Abstract
investigated the effects of a functional breathing program on the aerobic performance of recreational runners. Runners participated in an aerobic endurance training program with functional breathing (FBP;n= 8, 34.8±5.1 yrs, 25.3±2.5 kg·m 2 ) or without functional breathing (CON;n= 8, 29±5 yrs, 23±2 kg·m 2 ). The treatment group underwent daily breathing exercises, and nasal-only breathing during low-intensity sessions of the training program. The primary outcome variables measured before and after the program included the following: the breath-hold time at rest, the duration and VO2maxwith nasal- only breathing, and the VO2maxwith normal breathing during a graded running test. The data were analyzed using two-way ANOVA (p< 0.05). We found a significant group x time interaction for breath-hold time (∆from PRE: +1.9 s [CON], +11.7 s [FBP];p= 0.04; d = 1.13). However, the changes in the time and VO2maxwith nasal-only breathing, and in the VO2maxwith normal breathing, did not differ between the FBP and CON groups. A small but significant time (main) effect for the increase in VO2max(~3.0%,p< 0.05) suggested that both groups had adequate stimuli for physiological adaptations. The four- week supplementary functional breathing protocol increased the breath-hold time, but not the maximum
in the time and VO2maxwith nasal-only breathing, and in the VO2maxwith normal breathing, did not differ between the FBP and CON groups. A small but significant time (main) effect for the increase in VO2max(~3.0%,p< 0.05) suggested that both groups had adequate stimuli for physiological adaptations. The four- week supplementary functional breathing protocol increased the breath-hold time, but not the maximum nasal-only breathing time, nasal-only breathing VO2max, or VO2max, in recreational runners. Keywords:functional breathing; breathing exercise; breathing pattern; nasal breathing; aerobic training; VO2max 1. Introduction Nasal-only breathing and hypoventilation breathing exercises, used to induce mild to moderate hypoxia at rest and during physical activity, have become popular in recent years for the purposes of relaxation, wellbeing, and possibly improved physical performance [1,2]. Nasal breathing offers the benefits of filtering, warming, and humidifying air prior to it entering the lungs. However, nasal breathing may also reduce the volume of O2inhaled compared to mouth breathing [3]. Prior literature examining the acute effects of nasal- only breathing on aerobic performance demonstrated that maximal oxygen consumption (VO2max) decreased threefold compared to VO2maxwhen oral breathing was allowed [4]. At VO2max, nasal-only breathing resulted in a lower tidal volume, respiration rate, and fraction of expired oxygen (FeO2), with a concomitant increase in the fraction of expired carbon dioxide (FeCO2) [4]. Despite these acute effects, restricted air intake might serve as a form of hypoventila- tion and inspiratory muscle challenge that provokes a change in chemosensitivity (i.e., a Sports2025,13, 31 https://doi.org/10.3390/sports13020031
Sports2025,13, 31 2 of 10 greater tolerance for CO2accumulation and an increase in pH), with a reduced necessity to accelerate breathing, within the cardiovascular and neurological systems [5–7]. Restrictive breathing techniques for the inspiratory muscles have been shown to improve cardiovascu- lar wellness in older individuals. Inspiratory muscle strength training for 6 weeks reduced blood pressure, improved endothelial function, and reduced reactive oxygen species in adults of 50 to 79 years of age with pre-hypertension [8]. A change in exercise tolerance was not reported in this study. Prior to this, it was demonstrated that inspiratory muscle training in young adults may reduce the metaboreflex, possibly through changing the chemosensitivity of the inspiratory muscles [9]. As the authors of that study and others explain, this adaptation may allow blood flow to be diverted from the inspiratory muscles to the locomotor muscles, and thereby support improved exercise performance [9,10]. The influence of the degree and form of resistance administered on this effect is not clear. Po- tentially, nasal-only breathing during exercise training might impose a similar challenge to effect performance, but this has remained untested up to this point. Nasal-only breathing and functional breathing programs (FBPs) (i.e., breath proto- cols used to optimize the recruitment of the diaphragm or stimulate hypoxia) have been implemented during aerobic training [9,11]. If nasal-only breathing and FBPs limit oxy- gen delivery to working muscles, they might create an acute stimulus for physiological adaptations like those seen with high-intensity interval training [12], but at lower exercise intensities, including exercises completed at rest. Although limited research exists, chronic adaptations of training using nasal-only breathing have included lower ratings of perceived exertion (RPEs) at various running intensities, greater oxygen extraction from the systemic circulation to the working muscles during exercise, and an ability to maintain a similar running velocity at VO2maxcompared to oral breathing, despite reduced ventilation [6,7]. Dallam et al. [6] examined nasal vs. oral breathing during a VO2maxrunning test in partici- pants who had trained (self-selected) for six months using nasal-only breathing at various intensities. The authors found no differences in VO2maxor time to exhaustion between the
exercise, and an ability to maintain a similar running velocity at VO2maxcompared to oral breathing, despite reduced ventilation [6,7]. Dallam et al. [6] examined nasal vs. oral breathing during a VO2maxrunning test in partici- pants who had trained (self-selected) for six months using nasal-only breathing at various intensities. The authors found no differences in VO2maxor time to exhaustion between the nasal-only and oral-only breathing conditions, and no greater increase in blood lactate in the nasal-only condition. Interestingly, nasal-only breathing was able to match the oral-only breathing work levels, with no significant difference in aerobic energy contribution, leading to speculation of an improved running economy and downregulation of the chemoreceptor response to the increased flux of CO2in nasal-only breathing conditions [6]. A popular belief among lay audiences is that hypoventilation breathing exercises at rest may pro- vide increased tolerance for CO2accumulation during exercise [1]; however, this premise currently lacks any scientific evidence. To date, a well-controlled study with pre- and post-treatment testing with a control group has yet to be conducted to determine whether an FBP that utilizes a combination of nasal-only breathing during running and hypoventilation exercises during rest can enhance aerobic capacity in recreational runners. Therefore, the purpose of the present study is twofold: (1) to determine whether a four-week supplemental FBP is effective in improving maximal running time using nasal-only breathing (MNRT) and maximal nasal- only breathing oxygen consumption (MNBVO2) compared to a control group using the same running protocol, but without the FBP; and (2) to determine if there is a relationship between participants’ change in Body Oxygen Level Test (BOLT) time (i.e., breath hold time) and their respective change in MNBVO2(pre- to post-training). We hypothesized that the FBP group would show a significantly larger increase in MNBVO2and MNRT from pre- to post-training, and that the change in BOLT time would show a positive relationship with the change in MNBVO2.
Sports2025,13, 31 3 of 10 2. Materials and Methods 2.1. Participants Participants were recruited from local gyms and running clubs, through word of mouth, and using flyers posted in the community. They were healthy, free of cardiovascular disease, did not take any medication for cardiac issues, and could run at least five kilometers comfortably. Their descriptive statistics are reported in Table written informed consent. The study protocol was approved by the University’s Office of Protection of Research Subjects (Protocol 2019-0303). Table 1.Physical characteristics of participants. Variables Males ( n= 8) Females ( n= 8) Combined ( n= 16) Age (yr) 33.9 ±6.3 29.9 ±5.2 31.9 ±5.9 Height (m) 1.77 ±0.1 1.65 ±0 1.71 ±0.1 Body Mass (kg) 79.18 ±7 61.39 ±7.6 70.28 ±11.5 BMI (kg·m 2 ) 25.3±2.2 22.7 ±2.7 24 ±2.7 Pre-Training VO2max(mL·kg −1 ·min −1 ) 50.5±5.7 44.4 ±6.4 47.5 ±6.6 Values are reported as mean±SD. 2.2. Study Design Using stratification for biological sex, participants were randomly allocated to one of two conditions: running without the FBP (CON) vs. running with the FBP (FBP). The randomization was conducted using the Microsoft Excel randomization feature by placing an equal number of males and females into each group (within cells), then randomly assigning each to either CON or FBP. The participants were individually enrolled and tested, so communication between the control and treatment groups did not occur. Assessments of performance were conducted before and after the four-week treatment period. 2.3. Performance Assessments Participants reported to the lab having completed no strenuous physical activity during the 48 h prior. Their resting heart rate was obtained after the participants had been seated for at least five minutes. The BOLT was performed to identify the duration for which participants could comfortably hold their breath after a normal exhale (an indirect measure of chemosensitivity). Participants took at least three normal breaths prior to a normal exhalation to start the breath hold. The BOLT score was calculated as the time (s) from the beginning of breath hold, when the nose was pinched shut, until the termination of the breath hold, when the nose was released.
breath after a normal exhale (an indirect measure of chemosensitivity). Participants took at least three normal breaths prior to a normal exhalation to start the breath hold. The BOLT score was calculated as the time (s) from the beginning of breath hold, when the nose was pinched shut, until the termination of the breath hold, when the nose was released. Following the BOLT, and after taking height and body mass measurements, participants secured mouth tape (SomniFix International LLC, Chevy Chase, MD, USA) over their closed lips. Participants were then fitted for a facemask (COSMED, Rome, Italy) and heart rate monitor (H10, Polar Electro Inc., Bethpage, NY, USA), and began the treadmill graded exercise test (GXT). Expired gasses were analyzed using a metabolic cart (TrueOne 2400, ParvoMedics, Park City, UT, USA). The GXT used was similar to that used in prior research [13]. Participants began running at 4 mph, at 1% grade, for three minutes. The treadmill speed was then increased to 5 mph for the first stage, and incrementally increased by 1 mph for each subsequent three-minute stage, which allowed for the acquisition of steady-state data on heart rate, ventilation, and RPE during the final minute. The stages progressed until the participants reached a time and speed at which they indicated the need to switch to oral breathing (i.e., MNRT). The test was then paused temporarily as the participants straddled the treadmill. The mouth tape was promptly removed to allow normal breathing and the facemask was
Sports2025,13, 31 4 of 10 repositioned securely. Participants resumed running at the same speed at which the test was paused, and metabolic data collection resumed for completion of the test. Subjects completed the remaining time for the stage in which this pause occurred, and all subsequent stages lasted only two minutes until they reached volitional fatigue. If volitional fatigue was not reached by the end of the fifth stage, the treadmill grade was increased by 2.5% at every stage until volitional fatigue was reached. The main outcome variables included MNBVO2(mL·kg −1 · min −1 ), defined as the greatest 15 s VO2value prior to MNRT (just before the test pause), and VO2max(mL·kg −1 · min −1 ), defined as the greatest 15 s VO2value during the GXT. Running economy (mL·kg −1 · km −1 ) was measured by analyzing the steady-state oxygen consumption for the running speeds during each of the last three stages prior to MNRT (using the average VO2values of the final 15 s of each stage), and was determined by the slope of the line of best fit for the three stages [14,15]. 2.4. Treatment Both groups completed the running program on their own. Compliance was ensured by having participants complete a weekly record that was returned to the researchers after the program. The running program was a polarized design, consisting of two training intensities (i.e., high and low) [16]. Training intensities during the program were set using the heart rate derived at the aerobic threshold (AeT) and estimated ventilatory threshold (VT). The AeT was determined using the Maffetone Formula: 180−Age [17,18], and was used to set the upper limit of low intensity. The VT was determined as the heart rate derived upon visual approximation of where the minute ventilation increased exponentially during the GXT, and was used to set the lower limit of high intensity. Three of the training days were completed at an intensity below the AeT, and a fourth training day was completed above the VT. The total running time per day was matched for both groups. The FBP group supplemented the program with
the minute ventilation increased exponentially during the GXT, and was used to set the lower limit of high intensity. Three of the training days were completed at an intensity below the AeT, and a fourth training day was completed above the VT. The total running time per day was matched for both groups. The FBP group supplemented the program with daily functional breathing exercises, while the CON group did not. FBP participants with BOLT times <30 s were given breathing exercises designed to reduce tidal volume and stimulate a mild hypercapnic response for a short time per session [1]. The mild hypercapnic response (85–94% SpO2) was monitored by participants using a fingertip pulse oximeter (Zacurate Pro Series 500DL FBP, Stafford, TX, USA). Participants with higher BOLT times (≥30 s) were given breathing exercises to stimulate the same effects, but for a longer period per session [1]. These breathing exercises were completed on an individual basis, and were not supervised, due to the high number of sessions that needed to be completed (up to six per day). Participants recorded BOLT times on their compliance sheets every day during the four-week program, and submitted them on day seven of each week. The FBP participants were required to attend a familiarization session, during which they were taught the supplemental functional breathing exercises they would use during the running program. The CON participants were familiarized with the four-week running program after completing the pre-test. Participants were not told which specific “group” they were in, or that groups existed. All they were instructed to do was to complete their exercise program as stated. All participants began their respective four-week programs after completing the pre-treatment graded exercise test (pre-GXT), and reported back to the same lab during the sixth week for their post-treatment GXT (post-GXT). 2.5. Statistical Analysis The descriptive data are presented as the mean±standard deviation (M±SD). Two- way (group x time) repeated-measures ANOVA was used for hypothesis testing of the outcome variables: MNRT (s), MNBVO2(mL·kg −1 · min −1 ), VO2max(mL·kg −1 · min −1 ), run- ning economy (mL·kg −1 · km −1
during the sixth week for their post-treatment GXT (post-GXT). 2.5. Statistical Analysis The descriptive data are presented as the mean±standard deviation (M±SD). Two- way (group x time) repeated-measures ANOVA was used for hypothesis testing of the outcome variables: MNRT (s), MNBVO2(mL·kg −1 · min −1 ), VO2max(mL·kg −1 · min −1 ), run- ning economy (mL·kg −1 · km −1 ), and BOLT (s). Greenhouse–Geisser correction was applied
Sports2025,13, 31 5 of 10 when sphericity of the data was not met. Bonferroni correction for multiple comparisons was used in the case of significant ANOVA interactions. The Pearson correlation coefficient was used to determine the relationship between∆BOLT and∆MNBVO2for the FBP and CON groups, from pre- to post-training. A prioriαwas set top< 0.05. Effect sizes for the differences between the two groups were calculated with Cohen’s d, using the means and standard deviations for the changes in their respective pre- and post-assessment out- comes [19]. The following general accepted categories were applied: small effect, d < 0.2; moderate effect, d = 0.5; large effect d > 0.8 [19]. 3. Results Sixteen participants completed all phases of the study. With the exception of age, no differences existed between the groups in terms of baseline physical characteristics. The mean age for the FBP group was 34.9 + 5.2 y vs. 28.9 + 5.4 y (p= 0.02). For the main outcome variables, no differences existed between the groups at baseline; this suggests that the recruitment and randomization was effective for forming the two cohorts. The average completion rate of the running sessions was 99.3% for the CON group and 96.9% for the FBP group. The average completion rate of the breathing sessions for the FBP group was 91.6%. These data were determined using self-completed compliance sheets that were distributed to participants prior to the program. There were no significant group x time interactions for mean body mass index (BMI), VO2max, MNBVO2, MNRT, or RE (p> 0.05, Table). The effect sizes for the differences between each group pre- and post-change were as follows: BMI, d = 1.1; VO2max, d = 0.11; MNBVO2, d = 0.05; MNRT, d = 0.17; and RE, d = 0.40. Table 2.Pre- and post-treatment group comparisons.Variables CON Pre CON Post FBP Pre FBP Post p-Value BMI (kg·m 2 ) 22.71±2.38 22.82 ±2.56 25.37 ±2.55 24.90 ±2.43 0.075 Body Mass (kg) 68.72 ±13.49 69.11±13.79 71.83 ±10 70.66 ±10.08 0.003 * VO2max(mL·kg −1 ·min −1 ) 46.83±7.1 47.93 ±7.44 48.1 ±6.67 49.52 ±6.36 0.757 MNBVO2(mL·kg −1 ·min −1 ) 37.46±5.34 39.92 ±6.14
Table 2.Pre- and post-treatment group comparisons.Variables CON Pre CON Post FBP Pre FBP Post p-Value BMI (kg·m 2 ) 22.71±2.38 22.82 ±2.56 25.37 ±2.55 24.90 ±2.43 0.075 Body Mass (kg) 68.72 ±13.49 69.11±13.79 71.83 ±10 70.66 ±10.08 0.003 * VO2max(mL·kg −1 ·min −1 ) 46.83±7.1 47.93 ±7.44 48.1 ±6.67 49.52 ±6.36 0.757 MNBVO2(mL·kg −1 ·min −1 ) 37.46±5.34 39.92 ±6.14 37.41 ±3.64 39.63 ±4.44 0.877 MNRT (s) 707 ±191.1 778.25±194.7 782±131.6 828.12±145.2 0.631 RE (mL·kg −1 ·km −1 ) 124.15±38.42 146.66±53.43 121.73±49.23 116.09±26.72 0.273 BOLT (s) 24.38 ±9.6 26.37 ±12.1 22.13 ±8.1 33.88 ±16.0 0.04 * Values are reported as mean±SD. * denotes group x time interaction (p< 0.05). Running economy (RE). A significant group x time interaction was observed for the BOLT time (p= 0.04; d = 1.13) such that the BOLT time increased significantly more for the FBP group compared to the CON group (Figure). There was also an unexpected group x time interaction for body mass (p< 0.01; d = 1.78), with the mean body mass decreasing for the FBP group by approximately 1.1 kg, compared to a slight increase of 0.4 kg in the CON group by the end of the treatment period (Figure). While they were not the primary outcomes being tested, significant main effects were noted for the MNRT (p= 0.038), MNBVO2(p= 0.007), and VO2max(p= 0.028). This would suggest that while the treatment period only lasted only 4 weeks, the program was adequate in duration and intensity to stimulate improvements in participants’ aerobic fitness. The relationship between∆BOLT vs.∆MNBVO2, as seen in Figure, was not statistically significant (r= 0.15,p= 0.570). Likewise,∆BOLT was not statistically correlated with ∆VO2maxor∆RE.
Sports2025,13, 31 6 of 10Sports 2025, 13, x FOR PEER REVIEW 6 of 10 BOLT (s) 24.38 ± 9.6 26.37 ± 12.1 22.13 ± 8.1 33.88 ± 16.0 0.04 * Values are reported as mean ± SD. * denotes group x time interaction (p < 0.05). Running economy (RE). Figure 1. The difference in mean BOLT times between the groups, before and after treatment. There was a significant interaction, such that mean BOLT scores increased for FBP group compared to CON group (p < 0.05). * denotes this significant interaction. Figure 2. The mean body mass for the groups before and after treatment. An interaction was ob- served (p < 0.01), such that the FBP group lost weight on average, while the CON group gained weight. * denotes this significant interaction. Figure 1.The difference in mean BOLT times between the groups, before and after treatment. There was a significant interaction, such that mean BOLT scores increased for FBP group compared to CON group (p< 0.05). * denotes this significant interaction.Sports 2025, 13, x FOR PEER REVIEW 6 of 10 BOLT (s) 24.38 ± 9.6 26.37 ± 12.1 22.13 ± 8.1 33.88 ± 16.0 0.04 * Values are reported as mean ± SD. * denotes group x time interaction (p < 0.05). Running economy (RE). Figure 1. The difference in mean BOLT times between the groups, before and after treatment. There was a significant interaction, such that mean BOLT scores increased for FBP group compared to CON group (p < 0.05). * denotes this significant interaction. Figure 2. The mean body mass for the groups before and after treatment. An interaction was ob- served (p < 0.01), such that the FBP group lost weight on average, while the CON group gained weight. * denotes this significant interaction. Figure 2.The mean body mass for the groups before and after treatment. An interaction was observed (p< 0.01), such that the FBP group lost weight on average, while the CON group gained weight. * denotes this significant interaction.Sports 2025, 13, x FOR PEER REVIEW 7 of 10 Figure 3. Scatterplot of pre- and post-change
Description
This study examines the impact of a breathwork protocol on runners' aerobic performance.