Training Intensities - Essay Example

Training Intensities and its Affects on Lung Function in Healthy Individuals Introduction and Background Skeletal muscles control the most important aspects of breathing and air movement. The diaphragm, external and internal intercostals, scalene, and abdominal muscles (i.e. respiratory muscles) help to facilitate the increased airflow needed to meet the increased intake of oxygen in the air during inspiration. The skeletal muscles associated with respiratory muscles consist of types I, IIa, and IIb fibers. Type I fibers are the first to be recruited in the muscle activity during respiration. These fibers produce low levels of force, but are resistant to fatigue. The type IIb fibers are recruited last. They produce high levels of force, but fatigue rapidly. Type IIa fibers are intermediate in respect of the factors of force development and fatigue (Belman, 1993). During exercise these muscles have a critical role to play in maintaining breathing response to the increased physical activity. This makes it logical to assume that these muscles can and should be trained, just as any other skeletal muscle for enhanced physical abilities Amonette, 2001. However, Belman 1993, points out that an appropriate stimulus needs to be applied to achieve training response in these fibers. (Belman, 1993). Inspiratory muscle training has gained a lot of interest over the last decade. Various handheld inspiratory muscle-training (IMT) devices are available in the market and recent evidence suggests that outcomes in inspiratory muscle training vary depending on the IMT program employed. Due to the more active nature of inhalation in the breathing process, most research has focused on the effects of inspiratory muscle training (Weiner et al, 2003). According to Faulkner et al (2001) overload, specificity, and reversibility are the three main principles of designing training regimes to obtain a desired training response. In the case of normal healthy individuals whole body aerobic activity provides a suitable training stimulus for the inspiratory muscles. It is not an ideal training method for COPD patients who may have to lead a more sedentary lifestyle. In addition, patients with spinal injuries may have a weakness of both inspiratory and expiratory muscles, so IMT may be beneficial in sustaining healthy lung capacity while the patient is restricted to movement (Casabury et el 1991). IMT is founded on the basis that as an individual inhales against air resistance, the inspiratory muscles are encouraged to work harder. This training stimulus induces improvements in the force-generating capacity and metabolic efficiency of the inspiratory muscles. The resistance can be adjusted in IMT devices, which enables training to be progressive (Sharpe et al., 1999). Patients with COPD may not able to generate adequate flow for the inhalation of inhaler type medications. This may be the consequence of primary weakness in the inspiratory muscles, which lead to mechanical abnormalities in their chest wall. Studies have demonstrated that inspiratory muscle training improves inspiratory muscle strength (Lisobea et al, 1997; Smith, et al, 1992; Sayer & Clanton 1993, Jong et al, 2001), and endurance (Weiner, et al, 1999; Martinez et al 2001). It has been hypothesized that IMT could be associated with positive changes within the structure of the respiratory muscles, thereby having a potentially positive effect on exercise capacity and improve lung function (Boutellier et al., 1992; Boutellier and Piwko, 1992; Boutellier, 1998; Spengler et al., 1999; Markov et al., 2001; Stuessi et al., 2001). Outcomes of previous studies show variance due to the different training protocols used in these studies. In addition the maximal and optimal intensity a patient can train with using a handheld IMT device to improve inspiratory function is controversial. In some studies it has been found that improvement may occur with as little as 20% of the individual’s maximum inspiratory pressure (MIP), which reflects the maximum strength of the inspiratory muscles (Donner. C. F; Belmen .M. J, 1988). However in other studies the intensities are as high as 80% (Hill. K, et al 2006; Donna K, et al 2007). Bellemaire (1982) suggests that loads greater than 60% of peak force are not sustainable for COPD patients. If this is the case then unnecessary high intensities given to patients could put too much pressure on the inspiratory muscles and affect the treatment outcomes. Rochester (1981) points out that increases in inspiratory muscle strength has been observed in test groups; whish used a sham inspiratory muscle training device with no resistance. (Rochester, D. F 1981). In spite of this overwhelming evidence received from studies that IMT is useful in rehabilitation of those with compromised inspiration capabilities, there are currently no set guidelines available for medical professionals. Journals vary with inappropriate experimental designs and design flaws that have fail to apply the most basic muscle training principles. Purpose The purpose of this study is to test two different training intensities and its affects on lung function in healthy individuals. Literature Review The initial study that targeted training of the respiratory muscles and its effects goes back by three decades, when Leith and Bradley, 1976, tested the effects of training of respiratory muscles in health individuals. They used isocapnic hyperpnoea respiratory training. Isocapnic hyperpnoea resistive training requires continuous monitoring of mixed gas concentrations, which makes it unsuitable for settings outside the laboratory environment. In isocapnic hyperpnoea resistive training a high resistance load is used and the subjects trained for 30 minutes a day. At the end of the five weeks of such training, the strength of their inspiratory and expiratory muscles had increased by an average of approximately 55%. Their vital capacity also increased by an average of four percent over the same period (Leith & Bradley, 1976). Kerns et al (1977) followed this up by reasoning that if respiratory muscle endurance could be improved in healthy individuals then it may be beneficial to train the muscles in people who have respiratory diseases and are more susceptible to muscle fatigue. In 1982, Nickerson and Keens devised a method for measuring ventilatory muscle endurance using sustainable inspiratory pressure (SIP). SIP is the highest pressure a subject can generate in each breath over a time interval of ten minutes. For this purpose they used a weighted plunger as an inspiratory valve. This ensures that a constant pressure is generated with each breath and also allows the subject to vary his tidal volume freely. This method allows for reproducible measurement of ventilatory muscle endurance without dependence on the subject's flow rates or the resistance chosen. This method was used in most studies in the early eighties with different training protocols. It was also used for outcome measures for endurance. Fanta 1983, studied the effect of inspiratory training in healthy individuals. The inspiratory training consisted of a daily routine of twenty maximal inhalations, held each time for ten seconds. The subjects were found to increase their vital capacity by 200ml over six weeks. Maximal inspiratory pressure (MIP) also increased significantly in the training group. Subjects in the control group, who received no training showed no significant change in inhalation measurements. Based on these findings the author concluded that healthy subjects could significantly enlarge their vital capacity and total lung capacity in six weeks, by performing inspiratory muscle exercises. In the Clanton et al 1985, study the focus again was on healthy individuals. Only a small number of subjects of eight were used in this study and there was no control group. The inspiratory muscle training consisted of three sets of inhalation for the duration of two and a half minutes, with an interval of two minutes between each of these sets of exercise. The purpose behind the IMT was to condition the inspiratory muscles to contract with maximum force. The participants were instructed that if symptoms of hyperventilation developed, they were to increase there expiratory time. Complains during this study by the subjects consisted of neck stiffness, popping of ears and chest discomfort. The findings of this study are not reliable, as the study had a very low number of subjects with a very lax protocol Moving on to the 1990s the significant theories on inspiration and inspiration training starts with Pardy and Rochester 1992. In this posit there was a significant positive relationship between the percentage increase in MIP and the training intensity used. According to Hyatt 1996, the peak inspiratory flow (PIF) at a given volume depends on the airway calibers as well as the strength and speed of shortening or contraction of the inspiratory muscles. Many studies use MIP as an outcome measure in there studies. The Smith et al analyses had suggested that most of the studies did not control the intensity throughout the study. This means that if the subject improved after two weeks of training, then the resistance would have to be increased to maintain the same level of training intensity. Recently Golestien et al 2007, has stated that the failure to control for changes in lung volume allows subjects to change their breathing strategy to tolerate a resistive load by altering the lung volume at which it takes place and thereby to reduce the workload to sub training threshold levels. Smith et al 1992, reporting on their findings on IMT based on their literature review of more than one thousand published investigations on IMT, state that the evidence produced at that time hardly supported the belief in benefits of respiratory muscle training in patients suffering from respiratory diseases. However these studies were flawed due to the poor design of the studies and in addition there were variances in the study design, subject selection, assessment tools and training protocols for acceptance of the findings of these studies. . The Tzelepis et al (1994) study tested four groups, all with different training protocols of inspiratory muscle training. The first group performed thirty maximal inspiratory inhalations against a high resistance. The second group performed thirty sets of three maximal inspiratory inhalations with no resistance The third group performed thirty maximal inspiratory efforts on a midrange external resistance and The final group was the control group that did no training. Subsequent to training for five days a week for six weeks, Group 1 increased MIP increased by 37%, but not peak inspiratory flow (PIF). Group 2 increased PIF by 17%, but had no increase in MIP. It was also found that Group three-increased MIP by 17% and PIF by 14%. The control group showed no improvements. It was also found that the greatest increases in respiratory muscle strength occurred with high resistance training, while the highest increases in flow occurred with low resistance training, and intermediate tasks resulted in a uniform increase in strength and flow. Breslin (1997) also agrees that respiratory muscle strength training uses a high load with few repetitions, whereas endurance training necessitates a lower load with more repetitions. In the same year the joint American College of Chest Physicians/American Association of Cardiovascular and Pulmonary rehabilitation committee finally agreed that when a stimulus or load is placed on the respiratory muscles during training, it is sufficient to augment inspiratory muscle strength and there is an associated increase in exercise capacity and a decreased in dyspnoea. Loiters et al (2002) conducted a meta-analyses of IMT studies in the 1990s and found that most studies now controlled the load that participants trained against. Enright (2004) reported that in most studies using IMT for cystic fibrosis the workload was fixed, which gave significant improvements in lung volume and diaphragm thickness ratio. Participants that trained at 80% intensity increased in strength, endurance and lung function. Yet, 20% of the intensity group had an increase in strength and endurance, but no increase in lung function. This is in agreement with Pressure et al (1994) who also found no increase in strength after a 12-week program of IMT at a load equivalent to 22%. This stuffy also found that there was but no increase in lung function. This suggests that intensities of greater than 22% are needed for improvements in pulmonary function (Larson et al 1988, Lisboa et al 1994). However, Joung 2001, in spite of using a training intensity of 40% of MIP over a period of six weeks failed to find improvement in lung capacity, though there was an increase of 17% in endurance. The author ascribes this increase in endurance to the daily frequency of training over the duration of twenty minutes. Sayer and Clanton (1993) found that in 10 weeks of IMT generated significant improvements in MIP. In this study the training protocol required the subjects to breath against training 50-60% load for 30minutes daily. The greater the training intensity and longer duration of intervention may explain the increase in strength. Other studies have demonstrated that high intensity training may not be possible in patients with severe respiratory disease, but there is the possibility for physiological training effects to be achieved at lower intensities (Maltais et al, 1997). Indeed studies have shown benefits at lower training intensities (Clark et al, 1996). Losbia 1994 reports a 34% increase in MIP with a 40% intensity and Villafranca (1998) showed an increases in MIP after ten weeks of training with an intensity of 30%, The findings in increase in MIP at different intensity levels of exercise do not present a clear picture. Huang 2003, found that there was a 36% increases in MIP after 4 weeks, using a 75% intensity with 4 sets of 6 breaths, each set was separated with 1-2 min of quiet breathing. The high intensity low repetitions increased strength significantly. Sturdy (2003) also used a high intensity interval based program, with a 2 minute of IMT then 1min rest for a total of 20 min with a intensity of 68% which gave a 32% increase in MIP. An individual can decrease the breathing frequency by taking bigger and deeper breaths to achieve the same total ventilation volume. Studies suggest that normally the body spontaneously balances the depth of ventilation and the frequency of breathing, so that ventilation is optimally efficient. The time of between each set has to be standardized, so that the training design is consistent. Sturdy (2003) also used a high intensity interval based program, with a 2 minute of IMT then 1min rest for a total of 20 min with a intensity of 68% which gave a 32% increase in MIP. A person can decrease their breathing frequency by taking bigger deeper breaths to achieve the same total ventilation volume. Studies have indicated that normally the body spontaneously balances the depth of ventilation and the frequency of breathing so that ventilation is optimally efficient. The time to rest has been rest between each set has to be standardized so the training is consistent. Beckerman 2005, provided respiratory training to subjects with COPD for 12 months. They used for the first month incremental loading from 15% to 60% and them maintained the training at 60% for the remaining 11 months. They trained 6 days a week, twice daily for 14 min with a threshold trainer. The subjects had an increase in respiratory muscle strength, decrease of dyspnoea, improved quality of life, lower rate of primary care consultation and fewer hospitalisation days. The number of days spent in the hospital by the training group was less than the control group. This was one of the first studies to perform a hospital outcome measure. Magadle 2007, recommends that studies into the effects of respiratory training should include quality of life and dyspnoea outcome measures, as these are the most important outcomes from a patient’s perspective. K Hill et el (2006) reported significant improvements in MIP, endurance, dyspnoea during active daily living and fatigue, with only modest gains in functional exercise capacity. Hill suggests that the improvements may be due to inspiratory threshold loading which has been used previously to study aspects of inspiratory muscle function. Hill used high intensity with a maximal load tolerable for a 2-minute work interval. Compared to previous studies this followed a very strict methodology, which have given them more acceptable and better results than previous studies. Controversy exists over the type of IMT device to be used during respiratory training. A solution to this may lie in the non target inspiratory resistive trainer. In keeping with it name, in the non target inspiratory resistive trainer there is no target to follow. The subject inspires through either a mouthpiece with nose clip or a mask. Attached to either of these devices are a two-way valve and orifices of varying diameters. Resistance is dependent on the size of the orifices. The disadvantage of this is the patient's ability to "cheat" the system by lowering their inspiration workload by simply breathing slower, to lower the inspiratory resistance. At low exercise intensities, a person has more room to varying the rate and depth of each breath. However, as the workload gets high the body assumes much tighter control on breathing and there is far less room for variation in breathing "strategies. Loiters et al (2002) suggests that there are no outcome differences in strength and endurance in the use of many of the IMT devices. Hill (2007) has recently pointed out that when assessing inspiratory muscle function in chronic obstructive pulmonary disease via tests in which the pattern of breathing is unconstrained. The author recommends incremental load tests be used in preference to constant load tests. However, for IMT to be attributed for the changes in these tests to improvements in inspiratory muscle endurance, breathing pattern should be controlled. . Harver (1989) tested his subjects with a target inspiratory resistive trainer. The device generally has a spring-loaded valve, requiring the patient to inspire hard enough to open the valve and permit inspiration against that force. His subjects were instructed to inspire at least 10 times per minute and to adopt a breathing strategy that yielded consistent operation of the feedback mechanism. The findings showed that targeted inspiratory muscle training results in significant increases in respiratory muscle function and significant reduction in dyspnoea. Telesis et al (1994) also used this type of trainer with a high resistance for five weeks, 30 minutes, 5 days a week. The subjects experienced a 36% increase in MIP. The author suggests that the good results found were due to the training device’s visual feedback so that subjects were able to see exactly how much pressure they were generating during training efforts. Abbreviations PIF – peak inspiratory flow (amount of air a person can inhale). MIP – maximum inspiratory pressure (strength of inspiration) Read More