Near-infrared spectroscopy measures of sternocleidomastoid blood flow during exercise and hyperpnoea

Effects of High-Intensity Inspiratory Muscle Warm-Up on High-Intensity Exercise Performance and Muscle Oxygenation

PURPOSE

An inspiratory muscle warm-up (IMW) improves inspiratory muscle function, but the effects of high-intensity exercise are inconsistent. We aimed to determine the effects of high-intensity IMW on high-intensity exercise performance and muscle oxygenation.

METHODS

Ten healthy men (maximal oxygen uptake [V˙O2max] 52.2 [5.0] mL·kg-1·min-1) performed constant-load exercise to exhaustion on a cycle ergometer at V˙O2max under 2 IMW conditions: a placebo condition (PLA) and a high-intensity IMW condition (HIGH). The inspiratory loads were set at 15% and 80% of maximal inspiratory pressure, respectively. Maximal inspiratory pressure was measured before and after IMW. Oxyhemoglobin was measured in the vastus lateralis by near-infrared spectroscopy during exercise. Rating of perceived exertion (RPE) for a leg was measured after 1 and 2 minutes of exercise.

RESULTS

Exercise tolerance was significantly higher under HIGH than PLA (228 [49] s vs 218 [49] s, P = .003). Maximal inspiratory pressure was significantly increased by IMW under HIGH (from 125 [20] to 136 [25] cm H2O, P = .031). Oxyhemoglobin was significantly higher under HIGH than PLA at 80% of the total duration of exercise (P = .048). RPE for the leg was significantly lower under HIGH than PLA after 2 minutes of exercise (P = .019).

CONCLUSIONS

Given that oxyhemoglobin is an index of local oxygen supply, the results of this study suggest that high-intensity IMW increases the oxygen supply to active limbs. It may also reflect a reduction in RPE in the leg. In addition, high-intensity IMW may improve exercise performance.

Ultrasonic detection of vagus, accessory, and phrenic nerve atrophy in amyotrophic lateral sclerosis: Relation to impairment and mortality

BACKGROUND AND PURPOSE

In amyotrophic lateral sclerosis (ALS), phrenic nerve (PN) atrophy has been found, whereas there is controversy regarding vagus nerve (VN) atrophy. Here, we aimed to find out whether PN atrophy is related to respiratory function and 12-month survival. Moreover, we investigated the relevance of VN and spinal accessory nerve (AN) atrophy in ALS.

METHODS

This prospective observational monocentric study included 80 adult participants (40 ALS patients, 40 age- and sex-matched controls). The cross-sectional area (CSA) of bilateral cervical VN, AN, and PN was measured on high-resolution ultrasonography. Clinical assessments included the Amyotrophic Lateral Sclerosis Functional Rating Scale-Revised (ALSFRS-R), the Non-Motor Symptoms Questionnaire, and handheld spirometry of forced vital capacity (FVC). One-year survival was documented.

RESULTS

The CSA of each nerve, VN, AN, and PN, was smaller in ALS patients compared to controls. VN atrophy was unrelated to nonmotor symptom scores. PN CSA correlated with the respiratory subscore of the ALSFRS-R (Spearman test, r = 0.59, p < 0.001), the supine FVC (r = 0.71, p < 0.001), and the relative change of sitting-supine FVC (r = -0.64, p = 0.001). Respiratory impairment was predicted by bilateral mean PN CSA (p = 0.046, optimum cutoff value of ≤0.37 mm2 , sensitivity = 92%, specificity = 56%) and by the sum of PN and AN CSA (p = 0.036). The combination of ALSFRS-R score with PN and AN CSA measures predicted 1-year survival with similar accuracy as the combination of ALSFRS-R score and FVC.

CONCLUSIONS

Ultrasonography detects degeneration of cranial nerve motor fibers. PN and AN calibers are tightly related to respiratory function and 1-year survival in ALS.

Monitoring Changes in Oxygen Muscle during Exercise with High-Flow Nasal Cannula Using Wearable NIRS Biosensors

Exercise increases the cost of breathing (COB) due to increased lung ventilation (V˙E), inducing respiratory muscles deoxygenation (∇SmO2), while the increase in workload implies ∇SmO2 in locomotor muscles. This phenomenon has been proposed as a leading cause of exercise intolerance, especially in clinical contexts. The use of high-flow nasal cannula (HFNC) during exercise routines in rehabilitation programs has gained significant interest because it is proposed as a therapeutic intervention for reducing symptoms associated with exercise intolerance, such as fatigue and dyspnea, assuming that HFNC could reduce exercise-induced ∇SmO2. SmO2 can be detected using optical wearable devices provided by near-infrared spectroscopy (NIRS) technology, which measures the changes in the amount of oxygen bound to chromophores (e.g., hemoglobin, myoglobin, cytochrome oxidase) at the target tissue level. We tested in a study with a cross-over design whether the muscular desaturation of m.vastus lateralis and m.intercostales during a high-intensity constant-load exercise can be reduced when it was supported with HFNC in non-physically active adults. Eighteen participants (nine women; age: 22 ± 2 years, weight: 65.1 ± 11.2 kg, height: 173.0 ± 5.8 cm, BMI: 21.6 ± 2.8 kg·m-2) were evaluated in a cycle ergometer (15 min, 70% maximum watts achieved in ergospirometry (V˙O2-peak)) breathing spontaneously (control, CTRL) or with HFNC support (HFNC; 50 L·min-1, fiO2: 21%, 30 °C), separated by seven days in randomized order. Two-way ANOVA tests analyzed the ∇SmO2 (m.intercostales and m.vastus lateralis), and changes in V˙E and ∇SmO2·V˙E-1. Dyspnea, leg fatigue, and effort level (RPE) were compared between trials by the Wilcoxon matched-paired signed rank test. We found that the interaction of factors (trial × exercise-time) was significant in ∇SmO2-m.intercostales, V˙E, and (∇SmO2-m.intercostales)/V˙E (p < 0.05, all) but not in ∇SmO2-m.vastus lateralis. ∇SmO2-m.intercostales was more pronounced in CTRL during exercise since 5' (p < 0.05). Hyperventilation was higher in CTRL since 10' (p < 0.05). The ∇SmO2·V˙E-1 decreased during exercise, being lowest in CTRL since 5'. Lower dyspnea was reported in HFNC, with no differences in leg fatigue and RPE. We concluded that wearable optical biosensors documented the beneficial effect of HFNC in COB due to lower respiratory ∇SmO2 induced by exercise. We suggest incorporating NIRS devices in rehabilitation programs to monitor physiological changes that can support the clinical impact of the therapeutic intervention implemented.

Effects of high-intensity inspiratory muscle warm-up on inspiratory muscle strength and accessory inspiratory muscle activity

This study aimed to determine the effects of work-matched moderate-intensity and high-intensity inspiratory muscle warm-up (IMW) on inspiratory muscle strength and accessory inspiratory muscle activity. Eleven healthy men performed three IMWs at different intensities, namely, placebo, moderate-intensity, and high-intensity, set, respectively, at 15%, 40%, and 80% of maximal inspiratory mouth pressure (MIP). MIP was measured before and after IMW. Electromyography (EMG) was recorded for the sternocleidomastoid muscle (SCM) and intercostal muscles (IC) during IMW. MIP increased significantly in the moderate-intensity condition (104.2 ± 5.1%, p<0.05) and high-intensity condition (106.5 ± 6.2%, p<0.01) after IMW. The EMG amplitudes of the SCM and IC during IMW were significantly higher in the order of high-intensity, moderate-intensity, and placebo conditions. There was a significant correlation between changes in MIP and EMG amplitude of the SCM (r=0.60, p<0.01) and IC (r=0.47, p<0.01) during IMW. These findings suggest that high-intensity IMW increases neuromuscular activity in the accessory inspiratory muscles, which may improve inspiratory muscle strength.