JBMT Article July 2019: The Pilates Method increases respiratory muscle strength and performance as well as abdominal muscle thickness

The main findings in our study demonstrated an increase in the strength and respiratory muscle performance and in the abdominal wall muscle thickness after eight weeks of PM training in healthy women.

The PM promoted a significant increase in the parameters related to respiratory muscle function, as represented by an increase in MIP, MEP and MVV. The improvement in respiratory muscle strength has been reported in some studies that evaluated the effects of different physical exercise protocols on patients with cystic fibrosis (Dassios et al., 2013), in healthy subjects (Dunham and Harms, 2012) and in athletes (Hackett et al., 2013).

The increase in MIP and MEP may be attributed to a total improvement of the respiratory muscle system, the development of strength in respiratory muscles may be influenced by the mechanical characteristics of the chest and abdominal wall, just as the recruitment of the diaphragm along with other respiratory muscles contribute to stabilizing the trunk and it supplies stimulation for the increase in respiratory muscle strength (Hackett et al., 2013).

Other current reports demonstrated that specific programs for respiratory muscle training also improved the respiratory muscle strength in patients with heart failure (Plentz et al., 2012), quadriplegics (Tamplin and Berlowitz, 2014), and obese (Edwards et al., 2012) and healthy individuals (Enright and Unnithan, 2011). Such data support our findings; however, no previous studies have evaluated the effects of PM on respiratory muscle strength.

During the PM training, the volunteers were constantly stimulated to execute an active respiratory pattern through the abdominal deflation maneuver (MEA), which is the action of “pulling” the abdomen towards the spine. Approximately 200 active respiratory cycles were made in each session, which may explain the improvement in respiratory muscle function, even without using a specific respiratory muscle training method.

There still is a lack of consensus in regards to the amount of effort for obtaining gains in respiratory muscle functions. Dassios et al. (2013)) suggests that a minimum of three forty-five minute workouts per week of moderate to vigorous intensity is adequate do exert beneficiary effects on respiratory muscle strength.

Our results may also be attributed to respiratory re-education via the PM with a direct interference in respiratory muscle action and work (Forgiarini et al., 2007). Our findings are also consistent with a study that adopted Yoga respiratory exercises, also without specific loads to the respiratory muscles, to promote MIP, MEP and MVV in elderly people (Cebrià et al., 2013).

All of the volunteers presented normal lung function with no alterations, except an increase in PEF, in response to the PM. Some studies report that lung function does not change during respiratory muscle training (Tamplin and Berlowitz, 2014) or would occur only with high training loads (80% MIP) (Enright and Unnithan, 2011). This effect was not the aim of our investigation because lung function evaluation was a control variable and we did not hypothesize that alterations would occur in response to the PM training. Up to the present moment there have not been found any reports of an improvement in PEF due to the PM. Given that the PEF results from the expiratory muscle potency, its increase may be secondary to the improvement in respiratory muscle strength and performance as well as muscle thickness.

The present study found an increase on EO, IO and TrA muscle thickness during rest. In similar study (Critchley et al., 2011) identified an increase in TrA thickness after PM training only during the “Hundreds A” exercise, but without alterations in any of the abdominal wall muscles during rest. In such study, the volunteers received verbal instructions from a physiotherapy undergraduate student along, with texts and pictures about the exercises which were then made without individual supervision and executed in training sessions at home in a 45-min programme, twice a week, for eight weeks. Positive results, however, were found in Dorado’s study (Dorado et al., 2012), where after 36 weeks of PM equipment training coached by a licensed instructor with groups of 4 participants, an increase in the rectus abdominis was found along with a reduction of pre-existing asymmetries of the abdominal wall muscles in women; however, this study, similar to ours, also lacks a control group.

Our results demonstrated that the increase in the abdominal wall muscle thickness was greater than that observed in similar studies, perhaps due our protocol that included a higher number of exercises than other studies. Furthermore, the floor exercises were executed following the PM principles and were supervised during the entire time session to ensure correct execution.

The trunk flexion movement in the PM is a common action that uses eccentric and concentric muscle contractions in combination with isometric contractions, thus maintaining a flexed trunk while moving the extremities (Dorado et al., 2012), with a support from the gluteus and lumbar paravertebral muscles, which are responsible for the static and dynamic stabilization of the body (Muscolino and Cipriani, 2004). Eccentric and isometric muscle contractions may provoke substantial muscle hypertrophy and may occur early in a training program (Defreitas et al., 2011), which considering our volunteers’ sedentary condition, may explain the expressive increment in abdominal muscle trophism, as well as in any other report of increased abdominal strength and endurance after strength training in sedentary women (Sekendiz et al., 2010).

Another factor that may considerably interfere with the PM training is the MEA, which is the adequate contraction of the TrA during the exercises that helps to stabilize the spine (Pilates and Miller, 2010). Some reports claim that if the MEA is executed properly, an improvement in the TrA muscle thickness is possible, as much during the execution of the exercises as after the PM and static stabilization programs (Herrington and Davies, 2005, Stevens et al., 2007). The TrA muscle and diaphragm act both over posture control as over breathing, presenting an opposite action on the chest and abdomen as mechanical consequence of this contraction, however, the result of the combined activation of these muscles supplies a mechanism for the central nervous system to coordinate breathing and spine control during the movements (Hodges and Gandevia, 2000).

The proper execution of the MEA was one of the priorities during the PM sessions in our study, which may have carried a fundamental role in the abdominal muscle hypertrophy of our volunteers.

Our results may be justified through adaptations to physical exercise, allowing the generation of alterations in the contractile, morphologic and metabolic properties of the muscle fibers, modifying the length, diameter, strength and type of fiber (Verdijk et al., 2009, Polito et al., 2010). The muscle adaptations occur due to muscle tension stimuli, and they materialized themselves as the activation factor for satellite cells, for these stimuli (tension) induce the liberation of nitric oxide hepatocyte growth factors, signalling the establishment of DNA synthesis and the consequential musculoskeletal tissue (Tatsumi and Allen, 2004).

The presented adaptations may also be tied to a higher recruitment of muscle fibers and motor units (Galvan and Cataneo, 2007) as well as a better synchronism and triggering frequency of these units (Komi, 1986), leading to an increase in strength production.

These physiologic alterations on the skeletal muscle fibers of the abdominal wall may have increased the muscle contraction capacity of the abdomen muscles, facilitating the realization of movements with a greater control and concentration in execution. Therefore, the volunteers were able to coordinate the breathing pattern during each movement.

Our study presented some limitations, such as the absence of a control group and an inability to blind the assessors. The participants presented similar characteristics; however, the application of the intervention protocol and the outcome variable measurements were not conducted by the same researcher. The assessors of the respiratory capacity and ultrasound were experienced, and the data collection techniques were carefully standardized, thus qualifying the study and minimizing errors in evaluating the images and data.

The Mat PM promoted the improvement of respiratory muscle strength and performance as well as the hypertrophy of abdominal wall muscles in healthy sedentary women. These variables have been presented as a therapeutic target in many studies and are related to relevant outcomes, such as functional capacity and life quality. Therefore, this method may promote positive effects on subjects with or without respiratory muscle strength reduction, but should be tested in populations with different chronic diseases.

The set of findings observed in our study may influence the prevention of functional abdominal muscle disabilities and, possibly, minimize the risks of musculoskeletal and ventilatory dysfunction. Furthermore, the use of Mat PM may be used as a potentially useful therapeutic instrument in several populations suffering from respiratory pathologies. Therefore, the effects of Mat PM in special populations, may be recommended in clinical practice.