Control of hyperpnoea and pulmonary gas exchange during prolonged exercise: The role of group III/IV muscle afferent feedback.

It remains unclear whether feedback from group III/IV muscle afferents is of continuous significance for regulating the pulmonary response during prolonged (>5 min), steady-state exercise. To elucidate the influence of these sensory neurons on hyperpnoea, gas exchange efficiency, arterial oxygenation and acid-base balance during prolonged locomotor exercise, 13 healthy participants (4 females; 21 (3) years, : 46 (8) ml/kg/min) performed consecutive constant-load cycling bouts at ∼50% (20 min), ∼75% (20 min) and ∼100% (5 min) of with intact (CTRL) and pharmacologically attenuated (lumbar intrathecal fentanyl; FENT) group III/IV muscle afferent feedback from the legs. Pulmonary responses were continuously recorded and arterial blood (radial catheter) periodically collected throughout the exercise.

Hypertension restricts leg blood flow and aggravates neuromuscular fatigue during human locomotion in males.

Patients with hypertension (HTN) are characterized by exaggerated vascular resistance and mean arterial pressure (MAP) and a compromised leg blood flow (Q) response to exercise recruiting a small muscle mass. However, the impact of hypertension on peripheral hemodynamics and the development of neuromuscular fatigue during locomotor activities, which critically depends on Q, remain unknown. Eight HTN (143 ± 11 mmHg/95 ± 6 mmHg; 45 ± 13 yr) and eight matched (age and activity) controls (120 ± 6 mmHg/77 ± 7 mmHg; CTRL) performed constant-load cycling exercise at 25, 50, and 75 W (for 4 min each) and at 165 ± 41 W (for 5 min).

The exercise pressor reflex - a pressure-raising mechanism with a limited role in regulating leg perfusion during locomotion in young healthy men.

We investigated the role of the exercise pressor reflex (EPR) in regulating the haemodynamic response to locomotor exercise. Eight healthy participants (23 ± 3 years, : 49 ± 6 ml/kg/min) performed constant-load cycling exercise (∼36/43/52/98% ; 4 min each) without (CTRL) and with (FENT) lumbar intrathecal fentanyl attenuating group III/IV locomotor muscle afferent feedback and, thus, the EPR. To avoid different respiratory muscle metaboreflex and arterial chemoreflex activation during FENT, subjects mimicked the ventilatory response recorded during CTRL.

Development of a computerized 2D rating scale for continuous and simultaneous evaluation of two dimensions of a sensory stimulus.

Introduction: One-dimensional rating scales are widely used in research and in the clinic to assess individuals' perceptions of sensory stimuli. Although these scales provide essential knowledge of stimulus perception, their limitation to one dimension hinders our understanding of complex stimuli.

Methods: To allow improved investigation of complex stimuli, a two-dimensional scale based on the one-dimensional Gracely Box Scale was developed and tested in healthy participants on a visual and an auditory task (rating changes in brightness and size of circles and rating changes in frequency and sound pressure of sounds, which was compared to ratings on one-dimensional scales).

On the haemodynamic consequence of the chemoreflex and muscle mechanoreflex interaction in women and men: two tales, one story.

The cardiovascular response resulting from the individual activation of the muscle mechanoreflex (MMR) or the chemoreflex (CR) is different between men and women. Whether the haemodynamic consequence resulting from the interaction of these sympathoexcitatory reflexes is also sex-dependent remains unknown. MMR and CR were activated by passive leg movement (LM) and exposure to hypoxia (O -CR) or hypercapnia (CO -CR), respectively.

Impact of aging on the work of breathing during exercise in healthy men.

This study examined the impact of aging on the elastic and resistive components of the work of breathing () during locomotor exercise at a given ) ventilatory rate, ) metabolic rate, and ) operating lung volume. Eight healthy younger (25 ± 4 yr) and 8 older (72 ± 6 yr) participants performed incremental bicycle exercise, from which retrospective analyses identified similar ventilatory rates (approximately 40, 70, and 100 L·min), similar metabolic rates (V̇o: approximately 1.2, 1.

On the implication of dietary nitrate supplementation for the hemodynamic and fatigue response to cycling exercise.

This study investigated the impact of dietary nitrate supplementation on peripheral hemodynamics, the development of neuromuscular fatigue, and time to task failure during cycling exercise. Eleven recreationally active male participants (27 ± 5 yr, V̇o: 42 ± 2 mL/kg/min) performed two experimental trials following 3 days of either dietary nitrate-rich beetroot juice (4.1 mmol NO/day; DNS) or placebo (PLA) supplementation in a blinded, counterbalanced order.

Vascular function in continuous-flow left ventricular assist device recipients: effect of a single pulsatility treatment session.

Vascular function is further attenuated in patients with chronic heart failure implanted with a continuous-flow left ventricular assist device (LVAD), likely due to decreased arterial pulsatility, and this may contribute to LVAD-associated cardiovascular complications. However, the impact of increasing pulsatility on vascular function in this population is unknown. Therefore, 15 LVAD recipients and 15 well-matched controls underwent a 45-min, unilateral, arm pulsatility treatment, evoked by intermittent cuff inflation/deflation (2-s duty cycle), distal to the elbow.

Ascorbate attenuates cycling exercise-induced neuromuscular fatigue but fails to improve exertional dyspnea and exercise tolerance in COPD.

We examined the effect of intravenous ascorbate (VitC) administration on exercise-induced redox balance, inflammation, exertional dyspnea, neuromuscular fatigue, and exercise tolerance in patients with chronic obstructive pulmonary disease (COPD). Eight COPD patients completed constant-load cycling (∼80% of peak power output, 83 ± 10 W) to task failure after intravenous VitC (2 g) or saline (placebo, PL) infusion. All participants repeated the shorter of the two exercise trials (isotime) with the other infusate.

The muscle reflex and chemoreflex interaction: ventilatory implications for the exercising human.

We examined the interactive influence of the muscle reflex (MR) and the chemoreflex (CR) on the ventilatory response to exercise. Eleven healthy subjects (5 women/6 men) completed three bouts of constant-load single-leg knee-extension exercise in a control trial and an identical trial conducted with lumbar intrathecal fentanyl to attenuate neural feedback from lower-limb group III/IV muscle afferents. The exercise during the two trials was performed while breathing ambient air ([Formula: see text] ~97%, [Formula: see text]~84 mmHg, [Formula: see text] ~32 mmHg, pH ~7.

On the Influence of Group III/IV Muscle Afferent Feedback on Endurance Exercise Performance.

This review discusses evidence suggesting that group III/IV muscle afferents affect locomotor performance by influencing neuromuscular fatigue. These neurons regulate the hemodynamic and ventilatory response to exercise and, thus, assure appropriate locomotor muscle O2 delivery, which optimizes peripheral fatigue development and facilitates endurance performance. In terms of central fatigue, group III/IV muscle afferents inhibit motoneuronal output and thereby limit exercise performance.

Skeletal Muscle Mitochondrial Adaptations to Maximal Strength Training in Older Adults.

Maximal strength training (MST) results in robust improvements in skeletal muscle force production, efficiency, and mass. However, the effects of MST on muscle mitochondria are still unknown. Accordingly, the purpose of this study was to examine, from the molecular level to whole-muscle, mitochondrial adaptations induced by 8 weeks of knee-extension MST in the quadriceps of 10 older adults using immunoblotting, spectrophotometry, high-resolution respirometry in permeabilized muscle fibers, in vivo 31P magnetic resonance spectroscopy (31P-MRS), and gas exchange.

The exercise pressor reflex and chemoreflex interaction: cardiovascular implications for the exercising human.

Key Points: Although the exercise pressor reflex (EPR) and the chemoreflex (CR) are recognized for their sympathoexcitatory effect, the cardiovascular implication of their interaction remains elusive. We quantified the individual and interactive cardiovascular consequences of these reflexes during exercise and revealed various modes of interaction. The EPR and hypoxia-induced CR interaction is hyper-additive for blood pressure and heart rate (responses during co-activation of the two reflexes are greater than the summation of the responses evoked by each reflex) and hypo-additive for peripheral haemodynamics (responses during co-activation of the reflexes are smaller than the summated responses).

Calling Out MS Fatigue: Feasibility and Preliminary Effects of a Pilot Randomized Telephone-Delivered Exercise Intervention for Multiple Sclerosis Fatigue.

Background And Purpose: Fatigue is a common and debilitating symptom of multiple sclerosis (MS). Exercise therapy is effective in reducing MS-related fatigue; however, its feasibility, acceptability, and effectiveness when delivered over the telephone remain unknown. This randomized study aimed to determine the feasibility and acceptability of a telephone-delivered exercise intervention for MS-related fatigue.

Pharmacological attenuation of group III/IV muscle afferents improves endurance performance when oxygen delivery to locomotor muscles is preserved.

We sought to investigate the role of group III/IV muscle afferents in limiting endurance exercise performance, independently of their role in optimizing locomotor muscle O delivery. While breathing 100% O to ensure a similar arterial O content ([Formula: see text]) in both trials, eight male cyclists performed 5-km time trials under control conditions (H) and with lumbar intrathecal fentanyl (H) impairing neural feedback from the lower limbs. After each time trial, common femoral artery blood flow (FBF) was quantified (Doppler ultrasound) during constant-load cycling performed at the average power of the preceding time trial.

Impact of acute antioxidant administration on inflammation and vascular function in heart failure with preserved ejection fraction.

Although it is now well established that heart failure with preserved ejection fraction (HFpEF) is associated with marked inflammation and a prooxidant state that is accompanied by vascular dysfunction, whether acute antioxidant (AO) administration can effectively target these disease-related decrements has not been evaluated. Thus, the present study sought to evaluate the efficacy of an acute over-the-counter AO cocktail (600 mg α-lipoic acid, 1,000 mg vitamin C, and 600 IU vitamin E) to mitigate inflammation and oxidative stress, and subsequently improve nitric oxide (NO) bioavailability and vascular function, in patients with HFpEF. Flow-mediated dilation (FMD) and reactive hyperemia (RH) were evaluated to assess conduit vessel and microvascular function, respectively, 90 min after administration of either placebo (PL) or AO in 16 patients with HFpEF (73 ± 10 yr, EF 54-70%) using a double-blind, crossover design.

Non-combative taekwondo evokes highly anaerobic physiological responses in elite-level athletes: potential evidence for a new training modality.

Background: Despite the increasing international popularity of taekwondo (TKD) poomsae, there is a lack of physiological characterizations of elite-level competitors in the sport. Thus, the aim of the present study was to investigate the physiological demands associated with various types of TKD poomsae.

Methods: Eight male international TKD poomsae competitors carried out tae-geuk (TG) and professional (PF) poomsaes (in accordance with international competition standards), and consecutive TG (CTG) poomsae (a previously identified poomsae-specific training method).

Fatigue-related group III/IV muscle afferent feedback facilitates intracortical inhibition during locomotor exercise.

Key Points: This study investigated the influence of group III/IV muscle afferents on corticospinal excitability during cycling exercise and focused on GABA neuron-mediated inhibition as a potential underlying mechanism. The study provides novel evidence to demonstrate that group III/IV muscle afferent feedback facilitates inhibitory intracortical neurons during whole body exercise. Firing of these interneurons probably contributes to the development of central fatigue during physical activity.

Maximal strength training increases muscle force generating capacity and the anaerobic ATP synthesis flux without altering the cost of contraction in elderly.

Aging is associated with a progressive decline in skeletal muscle function, then leading to impaired exercise tolerance. Maximal strength training (MST) appears to be a practical and effective intervention to increase both exercise capacity and efficiency. However, the underlying physiological mechanisms responsible for these functional improvements are still unclear.

Impact of age on the development of fatigue during large and small muscle mass exercise.

To examine the impact of aging on neuromuscular fatigue following cycling (CYC; large active muscle mass) and single-leg knee-extension (KE; small active muscle mass) exercise, 8 young (25 ± 4 years) and older (72 ± 6 years) participants performed CYC and KE to task failure at a given relative intensity (80% of peak power output). The young also matched CYC and KE workload and duration of the old (iso-work comparison). Peripheral and central fatigue were quantified via pre-/postexercise decreases in quadriceps twitch torque (∆Q, electrical femoral nerve stimulation) and voluntary activation (∆VA).

Identifying the role of group III/IV muscle afferents in the carotid baroreflex control of mean arterial pressure and heart rate during exercise.

Key Points: We investigated the contribution of group III/IV muscle afferents to carotid baroreflex resetting during electrically evoked (no central command) and voluntary (requiring central command) isometric knee extension exercise. Lumbar intrathecal fentanyl was used to attenuate the central projection of μ-opioid receptor-sensitive group III/IV leg muscle afferent feedback. Spontaneous carotid baroreflex control was assessed by loading and unloading the carotid baroreceptors with a variable pressure neck chamber.

Implementation and outcomes of a pharmacy residency mentorship program.

Purpose: The implementation and outcomes of a pharmacy residency mentorship program are described.

Summary: The mentorship program at the Detroit Medical Center was formally implemented during the residency orientation period in 2013. Residents had up to two months after the start of the residency to choose a mentor, which we believed was an adequate amount of time to meet all members of the department of pharmacy.

Increasing relative humidity impacts low-intensity exercise in the heat.

Introduction: Many jobs require working or exercising at low intensities for extended periods in hot-humid climates; however, in these conditions the isolated effects of relative humidity (RH) remain unclear. Therefore, the purpose of this study was to examine how RH influenced thermoregulation and perception during low-intensity exercise in the heat.

Methods: There were 13 healthy men (age = 23 +/- 2 yr, mass = 83.

Epidemiology of severe influenza outcomes among adult patients with obesity in Detroit, Michigan, 2011.

We conducted a retrospective cohort study to evaluate the impact of obesity on influenza disease severity. Individuals with obesity were more likely to have lower pulmonary disease manifestations [OR=1·97 (95% CI 1·05, 3·69), P=0·03] and to be admitted to an inpatient ward [OR=2·93 (95% CI 1·50, 5·71), P=0·002] when compared with non-obese individuals. Among admitted individuals, persons with obesity were more likely to require a lengthy hospital stay [OR=3·86 (95% CI 1·03, 14·42), P=0·045].