This study evaluated the effect of inspiratory and expiratory muscle training on pulmonary function, maximal, and sub-maximal exercise performance. Specifically, how does training using a PowerLung resistive device effect exercise performance and pulmonary function in competitive marathoners and triathletes. The participants in this study (N=12) had a mean weekly aerobic training time of 7.5 hours per week of swimming, cycling, or running. Eight subjects were assigned to a PowerLung treatment group and four control subjects were given a sham device that allowed no greater than 15% resistance on inspiration or expiration. The subjects performed 30 maximal inhalation/exhalation maneuvers on their respective devices two times per day for four weeks. The subjects were tested for forced vital capacity (FVC), forced expiratory volume in one second (FEV1), FEV1/FVC ratio, forced inspiratory vital capacity (FIVC), peak inspiratory flow rate (PIFR), and peak expiratory flow rate (PEFR). Each subject was also tested for peak exhalation force test (Pex) as well as a maximal oxygen consumption (VO
The effects of resistance training on skeletal muscle are well documented. When performed with the correct repetition scheme and load assignment, resistance training can produce skeletal muscle hypertrophy, strength, or local muscle endurance. Traditionally, strength and power athletes have used resistance training to augment sport performance while endurance athletes have avoided any type of resistance exercise believing that increased muscle would decrease aerobic performance. However, skeletal muscle controls one of the most important aspects of aerobic conditioning; air movement. The diaphragm, external and internal intercostals, scalene, and abdominal muscles (i.e. respiratory muscles) help to facilitate the increased airflow needed to fuel the increasing needs of oxygen during exercise.3 If these muscles play such a crucial role in exercise, logically one would think we should train them just as if we would any other skeletal muscle.
Devices have been manufactured that offer resistance on inhalation and exhalation and thus cause an increased strain on the respiratory muscles. This resistance has been shown to facilitate positive pulmonary function changes in people with chronic obstructed pulmonary disease (COPD). Villafranca et al.17 showed increases in maximal inspiratory pressure (PImax) after ten weeks of inspiratory muscle training using a threshold inspiratory trainer allowing 30% resistance. Likewise, Larson and Kim7 observed increases in PImax after one month of inspiratory muscle training in people with COPD.
Pulmonary resistance training has also been shown to change enzymatic profiles in sheep. Akabas et al.1 assigned nine adult sheep to a training group and seven to a control group. The experimental group trained for twenty minutes using inspiratory flow resistance (50-100 cmH
Data involving healthy humans using respiratory muscle training, and specifically with exercise is limited. In two separate studies, Suzuki et al.12,13 observed changes in the rate of perceived exertion (RPE) after inspiratory and expiratory muscle training in healthy adults. Suzuki concluded that expiratory muscle training did not decrease RPE at a given work load while inspiratory muscle training did decrease RPE.
Cain and McConnell10 reported increased sub maximal exercise performance after respiratory muscle training. This group found decreases in blood lactate, RPE, and HR along with an increased time to fatigue after four weeks of respiratory training. Boutellier et al.3 reported similar results also after four weeks of respiratory muscle training. Hanel and Secher6 observed a decrease in breaths per minute and an increase in tidal volume after exercising twice a day for 28 days in ten physical education students.
The purpose of our research was to investigate the effects of respiratory muscle training using a Powerlung device on pulmonary function and exercise performance in triathletes and marathon runners. We hypothesize that the treatment group will increase pulmonary function during exercise and increase dynamic lung functions. Furthermore, we believe that the exercising group will increase sub-maximal exercise time as compared to the control group. We do not believe that the treatment group or control group will increase VO
Subjects:
A total of twelve subjects (9 male, 3 female) were recruited from area triathlon and running clubs. The subjects had a mean aerobic training time of 7.5 hours per week (range; 5 – 10 hours). Eight subjects (6 male; 2 female) were assigned to a Powerlung treatment group and four subjects (3 male; 1 female) were assigned to a control group. The experimental group had the following mean physical characteristics: age 36.75 ± 8.83 years, height 174.5 cm ± 9.41, weight 72.94 kg ± 7.22. The control group’s physical characteristics were age 34.5 ± 7.05 years, height 172.8 ± 4.22 cm, and weight 71.23 ± 3.64 kg. Each subject was given an informed consent form and made aware of their right to drop out of the study at any time.
Table 1: Mean±standard deviation (SD) data of group characteristics
Group | N | Age y(rs) | Ht (cm) | Wt (Kg) |
PLT | 8 | 36.75±8.83 | 174.5±9.41 | 72.94±7.22 |
CON | 4 | 34.75±7.05 | 172.8±4.22 | 71.23±3.64 |
Maximal Exercise Testing
Each subject was given a maximal oxygen consumption test (VO
Pulmonary Function Testing
Each subject was given a spirometry test using a ChestTest spirometer (Vaccumed, Ventura, CA) before the VO
Each subject also performed a peak exhalation force (Pex) test to determine the strength of the expiratory muscles. Force was measured using a standing mercury sphygmomanometer. The subject performed a maximal inhalation then exhaled forcefully against a closed valve. Maximal force in mmHg was recorded over a maximum of three trials. The Pex test was performed pre and post training after the spirometry test but before the VO
Sub-maximal Exercise Testing
One to two days after the pre VO
Training:
For the duration of the study, the subjects were asked to maintain their present aerobic training and not to increase or decrease their training time in order to eliminate the possibility of adaptations from aerobic exercise.11 Both groups performed thirty maximal inhalation/exhalation cycles on the Powerlung training device two times per day for four weeks. The device allows for varying resistance on inhalation and exhalation via hand adjusted knobs. After the first sub-maximal test, the treatment group was given the Powerlung device and instructed to perform the above-mentioned protocol as assigned by Powerlung manufacturers. The subjects were instructed to adjust the resistance to allow for the 30th breath on both inhalation and exhalation to be close to a maximal effort (i.e. 30-RM). The subjects controlled the resistance via trial and error.
In the same way, the subjects assigned to the control group were given a sham device after their first sub-maximal test. The sham device looked identical to the Powerlung device, but the chambers inside the sham device were constructed to allow a resistance no greater than 15%. The control subjects were given the same instructions as the experimental group. Neither group was informed as to which group they were assigned to until the completion of their last maximal test.
Statistical Analyses
All data was analyzed using analysis of variance (ANOVA) with repeated measures. The data was copied from a summary spreadsheet in Microsoft Excel to SPSS statistical software and the software derived all F-ratios. All significant F-ratios were analyzed using Tukey’s post hoc test and p-values represent Greenhouse-Geisser adjustment for sphericity. Anthropometric data is expressed as mean±standard deviation (SD), while all exercising and pulmonary dependent variables are expressed as mean±standard error of the mean (SEM). Percent change was calculated using Microsoft Excel with the formula: % change = [(x
Results are provided in Tables 2 and 3 for all maximal exercising and pulmonary function data, respectively.
Table 2: Descriptive statistics (mean±standard error of the mean (SEM)) for data at maximal exercise intensity.
Variable | Pre Mean | Post Mean | % Change | P/ßValue |
PLT VO |
55.35±2.70 | 55.86±2.54 | 0.92% | ß.14 |
CON VO |
53.45±3.95 | 52.53±3.85 | -1.72% | P=0.36 |
PLT V |
138.16±7.37 | 142.71±8.29 | 3.29% | ß.57 |
CON V |
125.60±8.69 | 125.60±9.69 | 0.00% | P=0.04 |
PLT V |
3.03±0.16 | 3.84±0.26 | 26.73% | ß.55 |
CON V |
3.30±0.44 | 3.05±0.45 | -7.58% | P=0.04 |
PLT RRmax (breath/min) | 52.38±2.40 | 50.50±1.60 | -3.59% | ß.84 |
CON RRmax (breath/min) | 47.00±5.48 | 47.25±5.84 | 0.53% | P=0.57 |
PLT VT (%VO |
77.13±7.38 | 74.50±1.54 | -3.41% | ß.13 |
CON VT (%VO |
73.25±5.65 | 75.00±2.35 | 2.39% | P=0.34 |
PLT = Treatment ;
CON = Control ;
VO
V
V
R = Respiratory rate ;
VT = Ventilatory threshold ;
Exercise Variables
The purpose of this study was to determine if pulmonary function or exercise performance could be changed by specifically training the respiratory muscles using a Powerlung resistance device. Respiration is only one component of aerobic capacity. Cardiac output is generally thought to be the major limiting factor to aerobic exercise8. At maximal exercise, the ventilation to perfusion ratio reaches 4.0, indicating that we are ventilating four times the volume of air then is provided to the alveoli by pulmonary blood flow10. Research shows runners with the lower ventilation responses to high exercise are both hypoxemic and more acidotic11. This could be attributed to an inadequate hyperventilation, reducing CO
In a study by Boutellier et al.2 on trained aerobic athletes using a respiratory resistance device different from the Powerlung, the researchers found no significant increases in either VO
Table 3
However, using highly conditioned aerobic athletes did create an ideal situation to control the test the Powerlung. Because our subjects had likely maximized the pulmonary adaptations elicited by aerobic conditioning alone, any changed observed in oxygen consumption or pulmonary function could be attributed to the Powerlung training.
We did expect to see changes in pulmonary function during exercise. Because the subjects had trained their pulmonary muscles, they were able to increase ventilation. The increase in V
Earlier work by Hanel and Secher12 showed similar results. These investigators studied inspiratory muscle training on 20 physical education students. The students trained using a device similar to the Powerlung, but only allowed resistance on inspiration. The students trained on the device for 10 min twice per day at a progressively increasing resistance for 27.5 days. VO
While increased pulmonary muscle function did not result in an increase in VO
Pulmonary Variables
The spirometry readings did not change significantly with Powerlung training. O’Kroy and Coast13 examined nineteen untrained students and randomly assigned them to either a control group, an exercising group, an inspiratory loading group, an expiratory loading group, or a hyperventilating group. The subjects trained four days/week, 20 min/day for four weeks with their assigned groups. The subjects training with inspiratory loading showed increases in MIP and MIF, while the expiratory loading group showed increases in maximal expiratory pressure (M
Tzelpis et al.14,15 showed similar results in a study with nineteen untrained students using flow specific training. Tzelpis assigned the students to three specific groups: a low, medium, and high pressure groups. The high pressure group performed 30 maximal static inspiratory contractions against an occluded valve. The low pressure group performed of thirty maximal inspiratory contractions against an unoccluded valve, and the medium pressure group performed 30 maximal contractions through a 7 mm resistor tube. The results were specific to the type of training. The high pressure training groups had the highest increases in peak esophageal pressure (P
It is known that pulmonary muscles will adapt to aerobic exercise9,10, so we would expect to see smaller changes in aerobic athletes as their pulmonary muscles are already developed. Hanel and Sechler12 showed no change in FEV
Overall, it can be concluded from our research that the Powerlung device does elicit positive changes in the pulmonary muscles. The Powerlung device increased the strength of the respiratory muscles as seen by the increase in P
When doing further research with highly trained athletes, one might also consider trying different training protocols. In all forms of resistance training, not only is the intensity increased, but the overall volume and duration is also varied. Perhaps training at a higher volume (i.e. more reps) might produce more favorable metabolic changes in the respiratory muscles.
As long as athletes and scientist strive to push the limits of human performance every avenue of training will be explored. Pulmonary resistance training with athletes is still relatively new, and has seen only minimal research. As records continue to fall in the athletic world, research should continue on pulmonary resistance training along with all other aspects of exercise performance.
Funding for this study was provided by Powerlung Inc. The authors would like to sincerely thank all participants in this study and the Bay Area Triathlon Club for their advertisement.