Discrepancy between predicted and measured exercise intensity for eliciting the maximal rate of lipid oxidation.

Background And Aims: Ectopic lipid storage is implicated in type 2 diabetes pathogenesis; hence, exercise to deplete stores (i.e., at the intensity that allows for maximal rate of lipid oxidation; MLO) might be optimal for restoring metabolic health.

Whole body lipid oxidation during exercise is impaired with poor insulin sensitivity but not with obesity per se.

Equivocal findings regarding the influence of overweight/obesity on exercise lipid-oxidizing capacity (EX-LIPOX) might reflect inadequate control of ) acute energy balance/macronutrient composition of diet; ) intensity/duration of exercise; and/or ) insulin sensitivity (IS) of participant. To assess independent/combined influences of IS and overweight/obesity with other factors controlled, we recruited sedentary adults with normal weight (NW; = 15) or overweight/obesity (O; = 15) subdivided into metabolically healthy (MH; = 8) and unhealthy (MU; = 7) groups (IS; MH > MU). Participants completed a 9-day, weight-stabilizing, controlled-feeding protocol comprising measurements of resting metabolism, body composition, oral glucose tolerance, and maximal exercise capacity.

Oxygen uptake kinetics during exercise reveal central and peripheral limitation in patients with iliofemoral venous obstruction.

Objective: Pulmonary oxygen uptake (V˙O) kinetics measured during the initiation of exercise mirror energetic transition during daily activity. The aim of this study was to elucidate the pathophysiological mechanisms of exercise limitation of patients with chronic iliofemoral vein obstruction after deep vein thrombosis by measuring V˙O kinetics compared with patients with peripheral arterial disease (PAD) and healthy individuals.

Methods: Eleven patients with iliofemoral vein obstruction (7 men; age, 20-65 years), seven patients with PAD (all men; age 44-60 years) and eight healthy participants (5 men; age 28-58 years) were studied.

Energetics contribution during no-gi Brazilian jiu jitsu sparring and its association with regional body composition.

We used measurements of metabolic perturbation obtained after sparring to estimate energetics contribution during no-gi Brazilian jiu-jitsu. Ten advanced grapplers performed two six-minute sparring bouts separated by 24 hours. Kinetics of recovery rate of oxygen uptake was modelled and post-combat-sparring blood-lactate concentration measured to estimate oxygen equivalents for phospholytic and glycolytic components of anaerobic energetics, respectively.

The acute vs. chronic effect of exercise on insulin sensitivity: nothing lasts forever.

Regular exercise causes chronic adaptations in anatomy/physiology that provide first-line defense for disease prevention/treatment ('exercise is medicine'). However, transient changes in function that occur following each exercise bout (acute effect) are also important to consider. For example, in contrast to chronic adaptations, the effect of exercise on insulin sensitivity is predominantly rooted in a prolonged acute effect (PAE) that can last up to 72 h.

Feasibility of a progressive protocol of high-intensity interval training for overweight/obese, sedentary African American women: a retrospective analysis.

Background: African American (AA) women have a higher prevalence of obesity and related metabolic dysfunction and lower level of physical activity compared to white counterparts. Determining feasible exercise alternatives for AA women is, therefore, paramount. Time-efficient high-intensity interval training (HIIT) might be particularly suited for AA women who cite time constraints as a frequent barrier to exercise adherence.

Power training improves bone mineral density and fall risk for a postmenopausal woman with a history of osteoporosis and increased risk of falling: A case report.

The purpose of this case study was to assess the degree to which a 12-month power-based resistance-training program improved bone mineral density (BMD) and fall risk for a 70-year-old postmenopausal woman with osteoporosis and increased risk of falling. After an eight-week strength-development phase, we had the patient perform 44 weeks of resistance training with maximal force mobilization by instructing her to complete as many repetitions as possible during each 60-s set. We used dual-energy X-ray absorptiometry (DEXA) to assess BMD and Dynamic Gait Index (DGI) to assess fall risk before and after the intervention.

Severe-intensity constant-work-rate cycling indicates that ramp incremental cycling underestimates ⩒o2max in a heterogeneous cohort of sedentary individuals.

In the absence of a ⩒o2-work-rate plateau, debate continues regarding the best way to verify that the peak ⩒o2 achieved during incremental exercise (⩒o2peak) is the "true ⩒o2max." Oft-used "secondary criteria" have been questioned in conjunction with the contention that a severe-intensity constant-work-rate "verification bout" should be considered the "gold standard." The purpose of this study was to compare the ⩒o2peak during ramp incremental cycling (RAMP-INC) by a heterogeneous (with respect to body composition and sex) cohort of sedentary individuals with the ⩒o2peak during severe-intensity constant-work-rate cycling (CWR) performed after RAMP-INC at the highest work rate achieved.

High-intensity interval training accelerates oxygen uptake kinetics and improves exercise tolerance for individuals with cystic fibrosis.

Background: Exercise training provides benefits for individuals with cystic fibrosis; however, the optimal program is unclear. High-intensity interval training is safe and effective for improving 'functional capacity' in these individuals with peak rate of O uptake typically referenced. The ability to adjust submaximal rate of oxygen uptake (V̇O kinetics) might be more important for everyday function because maximal efforts are usually not undertaken.

No Influence of Overweight/Obesity on Exercise Lipid Oxidation: A Systematic Review.

Compared to lean counterparts, overweight/obese individuals rely less on lipid during fasting. This deficiency has been implicated in the association between overweight/obesity and blunted insulin signaling via elevated intramuscular triglycerides. However, the capacity for overweight/obese individuals to use lipid during exercise is unclear.

A Rapidly Incremented Tethered-Swimming Maximal Protocol for Cardiorespiratory Assessment of Swimmers.

Incremental exercise testing is the standard means of assessing cardiorespiratory capacity of endurance athletes. While the maximal rate of oxygen consumption is typically used as the criterion measurement in this regard, two metabolic breakpoints that reflect changes in the dynamics of lactate production/consumption as the work rate is increased are perhaps more relevant for endurance athletes from a functional standpoint. Exercise economy, which represents the rate of oxygen consumption relative to performance of submaximal work, is also an important parameter to measure for endurance-athlete assessment.

Exercise as 'precision medicine' for insulin resistance and its progression to type 2 diabetes: a research review.

Type 2 diabetes and obesity epidemics are in effect in the United States and the two pathologies are linked. In accordance with the growing appreciation that 'exercise is medicine,' it is intuitive to suggest that exercise can play an important role in the prevention and/or treatment of these conditions. However, if exercise is to truly be considered as a viable alternative to conventional healthcare prevention/treatment strategies involving pharmaceuticals, it must be prescribed with similar scrutiny.

Time-trial performance is not impaired in either competitive athletes or untrained individuals following a prolonged cognitive task.

It has been reported that mental fatigue decreases exercise performance during high-intensity constant-work-rate exercise (CWR) and self-paced time trials (TT) in recreationally-trained individuals. The purpose of this study was to determine whether performance is impaired following a prolonged cognitive task in individuals trained for competitive sport. Ten trained competitive athletes (ATH) and ten untrained healthy men (UNT) completed a 6-min severe-intensity CWR followed by a 6-min cycling TT immediately following cognitive tasks designed to either perturb (Stroop colour-word task and N-back task; PCT) or maintain a neutral (documentary watching; CON) mental state.

A Rapidly-Incremented Tethered-Swimming test for Defining Domain-Specific Training Zones.

The purpose of this study was to investigate whether a tethered-swimming incremental test comprising small increases in resistive force applied every 60 seconds could delineate the isocapnic region during rapidly-incremented exercise. Sixteen competitive swimmers (male, n = 11; female, n = 5) performed: (a) a test to determine highest force during 30 seconds of all-out tethered swimming (F) and the ΔF, which represented the difference between F and the force required to maintain body alignment (F), and (b) an incremental test beginning with 60 seconds of tethered swimming against a load that exceeded F by 30% of ΔF followed by increments of 5% of ΔF every 60 seconds. This incremental test was continued until the limit of tolerance with pulmonary gas exchange (rates of oxygen uptake and carbon dioxide production) and ventilatory (rate of minute ventilation) data collected breath by breath.

Improvement of Oxygen-Uptake Kinetics and Cycling Performance With Combined Prior Exercise and Fast Start.

Purpose: To investigate whether oxygen-uptake ([Formula: see text]) kinetics and simulated 4-km cycling performance are synergistically improved by prior "priming" exercise and an all-out starting strategy.

Methods: Nine men completed 4 target work trials (114 ± 17 kJ) to assess [Formula: see text] kinetics and cycling performance in a repeated-measures, crossover experimental design. Trials were initiated with either a 12-s all-out start or a self-selected start and preceded by prior severe-intensity (70%Δ) priming exercise or no priming exercise.

The mechanistic bases of the power-time relationship: muscle metabolic responses and relationships to muscle fibre type.

Key Points: The power-asymptote (critical power; CP) of the hyperbolic power-time relationship for high-intensity exercise defines a threshold between steady-state and non-steady-state exercise intensities and the curvature constant (W') indicates a fixed capacity for work >CP that is related to a loss of muscular efficiency. The present study reports novel evidence on the muscle metabolic underpinnings of CP and W' during whole-body exercise and their relationships to muscle fibre type. We show that the W' is not correlated with muscle fibre type distribution and that it represents an elevated energy contribution from both oxidative and glycolytic/glycogenolytic metabolism.

Effects of Priming and Pacing Strategy on Oxygen-Uptake Kinetics and Cycling Performance.

Purpose: To assess whether combining prior "priming" exercise with an all-out pacing strategy is more effective at improving oxygen-uptake (VO2) kinetics and cycling performance than either intervention administered independently.

Methods: Nine men completed target-work cycling performance trials using a self-paced or all-out pacing strategy with or without prior severe-intensity (70%Δ) priming exercise. Breath-by-breath pulmonary VO2 and cycling power output were measured during all trials.

High-intensity interval training without weight loss improves exercise but not basal or insulin-induced metabolism in overweight/obese African American women.

The purpose of this randomized controlled clinical trial was to determine the effect of a 14-week high-intensity interval training (HIIT) intervention with weight stability on metabolic flexibility, insulin sensitivity, and cardiorespiratory fitness in sedentary, premenopausal, nondiabetic, overweight/obese African American women. Twenty-eight subjects were allocated to one of two groups: HIIT, which performed three sessions per week of four high-intensity cycling intervals, or a control group (CON), which maintained their normal level of physical activity. Diet was controlled for all subjects to ensure weight stability.

Inorganic nitrate supplementation improves muscle oxygenation, O₂ uptake kinetics, and exercise tolerance at high but not low pedal rates.

We tested the hypothesis that inorganic nitrate (NO3 (-)) supplementation would improve muscle oxygenation, pulmonary oxygen uptake (V̇o2) kinetics, and exercise tolerance (Tlim) to a greater extent when cycling at high compared with low pedal rates. In a randomized, placebo-controlled cross-over study, seven subjects (mean ± SD, age 21 ± 2 yr, body mass 86 ± 10 kg) completed severe-intensity step cycle tests at pedal cadences of 35 rpm and 115 rpm during separate nine-day supplementation periods with NO3 (-)-rich beetroot juice (BR) (providing 8.4 mmol NO3 (-)/day) and placebo (PLA).

Effects of interval and continuous training on O2 uptake kinetics during severe-intensity exercise initiated from an elevated metabolic baseline.

The purpose of this study was to test the hypothesis that Vo2 kinetics would be speeded to a greater extent following repeated sprint training (RST), compared with continuous endurance training (ET), in the transition from moderate- to severe-intensity exercise. Twenty-three recreationally active subjects were randomly assigned to complete six sessions of ET (60-110 min of moderate-intensity cycling) or RST (four to seven 30-s all-out Wingate tests) over a 2-wk period. Subjects completed three identical work-to-work cycling exercise tests before and after the intervention period, consisting of baseline cycling at 20 W followed by sequential step increments to moderate- and severe-intensity work rates.

Muscle metabolic responses during high-intensity intermittent exercise measured by (31)P-MRS: relationship to the critical power concept.

We investigated the responses of intramuscular phosphate-linked metabolites and pH (as assessed by (31)P-MRS) during intermittent high-intensity exercise protocols performed with different recovery-interval durations. Following estimation of the parameters of the power-duration relationship, i.e.

Muscle metabolic determinants of exercise tolerance following exhaustion: relationship to the "critical power".

We tested the hypothesis that muscle high-energy phosphate compounds and metabolites related to the fatigue process would be recovered after exhaustion during recovery exercise performed below but not above critical power (CP) and that these changes would influence the capacity to continue exercise. Eight male subjects completed single-leg, knee-extension exercise to exhaustion (for ∼180 s) on three occasions, followed by a work-rate reduction to severe-intensity exercise, heavy-intensity exercise ( View Article and Find Full Text PDF

No effect of acute L-arginine supplementation on O₂ cost or exercise tolerance.

The extent to which dietary supplementation with the nitric oxide synthase (NOS) substrate, L-arginine (ARG), impacts on NO production and NO-mediated physiological responses is controversial. This randomised, double blinded, cross-over study investigated the effects of acute ARG supplementation on NO biomarkers, O₂ cost of exercise and exercise tolerance in humans. In one experiment, 15 subjects completed moderate- and severe-intensity running bouts after acute supplementation with 6 g ARG or placebo (PLA).

Effects of pacing strategy on work done above critical power during high-intensity exercise.

Purpose: We investigated the influence of pacing strategy on the work completed above critical power (CP) before exhaustion (W>CP) and the peak V˙O2 attained during high-intensity cycling.

Methods: After the determination of VO(2max) from a ramp incremental cycling (INC) test and the estimation of the parameters of the power-duration relationship for high-intensity exercise (i.e.