Influence of acute dietary nitrate supplementation on oxygen delivery/consumption and critical impulse during maximal effort forearm exercise in males: a randomized crossover trial.

Beetroot juice supplementation (BRJ) should increase nitric oxide bioavailability under conditions of muscle deoxygenation and acidosis that are a normal consequence of the maximal effort exercise test used to identify forearm critical impulse. We hypothesized BRJ would improve oxygen delivery:demand matching and forearm critical impulse performance. Healthy males (20.8 ± 2.4 years) participated in a randomized crossover trial between October 2017 and May 2018 (Queen's University, Kingston, ON). Participants completed 10 min of rhythmic maximal effort forearm handgrip exercise 2.5 h post placebo (PL) vs. BRJ (9 completed PL/BRJ vs. 4 completed BRJ/PL) within a 2 week period. Data are presented as mean ± SD. There was a main effect of drink (PL > BRJ) for oxygen extraction (P = 0.033, ηp2 = 0.351) and oxygen consumption/force (P = 0.017, ηp2 = 0.417). There was a drink × time interaction (PL > BRJ) for oxygen consumption/force (P = 0.035, ηp2 = 0.216) between 75 and 360 s (1.25-6 min) from exercise onset. BRJ did not influence oxygen delivery (P = 0.953, ηp2 = 0.000), oxygen consumption (P = 0.064, ηp2 = 0.278), metabolites ((lactate) (P = 0.196, ηp2 = 0.135), pH (P = 0.759, ηp2 = 0.008)) or power-duration performance parameters (critical impulse (P = 0.379, d = 0.253), W' (P = 0.733, d = 0.097)). BRJ during all-out handgrip exercise does not influence oxygen delivery or exercise performance. Oxygen cost of contraction with BRJ is reduced as contraction impulse is declining during maximal effort exercise resulting in less oxygen extraction.

Influence of acute dietary nitrate supplementation on oxygen delivery/consumption and limit of tolerance during progressive forearm exercise in men: a randomized crossover trial.

Beetroot juice (BRJ) supplementation increases nitric oxide bioavailability with hypoxia and acidosis, characteristics of high-intensity exercise. We investigated whether BRJ improved forearm oxygen delivery:demand matching in an intensity-dependent manner. Healthy men (21 ± 2.5 years) participated in a randomized crossover trial between October 2017 and May 2018 (Queen's University, Kingston, ON, Canada). Participants completed a forearm incremental exercise test to limit of tolerance (IET-LOT) 2.5 h post placebo (PL) versus BRJ (2 completed PL/BRJ vs. 9 completed BRJ/PL) within a 2-week period. Data are presented as mean ± standard deviation. There was a significant main effect of drink (PL < BRJ; P = 0.042, ηp2 = 0.385) and drink × intensity interaction for arteriovenous oxygen difference (PL < BRJ; P = 0.03; ηp2= 0.197; 20%-50% and 90% LOT). BRJ did not influence oxygen delivery (P = 0.893, ηp2 = 0.002), forearm blood flow (P = 0.589, ηp2 = 0.03) (forearm vascular conductance (P = 0.262, ηp2 = 0.124), mean arterial pressure (P = 0.254,ηp2 = 0.128)), oxygen consumption (P = 0.194, ηp2 = 0.179) or LOT (P = 0.432, d = 0.247). In healthy men, BRJ did not improve forearm oxygen delivery (vasodilatory or pressor response) during IET-LOT. Increased arteriovenous oxygen difference at submaximal intensities did not significantly influence oxygen consumption or performance across the entire range of forearm exercise intensities. This study adds to the growing body of evidence that BRJ does not influence small muscle mass blood flow in humans regardless of exercise intensity.

Does a single bout maximal effort forearm exercise test for determining critical impulse result in maximal oxygen delivery and consumption in men? A randomized crossover trial.

In a single bout maximal effort isometric forearm handgrip exercise test (maximal effort exercise test, MXT), contraction impulse exhibits exponential decay to an asymptote equivalent to critical impulse (CI). It is unknown whether oxygen delivery (O2del) and consumption (V˙O2) achieved at CI are maximal. Healthy men participated in a randomized crossover trial at Queen's University (Kingston, ON) between October 2017-May 2018. Participants completed an MXT and forearm incremental exercise test to limit of tolerance (IET-LOT) (7 completed MXT followed by IET-LOT vs. 4 completed IET-LOT followed by MXT) within a 2 week period. Data are presented as mean ± standard deviation. Maximal forearm blood flow (FBF) and O2del were not different in 11 men (21 ± 2.5 years) between MXT and IET-LOT (FBF = 473.8 ± 132.2 mL/min vs. 502.3 ± 152.3 mL/min; P = 0.482, ηp2 = 0.015; O2del = 85.2 ± 23.5 mL/min vs. 92.2 ± 37.0 mL/min; P = 0.456, ηp2 = 0.012). However, MXT resulted in greater maximal V˙O2 than IET-LOT (44.5 ± 15.2 mL/min > 36.8 ± 11.4 mL/min; P = 0.007, ηp2 = 0.09), due to greater oxygen extraction (54.0 ± 10.0% > 44.4 ± 8.6%; P = 0.021, ηp2 = 0.185). As CI was 88.6 ± 8.2% of IET-LOT contraction impulse, maximal O2 cost of contractions in MXT was greater than IET-LOT (0.45 ± 0.14 mL/min/Ns > 0.33 ± 0.09 mL/min/Ns; P < 0.001, ηp2 = 0.166). In healthy men, MXT identifying CI results in similar peak oxygen delivery but greater peak V˙O2 via increased extraction compared to an IET-LOT, indicating increased oxygen cost. MXT-CI may better estimate maximal V˙O2 than traditional IET-LOT for this exercise modality.

Sleep Quality and Sleep Behaviors in Varsity Athletes: A Pilot Study.

Sleep hygiene practices may hinder university athletes from obtaining quality sleep to support health and performance. We sought to provide a comprehensive evaluation of sleep quality and behaviors in varsity athletes using validated sleep questionnaires: the Athlete Sleep Screening Questionnaire (ASSQ) and the Athlete Sleep Behavior Questionnaire (ASBQ). Sixty-four (n = 64) athletes participated (54% female; 71% Caucasian). The mean age was 20.3 ± 1.7 years and the mean BMI was 23.3 ± 3.3. Fifty-one percent met the threshold for adequate sleep (7+ h) and 54% reported being somewhat/very satisfied with sleep quality. Global scores for ASSQ Sleep Difficulty and ASBQ sleep behaviors were significantly correlated (r = 0.31; p = 0.014) and not significantly different across age, academic year, or residence. According to the ASSQ, 11% and 24% were classified as having severe or moderate sleep problems, respectively. The ASBQ categorized 62% as having "poor" sleep behaviors. Notable sleep-influencing factors included a high frequency of emotional/cognitive processing of sport-performance issues (46.9%), frequent use of light-emitting devices before bed (90%), training after 7 pm (65%), and the use of sleep medication (19%). Half of the university athletes did not meet the thresholds for adequate sleep, and some may require a referral for clinical sleep issues. The majority of these athletes' sleep behaviors do not promote adequate sleep. The ASSQ shows utility to assess gradations in clinical sleep difficulty; the ASBQ could be used in concert with the ASSQ to discern "cognitive and physiological arousal" targets for use in educational workshops designed to promote optimal sleep hygiene in university athletes.

Individual variation of follicular phase changes in endothelial function across two menstrual cycles.

NEW FINDINGS: What is the central question of this study? The purpose of this study was to determine intra-individual reproducibility of follicular phase changes in endothelial function (flow-mediated dilatation) over two menstrual cycles in healthy, premenopausal women. What is the main finding and its importance? Phase changes in endothelial function were not consistent at the individual level across two menstrual cycles, which challenges the utility of interpreting individual responses over one cycle. ABSTRACT: Evidence regarding the impact of menstrual phase on endothelial function is conflicting, and studies to date have examined responses only over a single cycle. It is unknown whether the observed inter-individual variability of phase changes in endothelial function reflects stable, inter-individual differences in responses to oestrogen (E2 ; a primary female sex hormone). The purpose of this study was to examine changes in endothelial function from the early follicular (EF; low-E2 ) phase to the late follicular (LF; high-E2 ) phase over two consecutive cycles. Fourteen healthy, regularly menstruating women [22 ± 3 years of age (mean ± SD)] participated in four visits (EFVisit 1 , LFVisit 2 , EFVisit 3 and LFVisit 4 ) over two cycles. Ovulation testing was used to determine the time between the LF visit and ovulation. During each visit, endothelial function [brachial artery flow-mediated dilatation (FMD)], E2 and progesterone were assessed. At the group level, there was no impact of phase or cycle on FMD (P = 0.48 and P = 0.65, respectively). The phase change in FMD in cycle 1 did not predict the phase change in cycle 2 (r = 0.03, P = 0.92). Using threshold-based classification (2 × typical error threshold), four of 14 participants (29%) exhibited directionally consistent phase changes in FMD across cycles. Oestrogen was not correlated between cycles, and this might have contributed to variability in the FMD response. The intra-individual variability in follicular fluctuation in FMD between menstrual cycles challenges the utility of interpreting individual responses to phase over a single menstrual cycle.

Integrating Exercise Counseling Into the Medical School Curriculum: A Workshop-Based Approach Using Behavior Change Techniques.

Objective. Physician physical activity (PA) counseling remains low due partly to lack of knowledge, emphasizing the importance of providing learning opportunities to develop competency, given the strong associations between PA and health. This study aimed to describe the behavior change techniques (BCTs) used in an "Exercise Expo" workshop and examine the workshop's effectiveness for improving social cognitions to discuss exercise with patients. Methods. Second-year medical students (N = 54; Mage ± SD = 25.4 ± 2.95 years) completed questionnaires assessing attitudes, perceived behavior control (PBC), subjective norms, and intentions to provide PA counseling pre- and postworkshop. Repeated-measures analyses of variance evaluated changes in these theory of planned behavior constructs. Results. The most used BCTs included presenting information from credible sources, with opportunities for practicing the behavior and receiving feedback. Significant increases in attitudes, PBC and intentions to discuss PA were observed from pre-post Exercise Expo (P ≤ .01). No statistically significant differences in subjective norms were observed (P = .06). Conclusions. The Exercise Expo significantly improved social cognitions for PA counseling among medical students. Future interventions should target improvements in subjective norms to increase the likelihood the workshop improves PA counseling behavior. The evidence supports the usefulness of a workshop-based educational strategy to enhance medical students' social cognitions for PA counseling.

No impact of acute hyperglycaemia on arterial stiffness in the early and late follicular phases of the menstrual cycle in young females.

NEW FINDINGS: • What is the central question of this study? This is the first study to examine the impact of acute hyperglycaemia on arterial stiffness across the early and late follicular phases of the menstrual cycle. • What is the main finding and its importance? Central and peripheral arterial stiffness were not impacted by acute hyperglycaemia. This indicates that premenopausal women might experience protection against deleterious effects of acute hyperglycaemia, regardless of menstrual cycle phase. This research furthers our understanding of the interaction between nutrient intake, hormonal fluctuation and vascular function in premenopausal women. ABSTRACT: Acute hyperglycaemia may result in transient increases in arterial stiffness. However, research in healthy premenopausal women is lacking, and the impact of menstrual phase [early follicular (EF; low oestrogen) and late follicular (LF; high oestrogen)] on vulnerability to acute hyperglycaemia-induced changes in arterial stiffness is unknown. We hypothesized that an acute hyperglycaemia-induced increase in arterial stiffness in the EF phase would be attenuated in the LF phase. Seventeen healthy, naturally menstruating women [21 ± 1 years of age (mean ± SD)] participated in three experimental visits. During two visits, in the EF and LF phase, arterial stiffness was assessed via central and peripheral (arm and leg) pulse wave velocity (PWV) before and 15, 45, 75 and 105 min after consuming an oral glucose challenge (75 g glucose in 300 ml of solution). Blood samples were taken to assess glucose, insulin, oestrogen and progesterone concentrations. During a third visit in the EF phase, participants ingested 300 ml of water as a time control for PWV. Despite significant increases in blood glucose and insulin (P < 0.001), both central and peripheral arm PWV remained unchanged across time and phase, indicating that neither acute hyperglycaemia nor menstrual phase had an impact on central or peripheral arm arterial stiffness. There was a small effect of phase for peripheral leg PWV, where PWV was lower in the LF phase (P = 0.04, Cohen's d = 0.39); however, and in contrast to recent results in young men, peripheral leg PWV was unaffected by hyperglycaemia. These results suggest that premenopausal women might experience protection from acute hyperglycaemia-induced increases in arterial stiffness.

The influence of acute hyperglycaemia on brachial artery flow-mediated dilatation in the early and late follicular phases of the menstrual cycle.

NEW FINDINGS: What is the central question of the study? This is the first study to examine the impact of acute hyperglycaemia on endothelial function [flow-mediated dilatation (FMD)] in premenopausal women across the early and late follicular (EF and LF) phases of the menstrual cycle. What is the main finding and its importance? Flow-mediated dilatation was impaired 90 min after glucose ingestion, with no significant difference between phases. This indicates that women are susceptible to acute hyperglycaemia-induced endothelial dysfunction in both the EF and LF phases of the menstrual cycle, despite potentially vasoprotective elevations in estradiol levels during the LF phase. ABSTRACT: Acute hyperglycaemia transiently impairs endothelial function in healthy men when assessed via flow-mediated dilatation (FMD). However, research in female participants is lacking, and the impact of menstrual phase [early follicular (EF) and late follicular (LF)] on vulnerability to acute hyperglycaemia-induced endothelial dysfunction is unknown. Seventeen healthy, naturally menstruating women [21 ± 1 years old (mean ± SD)] participated in three visits. During two visits (EFGlucose and LFGlucose ), brachial artery FMD was assessed before and 60, 90 and 120 min after an oral glucose challenge (75 g glucose). During an additional EF visit, participants ingested 300 ml of water (EFTimeControl ). Blood glucose and insulin increased 30 min after glucose ingestion (P < 0.001), with no difference between phases. Flow-mediated dilatation did not change in EFTimeControl (P = 0.748) but was reduced 90 min after glucose ingestion (Pre, 8.5 ± 2.5%; Post90, 6.6 ± 2.4%, P = 0.001; Cohen's d = 0.82), with no difference between phases (main effect of phase, P = 0.506; phase by time interaction, P = 0.391). To account for individual variability in the time course of the impact of hyperglycaemia, the maximal hyperglycaemia-induced impairment in FMD was determined in each participant and compared between phases, revealing no significant phase differences (EFGlucose , -3.1 ± 2.8%; LFGlucose , -2.4 ± 2.1%, P = 0.181; d = 0.34). These results indicate that, similar to findings in men, acute hyperglycaemia results in FMD impairment in young women. We did not detect significant protection from acute hyperglycaemia-induced endothelial dysfunction in the LF 'high-oestrogen' phase in this sample, and further research is needed to examine the potential for a protective effect of oestrogen exposure, including oral contraceptive pills and hormone replacement therapy.

Absence of compensatory vasodilation with perfusion pressure challenge in exercise: evidence for and implications of the noncompensator phenotype.

Compromising oxygen delivery (O2D) during exercise requires compensatory vasodilatory and/or pressor responses to protect O2D:demand matching. The purpose of the study was to determine whether compensatory vasodilation is absent in some healthy young individuals in the face of a sudden reduction in exercising forearm perfusion pressure and whether this affects the exercise pressor response. Twenty-one healthy young men (21.6 ± 2.0 yr) completed rhythmic forearm exercise at a work rate equivalent to 70% of their own maximal exercise vasodilation. During steady-state exercise, the exercising arm was rapidly adjusted from below to above heart level, resulting in a reduction in forearm perfusion pressure of -30.7 ± 0.9 mmHg. Forearm blood flow (ml/min; brachial artery Doppler and echo ultrasound), mean arterial blood pressure (mmHg; finger photoplethysmography), and exercising forearm venous effluent (antecubital vein catheter) measurements revealed distinct compensatory vasodilatory differences. Thirteen individuals responded with compensatory vasodilation (509 ± 128 vs. 632 ± 136 ml·min-1·100 mmHg-1; P < 0.001), while eight individuals did not (663 ± 165 vs. 667 ± 167 ml·min-1·100 mmHg-1; P = 0.6). Compensatory pressor responses between groups were not different (5.5 ± 5.5 and 9.7 ± 9.5 mmHg; P = 0.2). Forearm blood flow, O2D, and oxygen consumption were all protected in compensators (all P > 0.05) but not in noncompensators, who therefore suffered compromises to exercise performance (6 ± 14 vs. -36 ± 29 N; P = 0.004). Phenotypic differences were not explained by potassium or nitric oxide bioavailability. In conclusion, both compensator and noncompensator vasodilator phenotype responses to a sudden compromise to exercising muscle blood flow are evident. Interindividual differences in the mechanisms governing O2D:demand matching should be considered as factors influencing exercise tolerance. NEW & NOTEWORTHY In healthy young individuals, compromising submaximally exercising muscle perfusion appears to evoke compensatory vasodilation to defend oxygen delivery. Here we report the absence of compensatory vasodilation in 8 of 21 such individuals, despite their vasodilatory capacity and increases in perfusion with increasing exercise intensity being indistinguishable from compensators. The absence of compensation impaired exercise tolerance. These findings suggest that interindividual differences in oxygen delivery:demand matching efficacy affect exercise tolerance and depend on the nature of a delivery:demand matching challenge.

Dietary nitrate restores compensatory vasodilation and exercise capacity in response to a compromise in oxygen delivery in the noncompensator phenotype.

Recently, dietary nitrate supplementation has been shown to improve exercise capacity in healthy individuals through a potential nitrate-nitrite-nitric oxide pathway. Nitric oxide has been shown to play an important role in compensatory vasodilation during exercise under hypoperfusion. Previously, we established that certain individuals lack a vasodilation response when perfusion pressure reductions compromise exercising muscle blood flow. Whether this lack of compensatory vasodilation in healthy, young individuals can be restored with dietary nitrate supplementation is unknown. Six healthy (21 ± 2 yr), recreationally active men completed a rhythmic forearm exercise. During steady-state exercise, the exercising arm was rapidly transitioned from an uncompromised (below heart) to a compromised (above heart) position, resulting in a reduction in local pressure of -31 ± 1 mmHg. Exercise was completed following 5 days of nitrate-rich (70 ml, 0.4 g nitrate) and nitrate-depleted (70 ml, ~0 g nitrate) beetroot juice consumption. Forearm blood flow (in milliliters per minute; brachial artery Doppler and echo ultrasound), mean arterial blood pressure (in millimeters of mercury; finger photoplethysmography), exercising forearm venous effluent (ante-cubital vein catheter), and plasma nitrite concentrations (chemiluminescence) revealed two distinct vasodilatory responses: nitrate supplementation increased (plasma nitrite) compared with placebo (245 ± 60 vs. 39 ± 9 nmol/l; P < 0.001), and compensatory vasodilation was present following nitrate supplementation (568 ± 117 vs. 714 ± 139 ml ⋅ min-1 ⋅ 100 mmHg-1; P = 0.005) but not in placebo (687 ± 166 vs. 697 ± 171 min-1 ⋅ 100 mmHg-1; P = 0.42). As such, peak exercise capacity was reduced to a lesser degree (-4 ± 39 vs. -39 ± 27 N; P = 0.01). In conclusion, dietary nitrate supplementation during a perfusion pressure challenge is an effective means of restoring exercise capacity and enabling compensatory vasodilation.NEW & NOTEWORTHY Previously, we identified young, healthy persons who suffer compromised exercise tolerance when exercising muscle perfusion pressure is reduced as a result of a lack of compensatory vasodilation. The ability of nitrate supplementation to restore compensatory vasodilation in such noncompensators is unknown. We demonstrated that beetroot juice supplementation led to compensatory vasodilation and restored perfusion and exercise capacity. Elevated plasma nitrite is an effective intervention for correcting the absence of compensatory vasodilation in the noncompensator phenotype.

Metabolic demand and muscle activation during different forms of bodyweight supported locomotion in men with incomplete SCI.

Body weight supported locomotor training uses neuroplasticity principles to improve recovery following a spinal cord injury (SCI). Steady state locomotion using the same body weight support (BWS) percent was compared in 7 males (42.6 ± 4.29 years) with incomplete SCI and matched (gender, age) noninjured controls (42.7 ± 5.4 years) using the Lokomat, Manual Treadmill, and ZeroG. The VO2000, Polar Heart Rate (HR) Monitor, and lower limb electromyography (EMG) electrodes were worn during the 2-minute sessions. Oxygen uptake (VO2) and HR were expressed as percentage of peak values obtained using progressive arm ergometry; VO2 was also expressed relative to resting metabolic equivalents (METS). Filtered EMG signals from tibialis anterior (TA), rectus femoris (RF), biceps femoris (BF), and medial gastrocnemius (MG) were normalized to ZeroG stepping. The Lokomat required 30% of VO2 peak (2METS) compared to ~54% (3METS) for Manual Treadmill and ZeroG sessions. HR was 67% of peak during Lokomat sessions compared to ~83% for Manual Treadmill and ZeroG. Muscle activation was higher in treadmill conditions compared to the ZeroG primarily due to increased BF activity. At the same level of BWS, locomotion using the Manual Treadmill or the ZeroG is more aerobically demanding than the Lokomat. Treadmill modalities encourage greater hip extensor activation compared to overground locomotion.

Muscle activation during body weight-supported locomotion while using the ZeroG.

The ZeroG provides dynamic body weight support (BWS) using a harness while individuals with mobility impairments (e.g., spinal cord injury) ambulate overground. Muscle activity during locomotion using this device was studied in 13 nondisabled adults (age 23.8 +/- 2.7 yr). Electromyography (EMG) recordings were collected from tibialis anterior (TA), medial gastrocnemius (MG), rectus femoris (RF), and biceps femoris muscles during randomized walking trials at preferred speeds under five levels of BWS (0%, 20%, 40%, 60%, 80%). Filtered EMG signals from each trial were normalized to 0% BWS and correlated with gait phases. Muscle activity, averaged across muscles, decreased significantly at heel strike by 33.4% with increasing BWS. Offloading significantly decreased heel strike activity of RF (62.8%), MG (35.5%), and TA (25.9%). Gait cycle completion time increased with BWS primarily because of increased swing phase time. These results summarizing the effect of BWS on muscle activation during ambulation can now be compared with clinical populations using the ZeroG.

Effects of exercise training on fitness, mobility, fatigue, and health-related quality of life among adults with multiple sclerosis: a systematic review to inform guideline development.

OBJECTIVE: To conduct a systematic review of evidence surrounding the effects of exercise training on physical fitness, mobility, fatigue, and health-related quality of life in adults with multiple sclerosis (MS). DATA SOURCES: The databases included EMBASE, 1980 to 2011 (wk 12); Ovid MEDLINE and Ovid OLDMEDLINE, 1947 to March (wk 3) 2011; PsycINFO, 1967 to March (wk 4) 2011; CINAHL all-inclusive; SPORTDiscus all-inclusive; Cochrane Library all-inclusive; and Physiotherapy Evidence Database all-inclusive. STUDY SELECTION: The review was limited to English-language studies (published before December 2011) of people with MS that evaluated the effects of exercise training on outcomes of physical fitness, mobility, fatigue, and/or health-related quality of life. DATA EXTRACTION: One research assistant extracted data and rated study quality. A second research assistant verified the extraction and quality assessment. DATA SYNTHESIS: From the 4362 studies identified, 54 studies were included in the review. The extracted data were analyzed using a descriptive approach. There was strong evidence that exercise performed 2 times per week at a moderate intensity increases aerobic capacity and muscular strength. The evidence was not consistent regarding the effects of exercise training on other outcomes. CONCLUSIONS: Among those with mild to moderate disability from MS, there is sufficient evidence that exercise training is effective for improving both aerobic capacity and muscular strength. Exercise may improve mobility, fatigue, and health-related quality of life.