Exercise May Increase Oxidative Stress in the Sciatic Nerve in Streptozotocin-Induced Diabetic Rats.

Background and Objectives: Diabetic peripheral neuropathy (DPN) affects approximately half of patients with diabetes mellitus (DM), contributing to falls and fractures. Oxidative stress, which is linked to DM-induced hyperglycemia, has been implicated in the onset of DPN. Although exercise is recommended for patients with DM, its effect on DPN remains unclear. Therefore, this study aimed to investigate the effect of exercise on DPN and the mechanisms involved. Material and Methods: Thirty male Wistar rats were divided into control, streptozotocin (STZ)-induced diabetic (DM), and STZ-induced diabetic/exercise (DM + Ex) groups. Diabetes was induced using STZ injection. Rats in the DM + Ex groups underwent six weeks of treadmill exercise. Sciatic nerve parameters, which included motor nerve conduction velocity (MNCV), antioxidant enzymes (catalase, glutathione peroxidase [GPx], and superoxide dismutase [SOD]), oxidative stress markers (malondialdehyde [MDA] and 4-hydroxy-2-nonenal [4HNE]), and neurotrophic factors (brain-derived neurotrophic factor [BDNF] and nerve growth factor [NGF]), were examined. Results: Exercise alleviated DM-induced decreases in MNCV in rats. Although exercise did not significantly affect antioxidant enzyme activity, 4HNE levels increased significantly, indicating increased oxidative stress. Additionally, exercise did not significantly affect DM-induced increases in NGF and BDNF levels in rats. Conclusions: Exercise may prevent DPN in rats with DM, possibly through nonantioxidant mechanisms.

Antiproliferative and anti-inflammatory effects of fractionated crude lectins from boiled kidney beans (Phaseolus vulgaris).

In this study, we investigated the biological profile of lectins isolated from raw and boiled Japanese red Kintoki beans (red kidney beans [RKB]; Phaseolus vulgaris). Lectins in beans showing agglutination activity were retained after heating. Raw and boiled RKB lectins were fractionated using carboxymethyl- and diethylaminoethyl-Sepharose, respectively. Boiled RKB lectins were evaluated for carbohydrate specificity as well as cytokine-inducing and antiproliferative activities against cancer cells and compared with raw RKB lectins. Raw RKB lectins showed specificity for thyroglobulin and fetuin, whereas boiled lectins showed specificity for N-acetylneuraminic acid. Raw RKB lectins showed low resistance to proteases and tolerated temperatures greater than 80°C for 5 min. Notably, lectins from raw and boiled beans showed antiproliferative activity against five types of cancer cells B16, LM8, HeLa, HepG2, and Colo 679. In particular, lectins from raw beans exhibited a significantly stronger activity than those from boiled beans. Anti-inflammatory effects were notably observed in crude extracts from raw and boiled beans. Specifically, lectins fractionated from boiled beans markedly inhibited the expression of tumor necrosis factor-α and interleukin-6. Overall, our results showed that RKB lectins from boiled beans exert anti-inflammatory and anticancer effects and could be developed as potential chemopreventive agents. PRACTICAL APPLICATION: Japanese red kidney beans (RKB) are cultivated in numerous parts of the temperate zone and consumed in many countries. Lectins from boiled beans exhibited anticancer activity, similar to lectins from raw beans. Additionally, crude and fractionated lectins from boiled beans showed anti-inflammatory activity. Thus, boiled RKB lectins have the potential to be used as a bioactive protein for medical research and could be developed as anticancer agents.

Comparison of Physical Function among Elderly Japanese Women with and without Low Bone Mass and Low Muscle Mass: A Cross-Sectional Study of Older Women Who Engage in Regular Physical Activity.

A decline in physical function is common among elderly people who have lost both bone and muscle mass. The aim of this study was to investigate the relationship between low bone and muscle mass and physical function in elderly women of different age groups who exercise regularly. The analysis included 299 elderly women. Low bone mass was determined by a T-score of −2.5 or less, and low muscle mass was determined by a skeletal muscle mass index of <5.7 kg/m2. Physical function was measured by grip strength, knee extension strength, standing ability, gait function, and balance function. The participants were divided into four groups based on bone and muscle mass (healthy, low bone mass, low muscle mass, and low bone and muscle mass groups), and their physical functions were compared. There were no statistically significant differences in physical function between the low bone and muscle mass and the healthy groups. There were also no statistically significant differences in physical function among the four groups in the late elderly stage (75 and older). Elderly women who exercise regularly are less likely to experience a decline in physical function, even if they have reduced bone and muscle mass.

Relationship Between Age-Related Changes in Skeletal Muscle Mass and Physical Function: A Cross-Sectional Study of an Elderly Japanese Population.

Skeletal muscle mass and muscle strength are positively correlated, but the relationship between grip strength and global muscle strength is controversial. This study aimed to clarify the changes in site-specific skeletal muscle mass by age group and determine the relationship between site-specific, age-related changes in skeletal muscle mass and physical function in community-dwelling elderly people in Japan. The participants were divided into age groups of five-year intervals (65-69 years, 70-74 years, 75-79 years, and ≥80 years) and were also categorized by sex. The skeletal muscle mass of the upper limbs, lower limbs, and trunk was measured using multifrequency bioelectrical impedance analyzers (InBody 430 (Biospace Co., Ltd., Seoul, Korea) and InBody 470 (InBody Japan Inc., Tokyo, Japan)). For physical function assessment, we measured grip strength, quadriceps strength, sit-up count, sit-and-reach distance, and standing time on one leg with eyes open and performed the timed up and go (TUG) test. The results showed that skeletal muscle mass decreased with age regardless of sex at all measured sites. Furthermore, a partial correlation analysis adjusted for age, physical constitution, and the presence/absence of exercise habits revealed that the highest correlation was between skeletal muscle mass in all sites and grip strength. Thus, monitoring grip strength may be used as a representative of systemic skeletal mass even in Japanese people.

Factors Influencing the Development of Mild Cognitive Impairment in Community-Dwelling People Aged 75 Years and Older.

In Asia, including Japan, dementia incidence peaks in older adults over ≥75 years; it is therefore important to detect mild cognitive impairment (MCI), and prevent its onset in this age group. Our study hypothesized that physical and psychological status would be associated with MCI incidence among community-dwelling people aged 75 years and older. The study population comprised 291 such individuals. Participants with a Mini-Mental State Examination score of 28 or more were considered non-MCI, and those with a score of less than 28 and greater than 24 were considered to have MCI. Several other measures were also evaluated, including information about their current medical visits due to diseases, depressive symptom severity, various physical functions (trunk function, 30 s chair-stand test, one-legged stance test, timed up and go test time, 5 m walking time, grip strength, knee-extension strength, and toe-grip strength), and body composition (body fat and skeletal muscle mass). Participants suspected of having MCI had significantly shorter educational histories, higher rates of medical visits due to hypertension, and poorer balance abilities. The results suggest that these indices can be considered screening indicators for detecting MCI in people aged 75 years and older, which may be useful for planning intervention programs for this population.

Physical performance in relation to preserved ratio impaired spirometry: a cross-sectional study of community-dwelling older Japanese adults.

Preserved ratio impaired spirometry (PRISm) is associated with an increased mortality rate; however, its characteristics have not been clearly identified in Japan. This cross-sectional study of community-dwelling older adults compared physical function between people with PRISm and those with no respiratory issues, from 2014 to 2019. We collected demographic data through interviews and measured respiratory and physical functions. We included 668 older adults (male, 23.5%; mean age, 72.8 ± 5.6 years); the prevalence of PRISm was 12%, while the prevalence of obstruction was 6.9%. Propensity score matching was used to identify control subjects with normal spirometry (n = 80) while minimizing the effects of confounders during comparisons with the PRISm population (n = 80). Compared with community-dwelling older adults with normal lung capacity, older adults with PRISm had a lower forced vital capacity (%FVC; 68.7 ± 9.1% vs. 92.5 ± 12.7%, p < 0.001), lower core muscle endurance (sit-up test: 6.7 ± 5.8 vs. 8.7 ± 6.0, p = 0.032), and a longer one-leg stance duration (52.4 ± 41.1 s vs. 36.4 ± 34.1 s, p = 0.008). In multivariable logistic regression, %FVC and increased one-leg stance were independent predictors of PRISm status. The prevalence of PRISm among community-dwelling elderly Japanese exceeds that of obstructive lung disease and is associated with reduced %FVC and better performance on balance testing.

The Relationship between Subjective Cognitive Decline and Health Literacy in Healthy Community-Dwelling Older Adults.

Few studies have examined the effects of health literacy on people at risk of developing dementia; its effects on the pathogenesis of subjective cognitive decline (SCD) are particularly unclear. This study aimed to clarify the relationship between health literacy and SCD in a population of healthy community-dwelling older adults. SCD status was assessed using the Cognitive Function domain of the Kihon Checklist (KCL-CF). Health literacy, in turn, was evaluated using the Communicative and Critical Health Literacy (CCHL) scale. Global cognitive function and depressive symptoms were evaluated using the Mini-Mental State Examination (MMSE) and a five-item version of the Geriatric Depression Scale (GDS-5), respectively. Participants who were suspected of having SCD were significantly older than their non-SCD peers, and scored significantly worse on the CCHL, MMSE, and GDS-5. In addition, SCD status was found to be associated with CCHL and GDS-5 scores, as well as age, according to a logistic regression analysis. These findings suggest that low health literacy is linked to SCD morbidity in healthy community-dwelling older adults and should prove useful in the planning of dementia prevention and intervention programs for this population.

The Association between Health Literacy and Gait Speed in Community-Dwelling Older Adults.

The association between gait speed, a vital health outcome in older adults, and health literacy, an important health promotion aspect, is unclear. This study examined the relationship of gait speed with health literacy, physical function, and cognitive function in community-dwelling older adults. The subjects were 240 older adults (52 men, mean age 73.8 ± 6.0 years). Gender, age, and education were self-reported, while height and weight were measured directly. Health literacy was evaluated using Communicative and Critical Health Literacy (CCHL). Grip strength, knee extension strength, toe-grip strength, sit-up test, sit-and-reach test, one-leg stance test time, 30-s chair-stand test (CS-30), and normal gait speed were measured. Subjects were divided into two groups based on normal gait speed-fast (speed ≥ 1.3 m/s) and slow (<1.3 m/s). In the logistic regression analysis, the dependent variable was normal gait speed (fast/slow). Four logistic regression models were utilized to determine whether health literacy affects gait speed. Height and CCHL were found to independently affect gait speed. That health literacy influences gait speed is a new discovery.

1,25-Dihydroxyvitamin D3 Inhibits Lipopolysaccharide-Induced Interleukin-6 Production by C2C12 Myotubes.

Background and Objective. 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) inhibits proinflammatory cytokines in microglial cells and monocytes. However, it is unclear whether 1,25(OH)2D3 inhibits proinflammatory cytokines in muscle cells. This study was conducted to investigate whether 1,25(OH)2D3 inhibits the production of proinflammatory cytokines, resulting in inhibition of the protein expression of E3 ubiquitin ligases and muscle protein loss. Materials and Methods. C2C12 myoblasts were proliferated in Dulbecco's modified Eagle medium (DMEM) containing 10% fetal bovine serum, and myoblasts were differentiated into myotubes in DMEM containing 2% horse serum. Myotubes were treated with 1,25(OH)2D3 for 24 h, followed by lipopolysaccharide (LPS) stimulation for 48 h. Results. Interleukin (IL)-6 protein concentrations were higher in the culture supernatant following LPS stimulation compared to that without LPS stimulation (p < 0.001). However, the IL-6 concentration was significantly lower in C2C12 myotubes following 1,25(OH)2D3 treatment than in C2C12 myotubes without 1,25(OH)2D3 treatment (p < 0.001). The myosin heavy chain (MHC), muscle atrophy F-box, and muscle ring-finger protein-1 protein levels did not significantly differ (P = 0.324, 0.552, and 0.352, respectively). We could not compare tumor necrosis factor α (TNFα) protein levels because they were below the limit of detection of our assay in many supernatant samples, including in LPS-stimulated samples. Conclusions. 1,25(OH)2D3 inhibited increases in IL-6 protein concentrations in muscle cells stimulated by LPS, suggesting that 1,25(OH)2D3 inhibits inflammation in muscle cells. The findings suggest that 1,25(OH)2D3 can prevent or improve sarcopenia, which is associated with IL-6. The TNFα protein content could not be measured, and MHC was not decreased despite LPS stimulation of C2C12 myotubes. Further studies are needed to examine the effects of higher doses of LPS stimulation on muscle cells and use more sensitive methods for measuring TNFα protein to investigate the preventive effects of 1,25(OH)2D3 on increased TNFα and muscle proteolysis.

Association of Low Bone Mass with Decreased Skeletal Muscle Mass: A Cross-Sectional Study of Community-Dwelling Older Women.

This study aimed to investigate the characteristics of skeletal muscle mass, muscle strength, and physical performance among community-dwelling older women. Data were collected from 306 older adults, and the data of 214 older women were included in the final analysis. Participants' calcaneus bone mass was measured using ultrasonography. Based on their T-scores, participants were divided into the following three groups: normal (T-score > -1), low (-2.5 < T-score ≤ -1), and very low (T-score ≤ -2.5) bone mass. Further, participants' skeletal muscle mass, muscle strength (grip and knee extension strength), and physical performance [gait speed and timed up and go (TUG)] were measured. Arm skeletal muscle index (SMI, skeletal muscle mass/height2), leg SMI, and appendicular SMI in the very low bone mass group were low compared to those of the low bone mass group (p = 0.034, p = 0.011, and p = 0.009, respectively). Grip and knee extension strength, gait speed, and TUG were not significantly different between the groups. These findings suggest that older women with low bone density had decreased skeletal muscle mass. Therefore, maintaining or improving skeletal muscle mass may prevent low bone mass.

Subjective and Objective Mental and Physical Functions Affect Subjective Cognitive Decline in Community-Dwelling Elderly Japanese People.

Subjective cognitive decline (SCD) is complex and not well understood, especially among Japanese people. In the present study, we aimed to elucidate the relationships of subjective and objective mental and physical function with SCD among older community-dwelling Japanese adults. SCD was evaluated using the Kihon Checklist: Cognitive Function. Other parameters were evaluated using the Mini-Mental State Examination (MMSE) and the five-item version of the Geriatric Depression Scale (GDS-5), for an objective mental function other than SCD. A timed up-and-go test (TUG) and knee extension strength were used to test objective physical function, and the Mental Component Summary (MCS) and Physical Component Summary (PCS) in the Health-Related Quality of Life survey eight-item short form (SF-8) were used for subjective mental and physical functions. The results of the MMSE, GDS-5, TUG, knee extension strength, and MCS were significantly worse in the SCD group. In addition, logistic regression analysis showed that GDS-5 and MCS were associated with SCD onset. Depressive symptoms and decreased subjective mental function contribute to SCD among community-dwelling Japanese adults. These findings will be useful for planning dementia prevention and intervention programs for older Japanese adults.

Increased Time Difference between Imagined and Physical Walking in Older Adults at a High Risk of Falling.

Walking motor imagery ability is thought to be associated with a fear of falling; however, no studies have compared fall risk and motor imagery ability. This study aimed to ascertain the time difference between imagined and physical walking in older adults at low and high risks of falling. Motor imagery ability was assessed using mental chronometry, which measures the imagined time required for movement. Participants included 31 older adults classified as having a high (n = 15) or low (n = 16) risk of falling based on single leg stance time. The time required for imagined and physical walking was measured using 5 m long walkways with three different widths (15, 25, and 50 cm), and the temporal errors (absolute and constant error) were compared. Physical walking time was significantly longer in the high-risk group than in the low-risk group for the 15 and 25 cm wide walkways. The absolute error between the imagined and physical walking times was significantly larger in the high-risk group than in the low-risk group for the 15 and 25 cm wide walkways. There was also a significant difference in the constant error between the high- and low-risk groups between the imagined and physical walking times for all three walkways. Older adults who may be at a higher risk of falling showed longer walking times during action execution but overestimated their performance (i.e., they believe they would be faster) during motor imagery. Therefore, the time difference between imagined and physical walking could, in part, be useful as a tool for assessing fall risk based on motor imagery.

Different patterns in age-related morphometric alteration of myelinated fibers and capillaries of the tibial nerve: a longitudinal study in normal rats.

Age-related regression of myelinated fibers in peripheral nerves of the lower limbs is strongly influenced by capillaries and results in balance dysfunction and falls. However, the temporal relationships between alteration patterns of myelinated fibers and capillaries have not yet been clarified. This study aimed to investigate age-related morphological and histological changes of both myelinated fibers and capillaries in peripheral nerves to clarify whether myelinated fibers or capillaries change earlier. Seven male Wistar rats each were randomly selected at 20 weeks (young group), 70 weeks (middle group), and 97 weeks (old group) for histological evaluations. The left and right tibial nerves were removed morphologically and histologically to examine myelinated fibers and capillaries. Axon diameter and myelin thickness were almost unaltered in the middle group compared with the young group but were significantly reduced in the old group when compared with the other two groups. However, the capillary diameter and number of microvascular branch points were substantially reduced in the middle group. The current study demonstrates that myelinated fibers of peripheral nerves show signs of regression in elderly rats, whereas capillaries start to reduce in middle-aged animals. In normal aging of the tibial nerve, capillaries may regress before myelinated fibers.

Endurance exercise increases the protein levels of PGC-1α and respiratory chain complexes in mouse skeletal muscle during atorvastatin administration.

Statins and exercise reduce cardiovascular disease incidence. We investigated whether endurance exercise in mice induces mitochondrial adaptation in skeletal muscle and muscle injury during administration of atorvastatin, a member of the statin medication class. Male C57BL mice were assigned to one of three groups: control (Con), statin (Statin), or statin and exercise (Statin + Ex). Atorvastatin was administered, and exercise performed on a treadmill for 8 weeks. The levels of mitochondria-associated proteins, PGC-1α, and respiratory chain complex, (COX) I-V, in the quadriceps femoris, and serum creatine kinase, a muscle injury marker, were measured. PGC-1α and COX I-V were upregulated in the Statin + Ex group compared to those in the Statin and Con groups; serum creatine kinase levels were similar. Endurance training in mice induced mitochondrial adaptation in skeletal muscle without causing muscle injury, during atorvastatin administration.

Effect of Skeletal Muscle and Fat Mass on Muscle Strength in the Elderly.

It is important for elderly people to maintain or improve muscle strength and for clinicians to know the factors that affect muscle strength. Therefore, the purpose of this study was to compare the effects of fat mass (FM) and skeletal muscle mass (SMM) on muscle strength. The participants included 192 community-dwelling elderly women. The SMM and FM, grip strength, and knee extension strength were measured. Data were evaluated using stepwise multiple linear regression analysis, which was performed with grip or knee extension strength as a dependent variable and the SMM and FM of the upper and lower limbs as the independent variables. The SMM and FM of the upper limbs were associated with grip strength, whereas the SMM but not the FM of the lower limbs was associated with knee extension strength. These findings suggest that there may be thresholds for the SMM/FM ratio to affect muscle strength.

Lectin Isolated from Japanese Red Sword Beans (Canavalia gladiata) as a Potential Cancer Chemopreventive Agent.

In this study, we investigated the chemical and biological profile of lectin isolated from Japanese red sword beans (Canavalia gladiata; RSBs). RSB lectin was purified using maltamyl-Sepharose 4B and subjected to amino acid composition and partial amino acid sequencing analyses, and evaluated for blood and carbohydrate specificity, mitogenic activity, splenic natural killer (NK) cell activity, and its effect on B16 melanoma cell proliferation, compared with Concanavalin A (Con A). The amino acid composition and sequences of RSB lectin were similar to those of Con A. RSB lectin showed specificity to mannose, glucose, maltose, methyl-D-mannoside, and thyroglobulin, but not rhamnose, using mouse, sheep, and rabbit erythrocytes. Compared with Con A, RSB lectin showed low resistance to proteases and to temperatures greater than 70 °C, but high mitogenic activity for mouse splenic cells. Notably, while treatment with RSB lectin and Con A (0.01 and 0.1 µg/mL) promoted similar levels of splenic NK cell activity, which were higher than that observed in the control (0 µg/mL) and interleukin 2 (IL-2) (25 U)-treated populations, RBS lectin exerted a significantly stronger anti-proliferative effect than Con A at a concentration of 125.0 µg per well. Overall, our results show that RSB lectin might exert immunological effects on mouse splenic cells and could thus be used as a potential cancer chemopreventive agent. PRACTICAL APPLICATION: Japanese red sword bean (RSB) is a tropical perennial legume consumed in many Asian countries. RSB lectin shows specificity to mannose, glucose, maltose, methyl-d-mannoside, and thyroglobulin, but not to rhamnose, using mouse, sheep, and rabbit erythrocytes. RSB lectin exhibits similarities to Concanavalin A in amino acid composition and sequence, shows mitogenic activity for mouse splenic cells and strong anti-proliferative activity for B16 melanoma cells, and also enhances the activity of splenic natural killer (NK) cells against YAC-1 cells. Thus, RSB lectin has the potential to be used as a bioactive protein in medical research.

Physical Characteristics Vary According to Body Mass Index in Japanese Community-Dwelling Elderly Women.

BACKGROUND: Body mass index (BMI) is related to health in the elderly. The purpose of this study was to investigate the physical characteristics in underweight, overweight, and obese Japanese community-dwelling elderly women compared to normal-weight elderly women. METHODS: The study participants included 212 community-dwelling elderly women. They were categorized as underweight (BMI < 18.5), normal weight (18.5 ≤ BMI ≤ 22.9), overweight (23 ≤ BMI ≤ 24.9), and obese (BMI ≥ 25). Data on skeletal muscle mass index (SMI), number of trunk curl-ups performed within 30 seconds, knee extension strength, one-leg standing time, and walking speed were recorded. RESULTS: In the underweight group, the number of trunk curl-ups was significantly lower than that of the normal-weight group (p = 0.011) and the correlation between knee extension strength and walking speed was relatively higher than in the normal-weight group (r = 0.612 vs. r = 0.471). In the overweight group, the SMI was significantly increased (p < 0.001), but knee extension strength was not increased (p = 0.235) compared to that of the normal-weight group. In the obese group, one-leg standing time was significantly shorter than in the normal-weight group (p = 0.016). CONCLUSIONS: Physical characteristics vary according to BMI and these findings are useful in assessing and planning interventional programs to improve and maintain physical function in elderly women.

Effects of Hull Scratching, Soaking, and Boiling on Antinutrients in Japanese Red Sword Bean (Canavalia gladiata).

The effects of hull processing, soaking, and boiling on the content or activity of antinutrients in the red sword bean (RSB; Canavalia gladiata) were investigated. RSB seeds were compared with kidney bean (KB; Phaseolus vulgaris) seeds that are starch based and often used as processed products in Japan. RSB seeds had higher weight, thicker hull, and higher protein content, but lower moisture content compared with KB seeds. Because of the strong and thick hull, the relative water absorption of untreated RSB seeds was very low after soaking. Seeds were soaked after dehulling, scratching, and roasting. The results showed that hull scratching was the optimal method for increasing water absorption during soaking compared with dehulling and roasting. After soaking, the water used for soaking was discarded, since it had a high content of polyphenols and bitter taste, and RSB seeds were boiled in fresh water for 20, 40, and 60 min. The results showed that polyphenol and tannin contents, antioxidant activity, and hemagglutinating activity, as well as maltase, sucrase, and trypsin inhibitor activities in scratched RSB seeds decreased significantly after boiling compared with those in raw seeds, whereas amylase inhibitor activity showed no significant change. Overall, it was concluded that the combination of hull scratching, soaking, and boiling in fresh water can reduce thermal-stable or sensitive antinutrients in RSB and thus, significantly improve its nutritional value.

Electrical stimulation ventilatory feedback facilitates maintenance of a prolonged expiration pattern during exercise: A proof-of-concept study in healthy adults.

This study aimed at verifying the safety and effects of electrical stimulation ventilatory feedback (ESVF) to provide feedback during expiration, which may assist with breathing control in patients with chronic obstructive pulmonary disease (COPD). Because this is a new therapy, we examined the feasibility of the therapy in healthy adults. The 23 healthy adult participants were randomized into two groups: a stimulation group that received ESVF and a placebo group with the ESVF device attached, but not activated. Sensory stimulation was provided at a frequency of 20 Hz and pulse duration of 200 µs. During breathing training, participants practiced a prolonged expiration pattern and were instructed to maintain the breathing pattern during exercise. A variety of parameters such as respiratory time from the gas analyzer monitor and quantitative load were measured during lower-extremity cycle ergometer exercise. The primary outcome was the expiratory to inspiratory time ratio, which was significantly higher in the stimulation group than in the placebo group, both during and after exercise. No side effects were reported during the use of electrical stimulation. Therefore, ESVF is safe and facilitates maintenance of a prolonged expiration pattern during and after exercise.

Surface electromyography activity of the rectus abdominis, internal oblique, and external oblique muscles during forced expiration in healthy adults.

We aimed to characterize rectus abdominis, internal oblique, and external oblique muscle activity in healthy adults under expiratory resistance using surface electromyography. We randomly assigned 42 healthy adult subjects to 3 groups: 30%, 20%, and 10% maximal expiratory intraoral pressure (PEmax). After measuring 100% PEmax and muscle activity during 100% PEmax, the activity and maximum voluntary contraction of each muscle during the assigned experimental condition were measured. At 100% PEmax, the external oblique (p<0.01) and internal oblique (p<0.01) showed significantly elevated activity compared with the rectus abdominis muscle. Furthermore, at 20% and 30% PEmax, the external oblique (p<0.05 and<0.01, respectively) and the internal oblique (p<0.05 and<0.01, respectively) showed significantly elevated activity compared with the rectus abdominis muscle. At 10% PEmax, no significant differences were observed in muscle activity. Although we observed no significant difference between 10% and 20% PEmax, activity during 30% PEmax was significantly greater than during 20% PEmax (external oblique: p<0.05; internal oblique: p<0.01). The abdominal oblique muscles are the most active during forced expiration. Moreover, 30% PEmax is the minimum intensity required to achieve significant, albeit very slight, muscle activity during expiratory resistance.