
All subjects underwent spirometry to eliminate abnormal pulmonary function using Spiro 2000 (Medikro OY, Kuopio, Finland). Forced vital capacity, forced expiratory volume in 1 second, peak expiratory flow (PEF), and peak inspiratory flow were measured according to American Thoracic Society and European Respiratory Society (ATS/ERS) guidelines (19). The measured MIP and spirometric values were then compared with the reference data (6,13).
After spirometry, the subjects rested for 15 minutes. Maximal inspiratory pressure, measuring the strength of inspiratory muscles, was then registered according to the present ATS/ERS statement on respiratory muscle testing (19) using MicroRPM (Micro Medical, Kent, United Kingdom). After the maneuver was carefully explained, MIP measurement started from residual volume. To obtain the best value, all subjects had to perform a minimum of 3 and a maximum of 5 attempts with differences not higher than 10%. The average value of 3 acceptable MIP results was used to calculate the load for inspiratory muscle warm-up. All MIP testing was performed with the subject in a seated position.
Incremental Exercise Testing
After spirometry and MIP testing, the subjects rested for 30 minutes. Then, the incremental test protocol was started with a 10-minute individual low-intensity warm-up on a rowing ergometer (Concept II, Morrisville, VT, USA). The resistance of the flywheel was set to number 5 and was kept constant during the test. The first stage was set on 150 W, and the increments were 50 W after every 3 minutes (10). The test was completed if (a) there was a plateau in oxygen consumption, (b) respiratory exchange ratio (RER) increased to a value of 1.1 or more, or (c) the subject could not maintain the given intensity for 5 consecutive strokes. Respiratory variables were measured throughout the test using a breath-by-breath mode, data were stored in 10-second intervals using a portable oxygen analyzer with facemask (Metamax 3B; Cortex GMBH, Leipzig, Germany), and values for oxygen consumption, minute ventilation (L·min−1), and RER were registered. Individual maximal aerobic power (Pamax) during the test was calculated according to the following formula (11):
where P1 = power of the last fully completed stage, P2 = power increment (50 W in our test), and T = duration of the final incomplete stage (in seconds). After finishing the incremental test, the subjects were further familiarized with the IMT device PowerBreathe (IMT Technologies Ltd, Birmingham, United Kingdom) to minimize the learning effect.
Submaximal Intensity Rowing Test at 90% Pamax Intensity
During this investigation, our aim was to avoid the motivational component of the performance test, which could easily be due to placebo effect of the inspiratory muscle warm-up. We have previously used the same test protocol and found that exercising at 95% Pamax intensity resulted in exhaustion within 6 minutes 12 seconds in high-level male rowers (10). Also, Babcock et al. (1) indicated in their study that exercising to exhaustion at 85% of
(8–10 minutes) reduced the inspiratory muscle strength by 15–30%, whereas shorter duration and intermittent work did not bring about the same change. Therefore, we used 90% intensity to avoid volitional exhaustion of the subjects and to perform longer and the intensity of the test should be high enough to indicate the possible effect of inspiratory muscle warm-up. This test was performed twice on the rowing ergometer in randomized design, to exclude the effect of testing order used with regular warm-up only (test 1) or with regular warm-up followed by inspiratory muscle warm-up (test 2). The resistance of the flywheel on the rowing ergometer was set to number 5 and was similar in both tests. During the 90% Pamax test, the subjects had to row as long as they could at the predetermined intensity but not longer than 20 minutes. The display of the rowing ergometer was covered so that the subjects could not see the covered distance or the exercise time. Before test 1, subjects had to perform a standardized warm-up, which consisted of 6 minutes of rowing at 50% Pamax and 2 minutes at 75% Pamax intensity. After that, the facemask and oxygen analyzer were attached and the 90% Pamax test was performed. Before test 2, all subjects had to perform the same standardized rowing warm-up and additionally, a specific inspiratory muscle warm-up with PowerBreathe (2 × 30 inspirations at the intensity of 40% of MIP, with 2 minutes of rest between the sets) (29,31). To maintain the needed level of inspiratory pressure, the PowerBreathe device was connected to the manometer and the subject could see the pressure level on the screen.
During all performance tests, heart rate was monitored with a Polar Sport Tester (Polar, Kempele, Finland) and the respiratory parameters were registered with a portable oxygen analyzer. The duration of the test, distance covered, heart rate, breathing frequency, peak oxygen consumption, RER, and ventilation were measured. When analyzing the data, we excluded the fast component of oxygen consumption and the average respiratory values were calculated during slow component of oxygen consumption. Pre- and postexercise (on third and fifth minute) blood samples were collected from fingertip and analyzed for lactate concentration using the enzymatic method (Lange GMBH, Leipzig, Germany).
The data were analyzed using SPSS for Windows (version 14.0; SPSS, Inc, Chicago, IL, USA). All results were expressed as mean ± SD. The data were checked for normality and the Wilcoxon signed-rank test was used to calculate the changes in parameters over time due to the nonparametric distribution of the data. The statistical significance was set at p ≤ 0.05.
Spirometric and MIP values of the subjects were mostly higher compared with the mean reference values of the healthy population, except the mean PEF value that was comparable with the reference (Table 1).
Table 2 presents the results of the incremental rowing ergometer test, where the maximal oxygen consumption was measured and Pamax was calculated to perform the 2 following experimental rowing tests at the intensity of 90% of Pamax.
Table 3 presents the results of the 2 continuous intensity rowing tests: test 1 and test 2, where the subjects had to perform at 90% Pamax after the standard rowing warm-up and the standard warm-up with the additional inspiratory muscle warm-up, respectively. The only measured parameter that reached statistical significance was breathing frequency (p = 0.039) with no further significant differences between the parameters of the 2 tests. However, there were tendencies (p ≤ 0.1) toward higher ventilation, lower heart rate, and higher RER during test 2 when the inspiratory muscle warm-up was used before the test.
The purpose of this study was to investigate the effect of acute inspiratory muscle warm-up on submaximal rowing performance, lactate concentration, and breathing values. The main finding of the study was that the inspiratory muscle warm-up at 40% of MIP before submaximal rowing does not significantly enhance performance in well-trained male rowers; however, it might have some small effect on physiological parameters. Inspiratory muscle warm-up caused statistically higher breathing frequency.
In our study, we measured the difference between the 2 tests (with or without additional inspiratory muscle warm-up) and did not see any significant difference in time or distance covered during the submaximal rowing ergometer test, performed at the intensity of 90% Pamax. Some authors have found that inspiratory muscle fatigue causes sympathetic blood flow restriction in limb muscles to ensure the work of the respiratory muscles (23,25). One of our hypotheses was that by adding inspiratory muscle warm-up to the standard rowing warm-up, there would be a positive influence on rowing performance due to delaying inspiratory muscle fatigue, and therefore, the blood flow to the limbs would not be affected in the later stage (4,7). Also, the slumped position in rowing might inhibit the ability of the diaphragm to work and lead to earlier fatigue of the inspiratory muscles (5). Therefore, a stronger and more efficient respiratory system might help to maintain the limb blood flow for longer period and enhance the performance of the athlete (32).
In their study, Holm et al. (8) showed that all of their subjects who had higher ventilation after IMT performed better due to the fact that their breathing frequency was higher. They also were able to tolerate increased ventilatory loads without an increase in dyspneic sensation. In this study, we found that breathing frequency was significantly higher (p ≤ 0.05) during test 2, in addition, ventilation indicated a tendency to be higher (p = 0.1) and heart rate to be lower (p = 0.067). Therefore, despite unaltered performance, it seems that an acute bout of inspiratory muscle warm-up might cause some changes in the ventilatory system by altering breathing frequency and might also lower heart rate. If compared with other studies, none of our subjects had a high enough breathing frequency to constitute hyperventilation, a sign of respiratory muscle fatigue (2,26). Therefore, the increase in breathing frequency in our study should not be considered as a negative sign, but more as a possibility to increase ventilation without becoming dyspneic.
The main difference in our study compared with the previously conducted studies is the control of the intensity used during the tests. Although Volianitis et al. (29) used a maximal intensity test, we used the intensity of 90% Pamax (the time of the tests was limited to 20 minutes because changes in the respiratory system should have occurred already by that time). The submaximal intensity was used because the “all-out” or maximal tests rely more on the subjects' motivation and willingness to perform maximally, which could significantly affect the results. Fixed intensity level during the test gives an opportunity to measure the physiological response in constant terms. The negative aspect would be that fixed intensity does not reflect the actual rowing performance that can predict competitive success, and we cannot say whether the inspiratory muscle warm-up has any effect on actual rowing performance (18). However, the mean change of the performance was comparable with other studies (29–31).
There are very few studies that have measured the effect of inspiratory muscle warm-up on blood lactate concentration (16). We hypothesized that inspiratory muscle warm-up might decrease blood lactate concentration after test 2 because of the increased economy of the inspiratory muscles. Previous studies have shown a decrease in blood lactate after IMT and the reason might be a better reusage of lactate by increasing blood flow to the diaphragm and other respiratory muscles (21,24). Another reason for the reduction might be due to the less lactate production of the respiratory muscles performing at the same intensity (3) and also due to “faster” warming-up of the respiratory system at the beginning of the test. In our study, we did not see any changes in lactate concentration between the 2 tests, which could suggest that there is no effect of inspiratory muscle warm-up on submaximal blood lactate concentration during 10–15 minutes of intensity at 90% Pamax. It must also taken into account that the used 90% Pamax intensity might serve as warm-up itself for inspiratory muscles, as the subjects do not start the tests at their maximum effort, which stresses inspiratory muscles at slightly lower individual level. This may result in higher interindividual response depending on the capacity of the respiratory system. Further research is needed to conclude its influence on the results of the current investigation. Nevertheless, the current inspiratory muscle warm-up protocol was not found to have an influence on submaximal performance.
Previous studies have found that inspiratory muscle warm-up with 40% MIP positively affects the performance of rowers during a 6-minute “all-out” test, similar to badminton players and runners performing the Yo-Yo test (16,18,27,29). Similarly, Wilson et al. (31) recently showed a positive effect on 100-m swimming performance using a 40% MIP warm-up, all performances related to high-intensity performance (approximately 100%
). However, Leicht et al. (14) demonstrated that using inspiratory muscle warm-up on active paraplegic individuals did not benefit from the commonly used intensity of 40% MIP. As we also did not see any performance change after inspiratory muscle warm-up during submaximal intensity, the use of different intensities of inspiratory muscle warm-up could be the aim of future studies, for example, to be able to achieve a “faster start” during performances longer than 8–10 minutes.
In summary, we conclude that an acute bout of inspiratory muscle warm-up at 40% MIP before submaximal rowing has no significant influence on respiratory parameters to improve rowing performance despite significantly increased breathing frequency. Further research is needed to better understand the effect of an acute session of inspiratory muscle warm-up and its implications on athletes before competition at different intensities. The possible reasons why we did not see any significant difference in test duration nor distance covered might be the inspiratory muscle load used during the warm-up (40% MIP) and also the choice of submaximal performance intensity on a rowing ergometer (90% Pamax). Further studies should focus on investigating how different inspiratory muscle warm-up intensities and protocols affect the performance of inspiratory muscles, MIP, and athletic performance.
In previous research, IMT has proven a useful method to help perform better in short- and long-term endurance events, but inspiratory muscle warm-up has a less clear relationship. Our study showed that despite causing an increase in breathing frequency and a tendency for higher ventilation, RER, and lower heart rate, the specific inspiratory muscle warm-up protocol used in this study did not increase submaximal performance. Until warm-up protocols with different intensities have been assessed, coaches and athletes should focus more on regular IMT rather than an acute warm-up before the events where the competition is at lower intensity than 100%
The authors are very grateful to the participants who volunteered in this study and to Dr Jaak Talts from the University of Tartu for his technical assistance during the study. This study was supported by the Estonian Ministry of Education and Research grants KKSP 0489 and TKKSP 14058I. The results of this study do not constitute endorsement of the PowerBreathe product by the authors.
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