Ken Kouda

Acute limb heating improves macro- and microvascular dilator function in the leg of aged humans

Local heating of an extremity increases blood flow and vascular shear stress throughout the arterial tree. Local heating acutely improves macrovascular dilator function in the upper limbs of young healthy adults through a shear stress-dependent mechanism but has no such effect in the lower limbs of this age group. The effect of acute limb heating on dilator function within the atherosclerotic prone vasculature of the lower limbs of aged adults is unknown. Therefore, the purpose of this study was to test the hypothesis that acute lower limb heating improves macro- and microvascular dilator function within the leg vasculature of aged adults. Nine young and nine aged adults immersed their lower limbs at a depth of ~33 cm into a heated (~42°C) circulated water bath for 45 min. Before and 30 min after heating, macro (flow-mediated dilation)- and microvascular (reactive hyperemia) dilator functions were assessed in the lower limb, following 5 min of arterial occlusion, via Doppler ultrasound. Compared with preheat, macrovascular dilator function was unchanged following heating in young adults (P = 0.6) but was improved in aged adults (P = 0.04). Similarly, microvascular dilator function, as assessed by peak reactive hyperemia, was unchanged following heating in young adults (P = 0.1) but was improved in aged adults (P < 0.01). Taken together, these data suggest that acute lower limb heating improves both macro- and microvascular dilator function in an age dependent manner. NEW & NOTEWORTHY We demonstrate that lower limb heating acutely improves macro- and microvascular dilator function within the atherosclerotic prone vasculature of the leg in aged adults. These findings provide evidence for a potential therapeutic use of chronic lower limb heating to improve vascular health in primary aging and various disease conditions.

Age-related sex differences in erector spinae muscle endurance using surface electromyographic power spectral analysis in healthy humans.

BACKGROUND CONTEXT Previous studies reported that the erector spinae muscle is more resistant to fatigue in healthy adult women than in men. However, no study has reported changes in back muscle fatigue with aging in healthy men and women. PURPOSE The aim of this study was to evaluate age-related changes in muscle fatigue of erector spinae muscle in men and women. STUDY DESIGN/SETTING This cross-sectional study was conducted in a laboratory. PATIENT SAMPLE Fifty-three healthy subjects (11 elderly men, 11 elderly women, 17 young men, and 14 young women) without low back pain history. OUTCOME MEASURES The median frequency (MF) and mean power frequency (MPF) during trunk holding test were derived from the raw electromyographic (EMG) signal using Fast Fourier Transform spectrum analysis program. The rates of changes in MF and MPF were calculated. METHODS Subjects performed the unsupported trunk holding test until exhaustion. The results of power spectral analysis of the EMG activity of the left erector spinae muscle were compared in both age groups and sexes. RESULTS The endurance time in young men was significantly shorter than in young women. The slopes of MF and MPF in young men were significantly higher than in young women. There were no significant differences in MF and MPF slopes of elderly men and elderly women. Furthermore, the MF and MPF slopes were significantly lower in elderly men than young men but similar in the two women groups. CONCLUSIONS Age-related changes in the slopes of MF and MPF of erector spinae muscle occur in healthy men but not in healthy women.

A dysphagia study in patients with sporadic inclusion body myositis (s-IBM)

The nature of the swallowing impairment in patients with sporadic inclusion body myositis (s-IBM) has not been well characterized. In this study, we examined ten consecutive s-IBM patients using videofluoroscopy (VF) and computed pharyngoesophageal manometry (CPM). The patients were divided into two groups: patients with complaint and without complaint of dysphagia. VF results indicated pharyngeal muscle propulsion (PP) at the hypopharyngeal and upper esophagus sphincter (UES) in all s-IBM patients. Patients without complaint of dysphagia showed a mild degree of PP, whereas a severe form of PP was observed in patients with complaint of dysphagia. CPM revealed that negative pressure during UES opening was not observed in the s-IBM patients with complaint of dysphagia. Incomplete opening and PP at the UES were observed in all s-IBM patients. These results indicate that the dysphagic processes occur subclinically in s-IBM patients who may not report swallowing impairments.

Balloon Dilation in sporadic Inclusion Body Myositis patients with Dysphagia

Here, we describe balloon catheter dilation at the upper esophageal sphincter (UES) in three sporadic inclusion body myositis (s-IBM) patients with dysphagia. Initially, we performed IVIg therapy, and, three months later, switched to balloon dilation therapy. A 12-Fr balloon catheter was inserted from the mouth under fluoroscopy and the balloon inflated at the UES. The catheter was pulled back and re-inserted several times. We examined videofluoroscopy (VF) and pressure at the oropharynx, hypopharynx and UES using computed pharyngoesophageal manometry (CPM). Before both therapies, the VF study revealed a very small amount of barium paste passing through the UES. After balloon dilation therapy, as well as IVIg, subjective complaints of dysphagia disappeared and the VF study revealed an increased amount of barium paste passing through the UES. We conclude that balloon dilation therapy is a complementary method for conventional dysphagia therapies in s-IBM patients with dysphagia.

The role of cardiac sympathetic innervation and skin thermoreceptors on cardiac responses during heat stress

The mechanism(s) for the changes in cardiac function during heat stress remain unknown. This study tested two unique hypotheses. First, sympathetic innervation to the heart is required for increases in cardiac systolic function during heat stress. This was accomplished by comparing responses during heat stress between paraplegics versus tetraplegics, with tetraplegics having reduced/absent cardiac sympathetic innervation. Second, stimulation of skin thermoreceptors contributes to cardiovascular adjustments that occur during heat stress in humans. This was accomplished by comparing responses during leg only heating between paraplegic versus able-bodied individuals. Nine healthy able-bodied, nine paraplegics, and eight tetraplegics participated in this study. Lower body (i.e., nonsensed area for para/tetraplegics) was heated until esophageal temperature had increased by ~1.0°C. Echocardiographic indexes of diastolic and systolic function were performed before and at the end of heat stress. The heat stress increased cardiac output in all groups, but the magnitude of this increase was attenuated in the tetraplegics relative to the able-bodied (1.3 ± 0.4 vs. 2.3 ± 1.0 l/min; P < 0.05). Diastolic function was maintained in all groups. Indexes of left atrial and ventricular systolic function were enhanced in the able-bodied, but did not change in tetraplegics, while these changes in paraplegics were attenuated relative to the able-bodied. These data suggest that the cardiac sympathetic innervation is required to achieve normal increases in cardiac systolic function during heat stress but not required to maintain diastolic function during this exposure. Second, elevated systolic function during heat stress primarily occurs as a result of increases in internal temperature, although stimulation of skin thermoreceptors may contribute.

Wheelchair marathon creates a systemic anti-inflammatory environment in persons with spinal cord injury.

Objective:To investigate interleukin (IL)-6 and other inflammation markers in athletes with spinal cord injury (SCI) during a wheelchair marathon race. Design:Nonrandomized study in an actual race. Setting:The 28th Oita International Wheelchair Marathon Race, Japan. Participants:Twenty-eight men with SCI between T7 and L2 (16 full-marathon racers, full-group; and 12 half-marathon racers, half-group). Main Outcome Measures:Plasma IL-6, tumor necrosis factor (TNF)-&agr;, and high-sensitivity C-reactive protein (hsCRP) were measured the day before, immediately after the race, and 2 hours after the race. Results:Plasma IL-6 concentrations increased by 18.4-fold and by 9.4-fold (P < 0.05) in the full- and half-groups immediately after the race (P < 0.05), respectively, but returned to baseline at 2 hours of recovery. In contrast, plasma TNF-&agr; and hsCRP did not change throughout the race in both groups. The fold change in plasma IL-6 immediately after the race relative to the prerace was significantly higher in the full-group than the half-group (P < 0.05). In both groups, plasma IL-6 immediately after the race did not correlate with the average wheelchair speed. Interestingly, plasma IL-6 and hsCRP before the race in the full-group, but not in half-group, correlated negatively with the average wheelchair speed (P < 0.05). Conclusions:The study demonstrated that half- and full-marathon wheelchair races increased plasma IL-6, but not TNF-&agr; and hsCRP. Furthermore, the top athletes of the full-group had low plasma IL-6 and hsCRP at baseline. Wheelchair marathon competition, especially full-marathon, and daily training seem to have beneficial effects on SCI through the plasma IL-6 response.

Age Modulates Physiological Responses during Fan Use under Extreme Heat and Humidity

Purpose We examined the effect of electric fan use on cardiovascular and thermoregulatory responses of nine young (26 ± 3 yr) and nine aged (68 ± 4 yr) adults exposed to extreme heat and humidity. Methods While resting at a temperature of 42°C, relative humidity increased from 30% to 70% in 2% increments every 5 min. On randomized days, the protocol was repeated without or with fan use. HR, core (Tcore) and mean skin (Tsk) temperatures were measured continuously. Whole-body sweat loss was measured from changes in nude body weight. Other measures of cardiovascular (cardiac output), thermoregulatory (local cutaneous and forearm vascular conductance, local sweat rate), and perceptual (thermal and thirst sensations) responses were also examined. Results When averaged over the entire protocol, fan use resulted in a small reduction of HR (−2 bpm, 95% confidence interval [CI], −8 to 3), and slightly greater Tcore (+0.05°C; 95% CI, −0.13 to 0.23) and Tsk (+0.03°C; 95% CI, −0.36 to 0.42) in young adults. In contrast, fan use resulted in greater HR (+5 bpm; 95% CI, 0–10), Tcore (+0.20°C; 95% CI, 0.00–0.41), and Tsk (+0.47°C; 95% CI, 0.18–0.76) in aged adults. A greater whole-body sweat loss during fan use was observed in young (+0.2 kg; 95% CI, −0.2 to 0.6) but not aged (0.0 kg; 95% CI, −0.2 to 0.2) adults. Greater local sweat rate and cutaneous vascular conductance were observed with fan use in aged adults. Other measures of cardiovascular, thermoregulatory, and perceptual responses were unaffected by fan use in both groups. Conclusions During extreme heat and humidity, fan use elevates physiological strain in aged, but not young, adults.

Folic acid ingestion improves skeletal muscle blood flow during graded handgrip and plantar flexion exercise in aged humans

Skeletal muscle blood flow is attenuated in aged humans performing dynamic exercise, which is due, in part, to impaired local vasodilatory mechanisms. Recent evidence suggests that folic acid improves cutaneous vasodilation during localized and whole body heating through nitric oxide-dependent mechanisms. However, it is unclear whether folic acid improves vasodilation in other vascular beds during conditions of increased metabolism (i.e., exercise). The purpose of this study was to test the hypothesis that folic acid ingestion improves skeletal muscle blood flow in aged adults performing graded handgrip and plantar flexion exercise via increased vascular conductance. Nine healthy, aged adults (two men and seven women; age: 68 ± 5 yr) performed graded handgrip and plantar flexion exercise before (control), 2 h after (acute, 5 mg), and after 6 wk (chronic, 5 mg/day) folic acid ingestion. Forearm (brachial artery) and leg (superficial femoral artery) blood velocity and diameter were measured via Duplex ultrasonography and used to calculate blood flow. Acute and chronic folic acid ingestion increased serum folate (both P < 0.05 vs. control). During handgrip exercise, acute and chronic folic acid ingestion increased forearm blood flow (both conditions P < 0.05 vs. control) and vascular conductance (both P < 0.05 vs. control). During plantar flexion exercise, acute and chronic folic acid ingestion increased leg blood flow (both P < 0.05 vs. control), but only acute folic acid ingestion increased vascular conductance (P < 0.05 vs. control). Taken together, folic acid ingestion increases blood flow to active skeletal muscle primarily via improved local vasodilation in aged adults.NEW & NOTEWORTHY Our findings demonstrate that folic acid ingestion improves blood flow via enhanced vascular conductance in the exercising skeletal muscle of aged humans. These findings provide evidence for the therapeutic use of folic acid to improve skeletal muscle blood flow, and perhaps exercise and functional capacity, in human primary aging.Listen to this articles corresponding podcast at http://ajpheart.podbean.com/e/folic-acid-and-exercise-hyperemia-in-aging/.

Differences in serum IL-6 response after 1 °C rise in core body temperature in individuals with spinal cord injury and cervical spinal cord injury during local heat stress

Abstract Objectives: Passive rise in core body temperature achieved by head-out hot water immersion (HHWI) results in acute increases in serum interleukin (IL)-6 but no change in plasma adrenaline in patients with cervical spinal cord injury (CSCI). The purpose of the present study was to determine the mechanism of heat stress-induced increase in serum IL-6. Setting: A cross-sectional study. Methods: The study subjects were nine with CSCI, ten with thoracic and lumbar spinal cord injury (TLSCI) and eight able-bodied (AB) subjects. Time since injury was 16.1 ± 3.4 years in TLSCI and 16.4 ± 4.1 years in CSCI. Subjects were subjected to lower-body heat stress (LBH) by wearing a hot water-perfused suit until 1 °C increase in core temperature. The levels of serum IL-6, plasma adrenaline, tumour necrosis factor (TNF)-α, C-reactive protein (CRP), and counts of blood cells were measured at normothermia and after LBH. Results: Serum IL-6 concentrations increased significantly immediately after LBH in all the three groups. ΔIL-6% was lower in CSCI subjects compared with AB subjects. Plasma adrenaline concentrations significantly increased after LBH in AB and TLSCI subjects, but did not change throughout the study in CSCI subjects. Cardiac output and heart rate increased at the end of LBH in all three groups. Conclusions: Under a similar increase in core temperature, ΔIL-6% was lower in the CSCI group compared with the AB group. These findings suggest that the observed rise in IL-6 during hyperthermia is mediated, at least in part, by plasma adrenaline.

Folic acid supplementation does not attenuate thermoregulatory or cardiovascular strain of older adults exposed to extreme heat and humidity

What is the central question of this study? Does folic acid supplementation alleviate thermoregulatory and cardiovascular strain of older adults during exposure to extreme heat and humidity? What is the main finding and its importance? Folic acid supplementation for 6 weeks did not affect whole‐limb blood flow/vasodilatation, core and skin temperatures, heart rate, blood pressure and cardiac output. Thus, 6 weeks of folic acid supplementation does not alleviate thermoregulatory or cardiovascular strain of healthy older adults exposed to extreme heat and humidity.