Frontiers in Physiology最新文献

Background: Vocal therapy, such as singing training, is an increasingly popular pulmonary rehabilitation program that has improved respiratory muscle status in patients with chronic obstructive pulmonary disease (COPD). However, variations in singing treatment protocols have led to inconsistent clinical outcomes.

Objective: This study aims to explore the content of vocalization training for patients with COPD by observing differences in respiratory muscle activation across different vocalization tasks.

Methods: All participants underwent measurement of surface electromyography (sEMG) activity from the sternocleidomastoid (SCM), parasternal intercostal muscle (PARA), seventh intercostal muscle (7thIC), and rectus abdominis (RA) during the production of the vowels/a/,/i/, and/u/at varying pitches (comfortable, +6 semitones) and loudness (-10 dB, +10 dB) levels. The Visual Analog Scale (VAS) was used to evaluate the condition of patients concerning vocalization, while the Borg-CR10 breathlessness scale was utilized to gauge the level of dyspnea following the task. Repeated-measure (RM) ANOVA was utilized to analyze the EMG data of respiratory muscles and the Borg scale across different tasks.

Results: Forty-one patients completed the experiment. Neural respiratory drive (NRD) in the SCM muscle did not significantly increase at high loudness levels (VAS 7-8) compared with that at low loudness levels (F (2, 120) = 1.548, P = 0.276). However, NRD in the PARA muscle (F (2, 120) = 55.27, P< 0.001), the 7thIC muscle (F (2, 120) = 59.08, P < 0.001), and the RA muscle (F (2, 120) = 39.56, P < 0.001) were significantly higher at high loudness compared with that at low loudness (VAS 2-3). Intercostal and abdominal muscle activation states were negatively correlated with maximal expiratory pressure (r = -0.671, P < 0.001) and inspiratory pressure (r = -0.571, P < 0.001) in the same loudness.

Conclusion: In contrast to pitch or vowel, vocal loudness emerges as a critical factor for vocalization training in patients with COPD. Higher pitch and loudness produced more dyspnea than lower pitch and loudness. In addition, maximal expiratory/inspiratory pressure was negatively correlated with respiratory muscle NRD in the same loudness vocalization task.

Breath-hold diving performances are typically better in men than in women. However, it is still being determined if there are differences in the physiological responses to breath-holding between the sexes. We conducted a study comparing the maximum breath-hold duration, heart rate (HR) reduction, peripheral oxygen saturation (SpO₂), and spleen volume and contraction in 37 men and 44 women, all of whom had no prior breath-holding experience. They performed two dry apneas separated by 2 min; the first was limited to 60 s, followed by a maximal effort apnea. HR and SpO₂ were measured continuously. Spleen diameters were measured via ultrasonography before and immediately following each apnea. The maximal apneic duration was longer in men (78 ± 19 s) compared with women (61 ± 18 s, p < 0.001), while the HR reduction was similar (women: 16% ± 19% versus men: 16% ± 17%, p = 0.973). The absolute splenic contraction was greater in men (59 ± 56 mL) compared with women (35 ± 28 mL, p < 0.001) in the first apnea, while the relative contraction was similar (women: 21% ± 17% versus men: 23% ± 13%, p = 0.528). In addition, the lowest SpO₂ during the maximal apnea was similar between sexes (women: 93.3% ± 4.4%; men: 91.9% ± 4.3%, p = 0.161). We conclude that men have larger spleen size and contraction, lung size, and maximal apneic duration than women. The cardiovascular diving response is similar between sexes for those inexperienced with apneic diving. The longer breath-hold duration in men may be partly due to greater oxygen storage capacity, which results from larger vital capacity and greater spleen size and contraction.

Purpose: To explore the relationships between performance variables and physiological variables in a short-time (2-3 min) cycling time trial (TT) on a cycle ergometer.

Methods: Fifteen young elite cyclists (age: 17.3 ± 0.7 years, maximal oxygen uptake (VO_2max): 76.6 ± 5.2 mL⋅kg^-1⋅min^-1) participated in this study. Maximal aerobic power (MAP), maximal anaerobic power (MANP), time to exhaustion at 130% of maximal aerobic power (TTE), maximal accumulated oxygen deficit (MAOD) in the TT, anaerobic power reserve (APR) and lactate threshold (LT) was tested. MAP was calculated as VO_2max/oxygen cost of cycling (C_C), MANP was determined as mean power output (W) during a 10 s maximal cycling sprint test, and MAOD was calculated as (VO₂ demand - VO₂ measured) ∙ time. APR was calculated as the relative difference between MAP and MANP.

Results: There was a strong correlation between MAP and TT time (r = -0.91, p < 0.01) with a standard error of estimate (SEE) of 4.4%, and a moderate association between MANP and TT time (r = -0.47, p = 0.04). Neither MAOD, TTE, LT nor APR correlated with TT.

Conclusion: MAP was highly correlated with TT with a SEE of 4.4%. Since neither TTE nor MAOD correlated with TT, this indicates that these two variables do not play a significant role in differentiating short-time endurance cycling performance. We suggest training for improving MAP and, or MANP to improve short-time endurance cycling performance.

Purpose: The purpose of this study was to determine the relationship between linear and change-of-direction sprinting performance with dribbling performance and Dribble Deficit in professional female handball players.

Methods: Eleven professional female handball players (mean age: 21.12 ± 4.34 years; body height: 171.59 ± 4.52 cm; body weight: 66.29 ± 5.73 kg) participated in the study. Each participant completed several linear (sprint over 10, 20, and 30 m) and change-of-direction tests (slalom test, zig-zag test, 505 test), first without the ball (sprinting performance) followed by ball dribbling (dribbling performance). Dribble Deficit was calculated indirectly as the time difference between the best trial while dribbling minus the best trial without dribbling.

Results: A large to very large correlation was observed between the linear sprint and dribbling performance (r = 0.53-0.78), as well as between change-of-direction sprinting performance and dribbling performance (r = 0.66-0.88). The study also showed a moderate to perfect relationship between linear dribbling performance and Dribble Deficit (r = 0.46-0.93), and a large relationship between change-of-direction dribbling performance and Dribble Deficit (r = 0.54-0.55), while the relationships between linear sprinting performance and Dribble Deficit (r = -0.51-0.21) and between change-of-direction sprinting performance and Dribble Deficit (r = -0.14-0.26) were small and non-significant.

Conclusion: In summary, Dribble Deficit reflects dribbling ability independent of sprinting ability and refines its application for practical use in assessing dribbling skills in female handball players.

Stellate ganglion blockade (SGB) is a practical approach to managing many clinical disorders. Ultrasound-guided SGB is currently adopted as a more effective and safer method in humans. Developing this technique in rats would facilitate further study of SGB application. The present study examined physiological responses following ultrasound-guided SGB in Sprague-Dawley rats. Under general anesthesia, lidocaine containing Chicago blue dye (1.0%-1.5% in 40-60 µL) was injected into the unilateral stellate ganglion (SG). Ptosis was observed on the ipsilateral right (n = 8) or left (n = 7) side of lidocaine administration. No ptosis was noted in any controls by 0.9% normal saline injection into the right (n = 6) or left (n = 6) SG. Heart rate (HR) was significantly decreased after administration of lidocaine (344 ± 32 to 289 ± 47 bpm; p = 0.015, pre-vs. after-injection), but not after normal saline, into the right SG. HR was unaltered after injecting lidocaine or normal saline into the left SG. Heart rate variability analysis showed that SGB with lidocaine on the right or left side caused a decrease in the ratio of the power of low-frequency over high-frequency. Respiratory rate, body temperature, and general conditions were unchanged in all rats, regardless of left or right SGB. Chicago blue dye was confirmed to be distributed in the SG region. No bleeding or tissue damage was evident in the injected SG area. Our findings suggest that ultrasound-guided unilateral SGB effectively inhibits cervicothoracic sympathetic nerves in rats and enhances heart rate variability, and sympathetic nerves controlling HR are likely predominantly associated with the right SG in the rat.

Two-pore channels (TPCs) are adenine nucleotide and phosphoinositide regulated cation channels. NAADP activates and ATP blocks TPCs, while the endolysosomal phosphoinositide PI(3,5)P₂ activates TPCs. TPCs are ubiquitously expressed including expression in the innate as well as the adaptive immune system. In the immune system TPCs are found, e.g. in macrophages, mast cells and T cells. In cytotoxic T cells, NAADP activates TPCs on cytolytic granules to stimulate exocytosis and killing. TPC inhibition or knockdown increases the number of regulator T cells in a transmembrane TNF/TNFR2 dependent manner, contributing to anti-inflammatory effects in a murine colitis model. TPC1 regulates exocytosis in mast cells in vivo and ex vivo, and TPC1 deficiency in mast cells augments systemic anaphylaxis in mice. In bone marrow derived macrophages NAADP regulates TPCs to control phagocytosis in a calcineurin/dynamin dependent manner, which was recently challenged by data, claiming no effect of TPCs on phagocytosis in macrophages but instead a role in phagosome resolution, a process thought to be mediated by vesiculation and tubulation. In this review we will discuss evidence and recent findings on the different roles of TPCs in immune cell function as well as evidence for adenine nucleotides being involved in these processes. Since the adenine nucleotide effects (NAADP, ATP) are mediated by auxiliary proteins, respectively, another major focus will be on the complex network of TPC regulatory proteins that have been discovered recently.

Nitric oxide (NO) is a ubiquitous signaling molecule known to modulate various physiological processes, with specific implications in skeletal muscle and broader applications in exercise performance. This review focuses on the modulation of skeletal muscle function, mitochondrial adaptation and function, redox state by NO, and the effect of nitrate supplementation on exercise performance. In skeletal muscle function, NO is believed to increase the maximal shortening velocity and peak power output of muscle fibers. However, its effect on submaximal contraction is still undetermined. In mitochondria, NO may stimulate biogenesis and affect respiratory efficiency. NO also plays a role in the redox state within the skeletal muscle, partially through its interaction with respiratory chain enzymes and transcriptional regulators of antioxidant production. Nitrate supplementation leads to an increased bioavailability of NO in skeletal muscle. Thus, nitrate supplementation has been investigated for its ability to impact performance outcomes in endurance and resistance exercise. The effect of nitrate supplementation on endurance exercise is currently indecisive, although evidence indicates that it may extend the time to exhaustion in endurance exercise. Alternatively, the effect of nitrate supplementation on resistance exercise performance has been less studied. Limited research indicates that nitrate supplementation may improve repetitions to failure. Further research is needed to investigate the influence of training status, age, sex, and duration of supplementation to further elucidate the impact of nitrate supplementation on exercise performance.

Introduction: Proprioceptive neuromuscular facilitation (PNF) stretching is widely used to increase range of motion, but its underlying mechanisms are not well understood. This experimental, parallel group design study investigated the acute effects of PNF stretching on rectus femoris muscle stiffness and explored a potential dose-response relationship.

Methods: Thirty healthy young adults (23 females, 7 males) were randomly assigned to either a PNF stretching group (n = 15; 22.96 ± 2.2 years) or a control group (n = 15; 23.3 ± 2.1 years). Rectus femoris stiffness was measured using shear-wave elastography (Resona 7, Mindray, China) at two locations (distal and proximal) before and after the second, fourth, and sixth sets of PNF stretching. The protocol involved six sets, each with three 10-s stretches and 5-s maximal contractions.

Results: The results indicate that PNF stretching had no statistically significant effect on muscle stiffness, with no main effects of group (F = 0.05; p = 0.830) or time (F = 0.545; p = 0.653), and no significant interactions. However, the proximal location showed a substantially higher shear modulus compared to the distal location (F = 63.6; p < 0.001; η² = 0.69), independent of group or time.

Discussion: These findings highlight a location-specific difference in muscle stiffness that was unaffected by the intervention. In conclusion, PNF stretching did not acutely reduce rectus femoris stiffness compared to passive rest, regardless of the number of stretching sets performed. Further research is needed to understand the muscle-specific effects of PNF stretching.

Competitive alpine skiing requires a high level of physical fitness to perform sport-specific manoeuvres and to minimise the risk of injury. The aim of this study was to establish reference values for the maximal anatomical cross-sectional area (ACSA_max) of the individual hamstrings (HAM) and quadriceps (QUAD) muscles as well as for the maximal voluntary torque (MVT) during knee flexion (KF) and knee extension (KE) of female and male elite competitive alpine skiers. Ultrasound and dynamometer data were obtained from a largely overlapping but not identical dataset. The ultrasound data were collected from 33 elite alpine skiers (20 women and 13 men), and the dynamometer data were collected from 35 elite alpine skiers (20 women and 15 men). Compared with female skiers, male skiers presented a significantly greater ACSA_max in the biceps femoris short head (BFsh), biceps femoris long head (BFlh), and semitendinosus (ST) muscles, as well as in the entire HAM muscle group. The ACSA_max of the semimembranosus (SM) did not differ significantly between the two sexes. Compared with female skiers, male skiers presented significantly greater ACSA_max values in the vastus lateralis (VL), rectus femoris (RF), vastus medialis (VM) and entire QUAD muscle groups. At VI, there was no significant difference in the ACSA_max between the two sexes. Compared with male skiers, female skiers had a significantly greater proportional SM ACSA_max. In terms of MVT, male skiers presented greater absolute and relative values than females did. There were no differences in the MVT/ACSA_max between the sexes. Neither the HAM/QUAD ACSA_max ratio nor the KF/KE MVT ratio differed between the sexes. The present study provides normative values for the muscle size and strength of the HAM and QUAD muscles of elite competitive alpine skiers. These values can be used as benchmarks for youth alpine skiers striving for the elite level. An interesting finding of the present study was that female skiers had a greater proportional ACSA_max of the SM, as this may be relevant in anterior cruciate ligament injury prevention given the function of tibia internal rotation.