Keywords
Sedentary behavior; Muscle thickness; Diaphragm; Physical activity; Ultrasonography
This article is included in the Manipal Academy of Higher Education gateway.
Sedentary behavior; Muscle thickness; Diaphragm; Physical activity; Ultrasonography
We have corrected the article based on reviewers’ suggestions with slight modifications in the methodology, a revised figure 1, and general minor changes throughout the manuscript.
See the authors' detailed response to the review by Małgorzata Pałac
See the authors' detailed response to the review by Ranganath Gangavelli
Physical activity (PA) (any bodily movement produced by skeletal muscles that require energy expenditure) is crucial for potential health benefits and protection against chronic diseases.1 Insufficient physical activity and sedentary behavior (SB) (any waking behavior characterized by an energy expenditure of 1.5 metabolic equivalents (METS) or less while sitting or reclining) are now associated with an increased risk of cardiometabolic disease and cancer.2 Experimental studies have administered several interventions to address the increasing burden of physical inactivity and SB. However, observational studies have established a relationship between PA and SB, with the health risks remaining still unclear, as there could be health risks associated with SB.3
Muscle mass and strength are predictors of performance enhancement and ability to work in adults and mobility functions in the elderly population.4 Furthermore, peripheral muscle mass and strength are associated with chronic diseases like sarcopenia which is a major risk and early mortality. Though anecdotal evidence claims a bidirectional relationship between physical inactivity and peripheral muscle strength or thickness, observational studies establishing the relationship are lacking. In young, healthy people, there is a substantial correlation between overall muscular strength and higher-intensity PA, and age-related reductions in muscle size and strength have been seen to coincide with lower activity levels.5–7 According to our knowledge,3 a person’s level of moderate to vigorous physical activity (MVPA) is associated with broader benefits including improved cardiorespiratory fitness and total work capacity, but not directly to muscle growth and strength.5,8 The evidence regarding the relationship between levels of PA and the peripheral muscle (soleus, gastrocnemius, and diaphragm) is still debatable using an ultrasonogram.
We hypothesized that: 1) there is a possible change in the muscle thickness and strength of individuals engaged in some PA compared to a sedentary lifestyle, and 2) a change in the thickness of muscles changes as age progresses.9 Hence we aimed to relate various dimensions of PA and sitting time with the diaphragm & lower limb muscle thickness.
This study was a prospective single-centered randomized crossover trial conducted between January 2022 to November 2022 in the Department of Radio-diagnosis and Imaging, Kasturba medical hospital, Manipal, India. Institutional Ethics Committee, KH (IEC2: 125/2022) and Clinical Trial Registry of India (CTRI/2022/10/046187) https://ctri.nic.in/Clinicaltrials/rmaindet.php?trialid=72850&EncHid=34225.86311&modid=1&compid=19 approved the study. Figure 1 depicts this methodology.
We recruited the potential participants from the patients who were waiting for the radiological screening from the radiological department of the multidisciplinary teaching hospital. The written consent was obtained from the participants, also they were asked about their basic details which included history of smoking and alcohol consumption. The participants were first screened for the exclusion factors like recent trauma, orthopedic interventions, bed-ridden, paralyzed, osteoarthritis, and other chronic diseases of the heart and lungs which can hamper the diaphragm thickness. Hence, we included both male and female patients aged 18 – 35 old for the following study.
Self-reported PA was assessed using Short International Physical Activity Questionnaire (S-IPAQ) for young and middle-aged adults. The questionnaire evaluates the amount of time (frequency and duration) spent engaging in activities of vigorous, moderate intensity, walking, and sitting over the course of the previous seven days. The vigorous, moderate, and walking intensities were quantified as 8, 4, and 3.3 metabolic equivalents (METS).
Sample size calculation
We required 91 samples to achieve a moderate correlation (r1 > 0.4) at an alpha level of 95% and an 80% strength. The algorithm for determining the cumulative correlation coefficient distribution is used in all analyses.10
The lower limb muscles measured in this study were the soleus and quadricep muscle (rectus femoris and vastus intermedialis) in both limbs. For measuring the diaphragm, the patient was laid supine and measured at both inhalation and exhalation using the M Mode ultrasonography. The measurement pattern is depicted in Figure 2.
We used the ultrasound machine with linear and curvilinear transducers for the following study. All patients were screened for their anterior quadriceps, soleus, and diaphragm measurements.
The anterior thigh muscle of all subjects will be measured using a 13MHz linear array probe. The B-model ultrasound was used to identify the anterior quadriceps muscle. The patient will be placed in a supine posture with their knees extended and their feet in a neutral position. The distance that lies between the anterior fascia of the rectus femoris muscle (RF) and the posterior fascia of the vastus intermedius muscle will be evaluated to calculate the anterior thigh muscle thickness (TMT). An axial cross-sectional image of the anterior quadricep muscle is obtained of both limbs and recorded.11
An ultrasound with a 13 MHz linear probe was used on distal 1/3 of the calf length which was used to obtain soleus muscle imaging. The B-model ultrasound was used to identify the soleus muscle. Participants were oriented in a prone position, knees outstretched and 0° dorsiflexion of the ankle or knees bent at 30° in the prone position with a pillow underneath. To keep track of muscle movement, the ultrasound device was switched to M-mode to trace motion.12
The chest wall was aligned perpendicularly with a 13-MHz linear array transducer. Using M-mode, the diaphragmatic thickness was determined. Tdi, ee (Diaphragmatic thickness at end-expiration) and Tdi, pi (peak inspiration) measurements were already taken on consecutive breaths, which were seen in a single M-mode image. The diaphragmatic thickness was determined as the distance between the diaphragmatic pleura and the peritoneum. The thickness of the diaphragm for each experiment has been recorded as one value was taken on inhalation and exhalation.13,14
The study included 91 patients aged 18 to 35 with N = 78 male subjects with mean age and standard deviation of 27 ± 4.67 and N = 13 females with mean age and standard deviation of 28 ± 4.67.
In responses to inquiries on lifestyle factors including drinking and smoking, it was discovered that 30 of the 91 patients smoked frequently and 6 had drinking habits. The following data is shown in Table 1.
The participants were divided into three distinct categories: low (n = 6), intermediate (n = 46), and high METS score (n = 39, 42.85%). The results showed that the low METS score was 500.66 minutes per week, the moderate METS score was 1969.69 minutes per week, and the high METS score was 4408.17 minutes per week.
Based on the PA and IPAQ scores, we divided patients into low, moderate, and high PA. When we compared the muscle thickness with the PA, we found the following results. The left and right quadriceps values (rectus femoris and vastus intermedialis) were significantly increased as PA increased.
We found that the association between PA and muscle thickness was significant in the lower limb muscles, with a p-value lower than 0.01. The diaphragm thickness showed a positive association with PA but was not statistically significant, as the p-value were 0.35 for inhalation and 0.17 for exhalation. The data are presented in Table 2. The Pearson correlation results for lower limb muscle thickness with the PA levels are depicted in Figure 3. All the graphs depict a positive correlation between muscle thickness and PA (Figure 3).
Desk-based workers mostly lead a sedentary lifestyle hence their PA level was comparatively lower than those who had an active lifestyle.15 In the majority of the studies, unemployment is detrimental to health behavior.15 Furthermore, it is believed that both the physical and social environments play an important role. In addition, Owen et al. reported that adult participation in PA was influenced by a range of personal, social, and environmental factors and those individual-level variables such as socioeconomic status and perceived self-efficacy demonstrated the strongest association with PA behavior (sitting time, workout time).15,16
Our study aimed to look for the possible relationship between muscle thickness and various levels of PA. According to our research concept, the research was focused on a few factors, including age, appropriate muscles for this investigation, and potential repercussions.17
A total of 91 patients were included in our study, of which six were sorted into the LPA, N = 46 for moderate PA, and N = 39 for VPA; these make about 7% of the participants perform LPA, 50% with moderate PA, and 43% with VPA. Previous studies that have considered a larger population in India have found that around 54% of the total sample they had were physically inactive, and 14% had high PA.18 Internationally, around 15.8% of the people in East and Southeast Asia are physically inactive.19
In our study, we observed that the soleus muscle thickness was 1 cm in LPA and 2.2 cm in VPA (p = 0.001), while the quadriceps muscle thickness (rectus femoris and vastus intermedialis) was 1.3 cm in LPA and 2.8 cm in VPA. The diaphragm thickness was 0.19 cm in LPA and 0.29 (p = 0.358) in PA. A study by Schoenfeld observed the difference in the muscle thickness for low versus high resistance exercises and found that the high resistance exercises were improving the quadriceps muscle thickness by 9.5%.20 This supports our results that show that increased PA improves muscle thickness.
The study conducted by Silva et al. in 2010 observed that Asians have lower skeletal muscle mass as compared to African Americans, Whites, and Hispanics.21 The muscle thickness that we measured in our study without considering the PA level was 1.78 cm and 1.79 cm for the right and left quadriceps (rectus femoris and vastus intermedialis) respectively, and 1.55 cm and 1.56 cm for the right and left soleus muscles respectively.
The reason for selecting the quadriceps, soleus in the lower limb, and the diaphragm for the study were that many researchers have found that there is a change in muscle thickness as age progresses, and it differs with sex as well.22 In 2010 Katsuo Fujiwara et al. reported that compared to their contemporaries in their 20s, men and women who were at least 60 years old had significantly thinner gastrocnemius muscles. With regards to the soleus, neither sex’s age group showed any appreciable changes in soleus thickness. For the gastrocnemius but not the soleus, muscle thickness decreased more from age 40 to 79. These findings support the idea that the gastrocnemius deteriorates and atrophies more rapidly than the soleus. One of the variables that contribute to a decline in muscle strength is aging. Age generally results in a loss of muscle mass and strength.9 According to previous studies, men’s skeletal muscle degradation is correlated with age at about 27 years of age.13 With this clause, we have restricted our study age group to between 18–35 years. The diaphragm muscle thickness showed much less changes during inhalation and exhalation, which showed a negative association between inhalation and exhalation values. Enright et al. discovered that In healthy people, the dimensions of the diaphragm can be increased by weight training. The effect of inspiratory muscle training (IMT) on diaphragm thickness has not been previously reported in healthy people.23 In Enright et al.’s study the group demonstrated an increase in diaphragm thickness. The rise in diaphragm thickness might lead to improved pulmonary mechanics, enhanced inspiratory muscle efficiency, or even both.
In this study, we focused on the lower limb muscles and diaphragm to get a prospective idea of the relationship of these muscles with PA. When humans are physically active, the lower body is most engaged in these activities. PA could be as simple as walking or running. Most likely, the lower body muscles are active while the breathing pattern changes simultaneously, therefore the diaphragm is engaged too. Recent research has shown that diaphragm thickness changes with increased PA, such as weight training.23 In addition, quadriceps, soleus, and gastrocnemius muscles show the greatest activation during the quiet standing posture. These muscles are also vigorously activated in the stance phase of walking to maintain the standing posture and generate forces for propulsion.
With all these factors as constants and variables, our study shows that positive correlation with physical activity levels, there is a significant increase in the quadriceps (rectus femoris and vastus intermedialis), soleus muscle and diaphragm thicknesses, with mean values of 1.3 cm, 1.78 cm and 2.8 cm in LPA, moderate PA and VPA respectively for the quadriceps muscle (rectus femoris and vastus intermedialis); 1 cm, 1.56 cm and 2.2 cm for soleus, and 0.19 mm, 0.25 mm and 0.29 mm for the diaphragm, with increasing PA levels from LPA to moderate PA to VPA respectively. The changes in the lower limbs showed statistically significant results.
Peripheral muscle thickness has been found to positively correlate with physical activity levels. However future trials should further expand the association with the objectively measured PA levels.
Due to the fact that the PA measures utilized in the study were self-reported, there is a risk of recalling bias and response bias. Instead of employing a self-reported questionnaire, future studies could use objectively assessed PA.
Using IPAQ, which provides subjective measurement, we were able to determine the patients’ PA parameters in the current study. Due to observational studies’ use of self-perceived PA, which is frequently unjustified, our comprehension of the association between PA and muscle thickness currently is still unclear. This calls for additional studies employing objectively measured PA.
The nature of the cross-sectional approach used in the research made it difficult to determine the actual link between PA and changes in muscle thickness. If one adopts this approach, one might have a better grasp of how lifestyle factors affect individual muscle strength. Future research should look into these lifestyle choices and take them into account since they can have an impact on these results. Understanding how PA and lifestyle choices affect muscular strength requires studies that demonstrate associations between changes in muscle thickness and PA.
Harvard Dataverse: Active adults have thicker peripheral muscles and diaphragm: a cross-sectional study, https://doi.org/10.7910/DVN/MVFLMY.
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Is the work clearly and accurately presented and does it cite the current literature?
Yes
Is the study design appropriate and is the work technically sound?
Yes
Are sufficient details of methods and analysis provided to allow replication by others?
Yes
If applicable, is the statistical analysis and its interpretation appropriate?
I cannot comment. A qualified statistician is required.
Are all the source data underlying the results available to ensure full reproducibility?
Yes
Are the conclusions drawn adequately supported by the results?
Yes
Competing Interests: No competing interests were disclosed.
Reviewer Expertise: Back pain and motor control exercises, Neural correlates and executive functions, manual therapy
Is the work clearly and accurately presented and does it cite the current literature?
No
Is the study design appropriate and is the work technically sound?
Partly
Are sufficient details of methods and analysis provided to allow replication by others?
No
If applicable, is the statistical analysis and its interpretation appropriate?
No
Are all the source data underlying the results available to ensure full reproducibility?
Yes
Are the conclusions drawn adequately supported by the results?
Yes
Competing Interests: No competing interests were disclosed.
Reviewer Expertise: Muscle morphology, physical performance, healthy ageing, strength and conditioning.
Is the work clearly and accurately presented and does it cite the current literature?
Partly
Is the study design appropriate and is the work technically sound?
Partly
Are sufficient details of methods and analysis provided to allow replication by others?
Partly
If applicable, is the statistical analysis and its interpretation appropriate?
Partly
Are all the source data underlying the results available to ensure full reproducibility?
Yes
Are the conclusions drawn adequately supported by the results?
Partly
Competing Interests: No competing interests were disclosed.
Is the work clearly and accurately presented and does it cite the current literature?
Partly
Is the study design appropriate and is the work technically sound?
Partly
Are sufficient details of methods and analysis provided to allow replication by others?
Partly
If applicable, is the statistical analysis and its interpretation appropriate?
Partly
Are all the source data underlying the results available to ensure full reproducibility?
Partly
Are the conclusions drawn adequately supported by the results?
Partly
Competing Interests: No competing interests were disclosed.
Reviewer Expertise: Respiratory muscle ultrasonography, Physiotherapy, Shear wave elastography
Is the work clearly and accurately presented and does it cite the current literature?
Partly
Is the study design appropriate and is the work technically sound?
Partly
Are sufficient details of methods and analysis provided to allow replication by others?
Yes
If applicable, is the statistical analysis and its interpretation appropriate?
Partly
Are all the source data underlying the results available to ensure full reproducibility?
Partly
Are the conclusions drawn adequately supported by the results?
Partly
References
1. Dhungana A, Khilnani G, Hadda V, Guleria R: Reproducibility of diaphragm thickness measurements by ultrasonography in patients on mechanical ventilation.World J Crit Care Med. 2017; 6 (4): 185-189 PubMed Abstract | Publisher Full TextCompeting Interests: No competing interests were disclosed.
Reviewer Expertise: Musculoskeletal Health, Mobilization, Pain.
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