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1.
Artigo em Inglês | MEDLINE | ID: mdl-34855522

RESUMO

Simulated military operational stress (SMOS) provides a useful model to better understand resilience in humans as the stress associated with caloric restriction, sleep deficits, and fatiguing exertion degrades physical and cognitive performance. Habitual physical activity may confer resilience against these stressors by promoting favorable use-dependent neuroplasticity, but it is unclear how physical activity, resilience, and corticospinal excitability (CSE) relate during SMOS. PURPOSE: To examine associations between corticospinal excitability, physical activity, and physical performance during SMOS. METHODS: Fifty-three service members (age: 26±5yrs, 13 women) completed a five day and night intervention composed of familiarization, baseline, SMOS (two nights/days), and recovery days. During SMOS, participants performed rigorous physical and cognitive activities while receiving half of normal sleep (two 2h blocks) and caloric requirements. Lower and upper limb CSE were determined with transcranial magnetic stimulation (TMS) stimulus-response curves. Self-reported resilience, physical activity, military-specific physical performance (TMT) and endocrine factors were compared in individuals with high (HIGH) and low CSE based on a median split of lower limb CSE at baseline. RESULTS: HIGH had greater physical activity and better TMT performance throughout SMOS. Both groups maintained physical performance despite substantial psychophysiological stress. Physical activity, resilience, and TMT performance were directly associated with lower limb CSE. CONCLUSION: Individual differences in physical activity coincide with lower (but not upper) limb CSE. Such use-dependent corticospinal excitability directly relates to resilience and physical performance during SMOS. Future studies may use non-invasive neuromodulation to clarify the interplay among CSE, physical activity, and resilience and improve physical and cognitive performance.

2.
Artigo em Inglês | MEDLINE | ID: mdl-34568719

RESUMO

National guidelines recommend sentinel lymph node biopsy (SLNB) be offered to patients with > 10% likelihood of sentinel lymph node (SLN) positivity. On the other hand, guidelines do not recommend SLNB for patients with T1a tumors without high-risk features who have < 5% likelihood of a positive SLN. However, the decision to perform SLNB is less certain for patients with higher-risk T1 melanomas in which a positive node is expected 5%-10% of the time. We hypothesized that integrating clinicopathologic features with the 31-gene expression profile (31-GEP) score using advanced artificial intelligence techniques would provide more precise SLN risk prediction. METHODS: An integrated 31-GEP (i31-GEP) neural network algorithm incorporating clinicopathologic features with the continuous 31-GEP score was developed using a previously reported patient cohort (n = 1,398) and validated using an independent cohort (n = 1,674). RESULTS: Compared with other covariates in the i31-GEP, the continuous 31-GEP score had the largest likelihood ratio (G2 = 91.3, P < .001) for predicting SLN positivity. The i31-GEP demonstrated high concordance between predicted and observed SLN positivity rates (linear regression slope = 0.999). The i31-GEP increased the percentage of patients with T1-T4 tumors predicted to have < 5% SLN-positive likelihood from 8.5% to 27.7% with a negative predictive value of 98%. Importantly, for patients with T1 tumors originally classified with a likelihood of SLN positivity of 5%-10%, the i31-GEP reclassified 63% of cases as having < 5% or > 10% likelihood of positive SLN, for a more precise, personalized, and clinically actionable SLN-positive likelihood estimate. CONCLUSION: These data suggest the i31-GEP could reduce the number of SLNBs performed by identifying patients with likelihood under the 5% threshold for performance of SLNB and improve the yield of positive SLNBs by identifying patients more likely to have a positive SLNB.

3.
Eur J Sport Sci ; : 1-15, 2021 Aug 17.
Artigo em Inglês | MEDLINE | ID: mdl-34346851

RESUMO

Adaptation to military operational stress is a complex physiological response that calls upon the sympathetic nervous system (SNS), hypothalamic pituitary adrenal (HPA) axis and immune system, to create a delicate balance between anabolism and catabolism and meet the demands of an ever-changing environment. As such, resilience, the ability to withstand and overcome the negative impact of stress on military performance, is likely grounded in an appropriate biological adaptation to encountered stressors. Neuroendocrine [i.e. cortisol, epinephrine (EPI), norepinephrine (NE), neuropeptide-Y (NPY), and brain derived neurotropic factor (BDNF)], inflammatory [i.e. interleukin 6 (IL-6), IL-1ß, IL-4, IL-10 and tumour necrosis factor (TNF)-α], as well as growth and anabolic [i.e. insulin-like growth factor-I (IGF-I), testosterone, and dehydroepiandrosterone (DHEA)] biomarkers independently and interactively function in stress adaptations that are associated with a soldier's physical and psychological performance. In this narrative review, we detail biomarkers across neuroendocrine, inflammatory, and growth stimulating domains to better elucidate the biological basis of a resilient soldier. The findings from the reviewed studies indicate that military readiness and resiliency may be enhanced through better homeostatic control, better regulated inflammatory responses, and balanced anabolic/catabolic processes. It is unlikely that one class of biomarkers is better for assessing physiological resilience. Therefore, a biomarker panel that can account for appropriate balance across these domains may be superior in developing monitoring frameworks. Real-time physiological monitoring to assess biomarkers associated with resilience will be possible pending more sophisticated technologies and provide a field-expedient application for early identification and intervention of at-risk soldiers to improve military resiliency.

4.
Physiol Behav ; 236: 113413, 2021 07 01.
Artigo em Inglês | MEDLINE | ID: mdl-33811909

RESUMO

PURPOSE: To study the impact of 48 h of simulated military operational stress (SMOS) on executive function, in addition to the role of trait resilience (RES) and aerobic fitness (FIT) on executive function performance. Associations between executive function and neuropeptide-Y (NPY), brain-derived neurotropic factor (BDNF), insulin-like growth factor-I (IGF-I), oxytocin, and α-klotho (klotho) were assessed to elucidate potential biomarkers that may contribute to cognitive performance during a multi-factorial stress scenario. METHODS: Fifty-four service members (SM) (26.4 ± 5.4 years, 178.0 ± 6.5 cm, 85.2 ± 14.0 kg) completed the 5-day protocol, including daily physical exertion and 48 h of restricted sleep and caloric intake. Each morning subjects completed a fasted blood draw followed by Cognition, a 10-part cognitive test battery assessing executive function. SMs were grouped into tertiles [low (L-), moderate (M-), high (H-)] based on Connor Davidson Resilience Score (RES) and V˙O2peak (FIT). Repeated measures ANOVA were run to analyze the effect of day on cognitive performance and biomarker concentration. Separate two-way mixed ANOVAs were run to determine the interaction of group by day on cognitive function. Friedman test with Bonferroni-corrected pairwise comparisons were used if assumptions for ANOVA were not met. Associations between changes in biomarkers and cognitive performance were analyzed using parametric and non-parametric correlation coefficients. RESULTS: SMOS reduced SM vigilance -11.3% (p < 0.001) and working memory -5.6% (p = 0.015), and increased risk propensity +9.5% (p = 0.005). H-RES and H-FIT SMs demonstrated stable vigilance across SMOS (p > 0.05). Vigilance was compromised during SMOS in L- and M-RES (p = 0.007 and p = 0.001, respectively) as well as L- and M-FIT (p = 0.001 and p = 0.031, respectively). SMOS reduced circulating concentrations of α-klotho -7.2% (p = 0.004), NPY -6.4% (p = 0.001), and IGF-I -8.1% (p < 0.001) from baseline through the end of the protocol. BDNF declined -19.2% after the onset of sleep and caloric restriction (p = 0.005) with subsequent recovery within 48 h. Oxytocin remained stable (p > 0.05). Several modest associations between neuroendocrine biomarkers and cognitive performance were identified. CONCLUSION: This study demonstrates H-FIT and H-RES may buffer the impact of SMOS on vigilance. SMOS negatively impacted circulating neuroendocrine biomarkers. While BDNF returned to baseline concentrations by the end of the 5 d protocol, NPY, IGF-I, and α-klotho may require a longer recovery period. These data suggest that the military may benefit by training and/or selection processes targeting at augmenting trait resilience and aerobic fitness for increased readiness.


Assuntos
Função Executiva , Militares , Biomarcadores , Cognição , Exercício Físico , Humanos , Memória de Curto Prazo , Aptidão Física
6.
J Clin Aesthet Dermatol ; 14(9): E61-E63, 2021 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-34980974

RESUMO

Background: While patients with localized cutaneous melanoma (CM) generally have good five-year melanoma-specific survival rates, identifying patients with localized disease at a high risk of recurrence could allow them access to additional follow-up or surveillance. Objective: We sought to examine the prognostic value of the 31-gene expression profile (31-GEP) test for the risk of recurrence in stage I CM patients according to 31-GEP main class (low risk: Class 1 vs. high-risk: Class 2) and the lowest and highest risk 31-GEP subclasses (Class 1A vs. Class 2B). Methods: Data from a previously described meta-analysis detailing the 31-GEP results for patients with stage I CM (N = 623) were re-analyzed to determine 31-GEP accuracy. Results: Patients with stage I CM and a Class 1 31-GEP result were less likely to have a recurrence (15/556; 2.7% vs. 6/67; 9.0%; p=0.018) than patients with a Class 2 result and had a higher five-year recurrence-free survival (RFS) (96% vs. 85%). Patients with a Class 2 result were 2.8 times as likely to experience a recurrence (positive likelihood ratio: 2.82; 95% confidence interval: 1.38-5.77). In a subset of patients with stage I CM stratified further into 31-GEP subclasses (n = 206), patients with a Class 1A result had a higher five-year RFS than those with a Class 2B result (98% vs. 73%). Patients with a Class 2B result were also 6.5 times as likely to experience a recurrence (positive likelihood ratio: 6.45; 95% confidence interval: 2.44-17.00) than those with a Class 1A result, and the 31-GEP had a negative predictive value of 96.3% (95% confidence interval: 92.3%-98.4%). Conclusion: The 31-GEP test significantly differentiates between low and high recurrence risk in patients with stage I CM.

7.
Artigo em Inglês | MEDLINE | ID: mdl-32973684

RESUMO

Purpose: To determine if acute resistance exercise-induced increases in growth hormone (GH) and insulin-like growth factor-I (IGF-I) were differentially responsive for one or more molecular weight (MW) isoforms and if these responses were sex-dependent. Methods: College-aged men (n = 10) and women (n = 10) performed an acute resistance exercise test (ARET; 6 sets, 10 repetition maximum (10-RM) squat, 2-min inter-set rest). Serum aliquots from blood drawn Pre-, Mid-, and Post-ARET (0, +15, and +30-min post) were processed using High Performance Liquid Chromatography (HPLC) fractionation and pooled into 3 MW fractions (Fr.A: >60; Fr.B: 30-60; Fr.C: <30 kDa). Results: We observed a hierarchy of serum protein collected among GH fractions across all time points independent of sex (Fr.C > Fr.A > Fr.B, p ≤ 0.03). Sex × time interactions indicated that women experienced earlier and augmented increases in all serum GH MW isoform fraction pools (p < 0.05); however, men demonstrated delayed and sustained GH elevations (p < 0.01) in all fractions through +30-min of recovery. Similarly, we observed a sex-independent hierarchy among IGF-I MW fraction pools (Fr.A > Fr.B > Fr.C, p ≤ 0.01). Furthermore, we observed increases in IGF-I Fr. A (ternary complexes) in men only (p ≤ 0.05), and increases in Fr.C (free/unbound IGF-I) in women only (p ≤ 0.05) vs. baseline, respectively. Conclusions: These data indicate that the processing of GH and IGF-I isoforms from the somatotrophs and hepatocytes are differential in their response to strenuous resistance exercise and reflect both temporal and sex-related differences.


Assuntos
Hormônio do Crescimento Humano/sangue , Fator de Crescimento Insulin-Like I/metabolismo , Isoformas de Proteínas/sangue , Treinamento de Força , Adulto , Feminino , Humanos , Masculino , Fatores Sexuais , Adulto Jovem
8.
Behav Med ; 46(3-4): 290-301, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32787719

RESUMO

This research examines resilience from both cognitive and physiological perspectives and the relative importance of resilience for progression within an extremely physical training environment for 116 individuals. Our study provides a unique contribution as an examination of the combined effects of psychological and physiological resilience in the success of individuals in the first phase of a military special operations training course, the Navy's Basic Underwater Demolition/SEAL (BUD/S) course. Our study used the Connor-Davidson Resilience Scale (CD-RISC) for the psychological assessment and a blood sample to measure the concentrations of cortisol, DHEA and BDNF, each associated with stress adaptation and neuronal integrity. Our contributions include: heeding the call for more extensive research for resilience, examining physiological markers as predictors in training situations, combining psychological and physiological resilience into a single metric to assess resilience, and providing empirical support for the vital role of resilience in both stamina and persistence in training. Our findings indicate that both psychological and physiological resilience can be important predictors of persistence individually, but combining the measures provides a more holistic view to predict the success of an individual in this intensive training program. The present study has implications not only for the military community, but also for those individuals seeking elite performance in a broad array of fields, like professional athletes, CEO's, and emergency response workers.


Assuntos
Militares/psicologia , Resiliência Psicológica/ética , Adaptação Psicológica , Adulto , Fator Neurotrófico Derivado do Encéfalo/análise , Fator Neurotrófico Derivado do Encéfalo/sangue , Causalidade , Desidroepiandrosterona/análise , Desidroepiandrosterona/sangue , Análise Fatorial , Humanos , Hidrocortisona/análise , Hidrocortisona/sangue , Masculino , Prognóstico , Psicometria/métodos , Reprodutibilidade dos Testes , Inquéritos e Questionários
9.
J Strength Cond Res ; 2020 Jun 17.
Artigo em Inglês | MEDLINE | ID: mdl-32569125

RESUMO

Beckner, ME, Pihoker, AA, Darnell, ME, Beals, K, Lovalekar, M, Proessl, F, Flanagan, SD, Arciero, PJ, Nindl, BC, and Martin, BJ. Effects of multi-ingredient preworkout supplements on physical performance, cognitive performance, mood state, and hormone concentrations in recreationally active men and women. J Strength Cond Res XX(X): 000-000, 2020-Performance enhancement supplement research has primarily focused on the effectiveness of individual ingredients, rather than the combination. This study investigated the acute effects of 2 multi-ingredient preworkout supplements (MIPS), with beta-alanine and caffeine (BAC) and without (NBAC), compared with placebo (PLA) on anaerobic performance, endurance capacity, mood state, cognitive function, vascular function, and anabolic hormones. Thirty exercise-trained individuals (24.4 ± 4.9 years, 15 men and 15 women) completed a fatiguing exercise protocol on 3 separate occasions, 30 minutes after ingestion of BAC, NBAC, or PLA. Outcomes were analyzed using one-way or two-way repeated-measures analysis of variance, as appropriate (alpha = 0.05). Anaerobic power was greater when supplementing with NBAC (10.7 ± 1.2 W·kg) and BAC (10.8 ± 1.4 W·kg) compared with PLA (10.4 ± 1.2 W·kg) (p = 0.014 and p = 0.022, respectively). BAC improved V[Combining Dot Above]O2peak time to exhaustion (p = 0.006), accompanied by an increase in blood lactate accumulation (p < 0.001), compared with PLA. Both NBAC and BAC demonstrated improved brachial artery diameter after workout (p = 0.041 and p = 0.005, respectively), but PLA did not. L-arginine concentrations increased from baseline to postsupplement consumption of BAC (p = 0.017). Reaction time significantly decreased after exercise for all supplements. There was no effect of supplement on mood states. Exercise-trained individuals looking to achieve modest improvements in power and endurance may benefit from consuming MIPS before exercise.

10.
Artigo em Inglês | MEDLINE | ID: mdl-32547489

RESUMO

Microdialysis allows for a preview into local muscle metabolism and can provide physiological insight that blood measurements cannot. Purpose: To examine the potential differential IGF-I system regulation in interstitial fluid during unilateral stretch shortening cycle exercise. Methods: 10 men (26 ± 7 year) performed unilateral jumping [stretch shortening cycle (SSC) exercise at 50% of optimal jump height] until volitional fatigue on a sled apparatus. Biological sampling took place using a catheter inserted into an antecubital vein (serum), and 100 kDa microdialysis probes inserted into the thigh muscle of each exercise/control leg (dialysate). Serum was drawn before (Pre; -3 h) and after SSC [Post I (+0 h), II (+3 h), or III (+20 h)]; dialysate was sampled for 2 h before (Pre), during/immediately after (Ex), and 3 h into recovery (Rec) following SSC. IGF-I system parameters (free/total IGF-I and IGFBPs 1-6) were measured with immunoassays. Interstitial free IGF-I was estimated from dialysate IGF-I and relative recovery (ethanol) correction. Data were analyzed with repeated measures ANOVA. Results: Serum total IGF-I remained elevated +3 h (Post II: 182.8 ± 37.6 vs. Pre: 168.3 ± 35.0 ng/mL, p < 0.01), but returned to baseline by +20 h (Post III vs. Pre, p = 0.31). No changes in serum free IGF-I were noted. Serum BP-1 and -3 increased over baseline, but not until + 20 h after SSC (Post III vs. Pre: 7.6 ± 4.9 vs. 3.7 ± 2.3 and 1,048.6 ± 269.2 vs. 891.4 ± 171.2 ng/mL, respectively). We observed a decreased serum BP-6 +3 h after SSC (p < 0.01), followed by a return to baseline at +20 h (p = 0.64 vs. Pre). There were no exercise-induced changes in serum BP-2, -4, or -5. Unlike serum, there were no changes in dialysate or interstitial free IGF-I in either leg (p > 0.05). Dialysate BP-1 remained increased in both exercise and control legs through 3 h into recovery (Rec vs. Pre, p < 0.01). Dialysate BP-3 also demonstrated a prolonged elevation over Pre SSC concentrations, but in the exercise leg only (Ex and Rec vs. Pre, p < 0.04). We observed a prolonged decrease in dialysate BP-5 (Ex and Rec vs. Pre, p < 0.03) and an increase in BP-4 IP in the exercise leg only. There were no changes relative to Pre SSC in dialysate BP-2 or -6. Conclusions: Unilateral exercise drives differential regulation of the IGF-I system at both local and systemic levels. More specifically, this is the first study to demonstrate that localized exercise increases IGFBP-3, IGFBP-4 and decreases in IGFBP-5 in muscle interstitial fluid.


Assuntos
Proteínas de Ligação a Fator de Crescimento Semelhante a Insulina/metabolismo , Fator de Crescimento Insulin-Like I/metabolismo , Exercícios de Alongamento Muscular/fisiologia , Adulto , Humanos , Masculino , Microdiálise , Músculo Esquelético/metabolismo , Adulto Jovem
11.
Appl Physiol Nutr Metab ; 44(12): 1391-1394, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31618598

RESUMO

The legs of 9 men (age 21 ± 2 years, 45 ± 4 mL/(kg·min)) were randomly assigned to complete 6 sessions of high-intensity exercise training, involving either one or four 5-min bouts of counterweighted, single-leg cycling. Needle biopsies from vastus lateralis revealed that citrate synthase maximal activity increased after training in the 4-bout group (p = 0.035) but not the 1-bout group (p = 0.10), with a significant difference between groups post-training (13%, p = 0.021). Novelty Short-term training using brief intense exercise requires multiple bouts per session to increase mitochondrial content in human skeletal muscle.


Assuntos
Citrato (si)-Sintase/metabolismo , Exercício Físico , Músculo Quadríceps/enzimologia , Biópsia por Agulha , Humanos , Masculino , Mitocôndrias Musculares/metabolismo , Fatores de Tempo , Adulto Jovem
12.
Growth Horm IGF Res ; 42-43: 102-107, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-30399477

RESUMO

OBJECTIVE: To characterize the influence of mode (aerobic/resistance) and volume of exercise (moderate/high) on circulating GH immediately post-exercise as well as following the onset of sleep. DESIGN: This study used repeated measures in which subjects randomly completed 5 separate conditions: control (no exercise), moderate volume resistance exercise (MR), high-volume resistance exercise (HR), moderate volume aerobic exercise (MA), and high volume aerobic exercise (HA). METHODS: Subjects had two overnight stays on each of the 5 iterations. Serial blood draws began as soon as possible after the completion of the exercise session. Blood was obtained every 20 min for 24-h. GH was measured using a chemiluminescent immunoassay. Pooled samples representing post exercise (PE) and first nocturnal pulse (NP) were divided into two aliquots. One of these aliquots was chemically reduced by adding 10 mM glutathione (GSH) to break down disulfide-linked aggregates. RESULTS: No differences were observed when pooling GH response at post-exercise (2.02 ±â€¯0.21) and nocturnal pulse (2.63 ±â€¯0.51; p = .32). Pairwise comparisons revealed main effect differences between controls (1.19 ±â€¯0.29) and both MA (2.86 ±â€¯0.31; p = .009) and HA (3.73 ±â€¯0.71; p = .001). Both MA (p = .049) and HA (p = .035) responses were significantly larger than the MR stimulus (1.96 ±â€¯0.28). With GSH reduction, controls significantly differed from MA (p = .018) and HA (p = .003) during PE, but only differed from HA (p = .003) during NP. CONCLUSIONS: This study demonstrated similar GH responses to exercise and nocturnal pulse, indicating that mode and intensity of exercise does not proportionately affect GH dimeric isoform concentration.


Assuntos
Dissulfetos/metabolismo , Exercício Físico/fisiologia , Hormônio do Crescimento Humano/metabolismo , Força Muscular/fisiologia , Treinamento de Força , Sono/fisiologia , Dissulfetos/química , Hormônio do Crescimento Humano/química , Humanos , Isoformas de Proteínas
13.
Exp Physiol ; 102(3): 354-365, 2017 03 01.
Artigo em Inglês | MEDLINE | ID: mdl-28118678

RESUMO

NEW FINDINGS: What is the central question of this study? Are there sex-based differences in the acute skeletal muscle response to sprint interval training (SIT)? What is the main finding and its importance? In response to a SIT protocol that involved three 20 s bouts of 'all-out' cycling, the expression of multiple genes associated with mitochondrial biogenesis, metabolic control and structural remodelling was largely similar between men and women matched for fitness. Our findings cannot explain previous reports of sex-based differences in the adaptive response to SIT and suggest that the mechanistic basis for these differences remains to be elucidated. A few studies have reported sex-based differences in response to several weeks of sprint interval training (SIT). These findings may relate to sex-specific responses to an acute session of SIT. We tested the hypothesis that the acute skeletal muscle response to SIT differs between sexes. Sedentary but healthy men (n = 10) and women (n = 9) were matched for age (22 ± 3 versus 22 ± 3 years old) and cardiorespiratory fitness [45 ± 7 versus 43 ± 10 ml O2  (kg fat-free mass)-1  min-1 ], with women tested in the mid-follicular phase of their menstrual cycles. Subjects performed three 20 s 'all-out' cycling efforts against a resistance of 5% of body mass, interspersed with 2 min of recovery. Relative mean power outputs [7.6 ± 0.5 versus 7.5 ± 0.9 W (kg fat-free mass)-1 ] were similar between men and women (P > 0.05). Furthermore, there were no differences in the exercise-induced changes in mRNA expression of PGC-1α, PRC, PPARD, SIRT1, RIP140, HSL, HKII, PDK4, PDP1, FOXO3, MURF-1, Myf5, MyoD and VEGFA at 3 h of recovery versus rest (P < 0.05, main effect of time). The only sex-specific responses to exercise were an increase in the mRNA expression of GLUT4 and LPL in women only and Atrogin-1 in men only (P < 0.05). Women also had higher expression of HKII and lower expression of FOXO3 compared with men (P < 0.05, main effect of sex). We conclude that the acute skeletal muscle response to SIT is largely similar in young men and women. The mechanistic basis for sex-based differences in response to several weeks of SIT that has been previously reported remains to be elucidated.


Assuntos
Exercício Físico/fisiologia , Músculo Esquelético/metabolismo , Adulto , Feminino , Humanos , Masculino , Consumo de Oxigênio/fisiologia , Resistência Física/fisiologia , Caracteres Sexuais , Fatores de Transcrição , Adulto Jovem
14.
Med Sci Sports Exerc ; 49(2): 298-307, 2017 02.
Artigo em Inglês | MEDLINE | ID: mdl-28009784

RESUMO

PURPOSE: Sprint interval training (SIT) is a time-efficient strategy to improve cardiorespiratory fitness (CRF); however, most protocols have been studied in laboratory settings and require specialized equipment. We investigated the efficacy of brief intense stair climbing as a practical model of SIT to improve CRF. METHODS: Two separate studies, each consisting of an acute and chronic phase, were conducted in a total of 31 sedentary women (age = 24 ± 10 yr, body mass index = 23 ± 4 kg·m). RESULTS: The acute phase of study 1 established that the mean HR, blood [lactate], and RPE were similar when participants (n = 8) performed an SIT protocol that involved 3 × 20-s "all-out" efforts of either continuously ascending stairs or cycling. The chronic phase demonstrated that CRF, as determined by peak oxygen uptake (V˙O2peak), increased by 12% or ~1 MET (8.27 ± 1.05 to 9.25 ± 1.01 METs, P = 0.002) when participants (n = 12) performed the 3 × 20-s stair climbing protocol 3 d·wk for 6 wk. The acute phase of study 2 established that HR and RPE were similar when participants (n = 11) performed three different stair climbing protocols: the 3 × 20-s continuous ascent model used in study 1 and two 3 × 60-s models of ascending and descending either one or two flights of stairs (P > 0.05). The chronic phase demonstrated that V˙O2peak increased by 7% (8.91 ± 1.30 to 9.51 ± 1.52 METs, P = 0.01) when the same group of participants performed the one-flight 3 × 60-s protocol 3 d·wk for 6 wk. The Cederholm index determined from an oral glucose tolerance test was 57 ± 17 and 64 ± 21 mg·L·mmol·mU·min before and after training, respectively (P = 0.056). CONCLUSION: Brief, intense stair climbing is a practical, time-efficient strategy to improve CRF in previously untrained women.


Assuntos
Aptidão Cardiorrespiratória , Subida de Escada/fisiologia , Glicemia/metabolismo , Teste de Esforço , Feminino , Frequência Cardíaca , Humanos , Ácido Láctico/sangue , Consumo de Oxigênio , Percepção , Esforço Físico , Adulto Jovem
15.
J Physiol ; 595(9): 2955-2968, 2017 05 01.
Artigo em Inglês | MEDLINE | ID: mdl-27396440

RESUMO

KEY POINTS: A classic unresolved issue in human integrative physiology involves the role of exercise intensity, duration and volume in regulating skeletal muscle adaptations to training. We employed counterweighted single-leg cycling as a unique within-subject model to investigate the role of exercise intensity in promoting training-induced increases in skeletal muscle mitochondrial content. Six sessions of high-intensity interval training performed over 2 weeks elicited greater increases in citrate synthase maximal activity and mitochondrial respiration compared to moderate-intensity continuous training matched for total work and session duration. These data suggest that exercise intensity, and/or the pattern of contraction, is an important determinant of exercise-induced skeletal muscle remodelling in humans. ABSTRACT: We employed counterweighted single-leg cycling as a unique model to investigate the role of exercise intensity in human skeletal muscle remodelling. Ten young active men performed unilateral graded-exercise tests to measure single-leg V̇O2, peak and peak power (Wpeak ). Each leg was randomly assigned to complete six sessions of high-intensity interval training (HIIT) [4 × (5 min at 65% Wpeak and 2.5 min at 20% Wpeak )] or moderate-intensity continuous training (MICT) (30 min at 50% Wpeak ), which were performed 10 min apart on each day, in an alternating order. The work performed per session was matched for MICT (143 ± 8.4 kJ) and HIIT (144 ± 8.5 kJ, P > 0.05). Post-training, citrate synthase (CS) maximal activity (10.2 ± 0.8 vs. 8.4 ± 0.9 mmol kg protein-1  min-1 ) and mass-specific [pmol O2 •(s•mg wet weight)-1 ] oxidative phosphorylation capacities (complex I: 23.4 ± 3.2 vs. 17.1 ± 2.8; complexes I and II: 58.2 ± 7.5 vs. 42.2 ± 5.3) were greater in HIIT relative to MICT (interaction effects, P < 0.05); however, mitochondrial function [i.e. pmol O2 •(s•CS maximal activity)-1 ] measured under various conditions was unaffected by training (P > 0.05). In whole muscle, the protein content of COXIV (24%), NDUFA9 (11%) and mitofusin 2 (MFN2) (16%) increased similarly across groups (training effects, P < 0.05). Cytochrome c oxidase subunit IV (COXIV) and NADH:ubiquinone oxidoreductase subunit A9 (NDUFA9) were more abundant in type I than type II fibres (P < 0.05) but training did not increase the content of COXIV, NDUFA9 or MFN2 in either fibre type (P > 0.05). Single-leg V̇O2, peak was also unaffected by training (P > 0.05). In summary, single-leg cycling performed in an interval compared to a continuous manner elicited superior mitochondrial adaptations in human skeletal muscle despite equal total work.


Assuntos
Adaptação Fisiológica , Treinamento Intervalado de Alta Intensidade/métodos , Mitocôndrias Musculares/metabolismo , Músculo Esquelético/fisiologia , Transporte de Elétrons , Humanos , Perna (Membro)/fisiologia , Masculino , Músculo Esquelético/metabolismo , Fosforilação Oxidativa , Consumo de Oxigênio , Adulto Jovem
16.
J Appl Physiol (1985) ; 121(6): 1282-1289, 2016 12 01.
Artigo em Inglês | MEDLINE | ID: mdl-27763877

RESUMO

We reported that supplementation with green tea extract (GTE) lowered the glycemic response to an oral glucose load following exercise, but via an unknown mechanism (Martin BJ, MacInnis MJ, Gillen JB, Skelly LE, Gibala MJ. Appl Physiol Nutr Metab 41: 1057-1063, 2016. Here we examined the effect of supplementation with GTE on plasma glucose kinetics on ingestion of a glucose beverage during exercise recovery. Eleven healthy, sedentary men (21 ± 2 yr old; body mass index = 23 ± 4 kg/m2, peak O2 uptake = 38 ± 7 ml·kg-1·min-1; means ± SD) ingested GTE (350 mg) or placebo (PLA) thrice daily for 7 days in a double-blind, crossover design. In the fasted state, a primed constant infusion of [U-13C6]glucose was started, and 1 h later, subjects performed a graded exercise test (25 W/3 min) on a cycle ergometer. Immediately postexercise, subjects ingested a 75-g glucose beverage containing 2 g of [6,6-2H2]glucose, and blood samples were collected every 10 min for 3 h of recovery. The rate of carbohydrate oxidation was lower during exercise after GTE vs. PLA (1.26 ± 0.34 vs. 1.48 ± 0.51 g/min, P = 0.04). Glucose area under the curve (AUC) was not different between treatments after drink ingestion (GTE = 1,067 ± 133 vs. PLA = 1,052 ± 91 mM/180 min, P = 0.91). Insulin AUC was lower after GTE vs. PLA (5,673 ± 2,153 vs. 7,039 ± 2,588 µIU/180 min, P = 0.05), despite similar rates of glucose appearance (GTE = 0.42 ± 0.16 vs. PLA = 0.43 ± 0.13 g/min, P = 0.74) and disappearance (GTE = 0.43 ± 0.14 vs. PLA = 0.44 ± 0.14 g/min, P = 0.57). We conclude that short-term GTE supplementation did not affect glucose kinetics following ingestion of an oral glucose load postexercise; however, GTE was associated with attenuated insulinemia. These findings suggest GTE lowers the insulin required for a given glucose load during postexercise recovery, which warrants further mechanistic studies in humans.


Assuntos
Ingestão de Alimentos/fisiologia , Exercício Físico/fisiologia , Glucose/metabolismo , Extratos Vegetais/administração & dosagem , Chá/química , Adulto , Glicemia/metabolismo , Estudos Cross-Over , Suplementos Nutricionais , Método Duplo-Cego , Glucose/administração & dosagem , Humanos , Insulina/metabolismo , Masculino , Oxirredução , Adulto Jovem
17.
Appl Physiol Nutr Metab ; 41(10): 1057-1063, 2016 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-27690569

RESUMO

Green tea extract (GTE) ingestion improves glucose homeostasis in healthy and diabetic humans, but the interactive effect of GTE and exercise is unknown. The present study examined the effect of short-term GTE supplementation on the glycemic response to an oral glucose load at rest and following an acute bout of exercise, as well as substrate oxidation during exercise. Eleven sedentary, overweight men with fasting plasma glucose (FPG) ≥5.6 mmol·L-1 (age, 34 ± 13 years; body mass index = 32 ± 5 kg·m-2; FPG = 6.8 ± 1.0; mean ± SD) ingested GTE (3× per day, 1050 mg·day-1 total) or placebo (PLA) for 7 days in a double-blind, crossover design. The effects of a 75-g glucose drink were assessed on 4 occasions during both GTE and PLA treatments: On days 1 and 5 at rest, and again following an acute bout of exercise on days 3 and 8. The glycemic response was assessed via an indwelling continuous glucose monitor (CGM) and venous blood draws. At rest, 1-h CGM glucose area under the curve was not different (P > 0.05), but the postexercise response was lower after GTE versus PLA (330 ± 53 and 393 ± 65 mmol·L-1·min-1, main effect of treatment, P < 0.05). The 1-h postprandial peaks in venous blood glucose (8.6 ± 1.6 and 9.8 ± 2.2 mmol·L-1) and insulin (96 ± 59 and 124 ± 68 µIU·ml-1) were also lower postexercise with GTE versus PLA (time × treatment interactions, P < 0.05). In conclusion, short-term GTE supplementation did not affect postprandial glucose at rest; however, GTE was associated with an attenuated glycemic response following a postexercise oral glucose load. These data suggest that GTE might alter skeletal muscle glucose uptake in humans.

18.
PLoS One ; 11(4): e0154075, 2016.
Artigo em Inglês | MEDLINE | ID: mdl-27115137

RESUMO

AIMS: We investigated whether sprint interval training (SIT) was a time-efficient exercise strategy to improve insulin sensitivity and other indices of cardiometabolic health to the same extent as traditional moderate-intensity continuous training (MICT). SIT involved 1 minute of intense exercise within a 10-minute time commitment, whereas MICT involved 50 minutes of continuous exercise per session. METHODS: Sedentary men (27±8y; BMI = 26±6kg/m2) performed three weekly sessions of SIT (n = 9) or MICT (n = 10) for 12 weeks or served as non-training controls (n = 6). SIT involved 3x20-second 'all-out' cycle sprints (~500W) interspersed with 2 minutes of cycling at 50W, whereas MICT involved 45 minutes of continuous cycling at ~70% maximal heart rate (~110W). Both protocols involved a 2-minute warm-up and 3-minute cool-down at 50W. RESULTS: Peak oxygen uptake increased after training by 19% in both groups (SIT: 32±7 to 38±8; MICT: 34±6 to 40±8ml/kg/min; p<0.001 for both). Insulin sensitivity index (CSI), determined by intravenous glucose tolerance tests performed before and 72 hours after training, increased similarly after SIT (4.9±2.5 to 7.5±4.7, p = 0.002) and MICT (5.0±3.3 to 6.7±5.0 x 10-4 min-1 [µU/mL]-1, p = 0.013) (p<0.05). Skeletal muscle mitochondrial content also increased similarly after SIT and MICT, as primarily reflected by the maximal activity of citrate synthase (CS; P<0.001). The corresponding changes in the control group were small for VO2peak (p = 0.99), CSI (p = 0.63) and CS (p = 0.97). CONCLUSIONS: Twelve weeks of brief intense interval exercise improved indices of cardiometabolic health to the same extent as traditional endurance training in sedentary men, despite a five-fold lower exercise volume and time commitment.


Assuntos
Treinamento Intervalado de Alta Intensidade , Resistência à Insulina , Consumo de Oxigênio , Resistência Física , Adolescente , Adulto , Metabolismo Energético , Exercício Físico , Teste de Tolerância a Glucose , Humanos , Masculino , Músculo Esquelético/fisiologia , Adulto Jovem
19.
J Appl Physiol (1985) ; 119(11): 1303-12, 2015 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-26384407

RESUMO

We tested the hypothesis that ingestion of sodium bicarbonate (NaHCO3) prior to an acute session of high-intensity interval training (HIIT) would augment signaling cascades and gene expression linked to mitochondrial biogenesis in human skeletal muscle. On two occasions separated by ∼1 wk, nine men (mean ± SD: age 22 ± 2 yr, weight 78 ± 13 kg, V̇O(2 peak) 48 ± 8 ml·kg(-1)·min(-1)) performed 10 × 60-s cycling efforts at an intensity eliciting ∼90% of maximal heart rate (263 ± 40 W), interspersed with 60 s of recovery. In a double-blind, crossover manner, subjects ingested a total of 0.4 g/kg body weight NaHCO3 before exercise (BICARB) or an equimolar amount of a placebo, sodium chloride (PLAC). Venous blood bicarbonate and pH were elevated at all time points after ingestion (P < 0.05) in BICARB vs. PLAC. During exercise, muscle glycogen utilization (126 ± 47 vs. 53 ± 38 mmol/kg dry weight, P < 0.05) and blood lactate accumulation (12.8 ± 2.6 vs. 10.5 ± 2.8 mmol/liter, P < 0.05) were greater in BICARB vs. PLAC. The acute exercise-induced increase in the phosphorylation of acetyl-CoA carboxylase, a downstream marker of AMP-activated protein kinase activity, and p38 mitogen-activated protein kinase were similar between treatments (P > 0.05). However, the increase in PGC-1α mRNA expression after 3 h of recovery was higher in BICARB vs. PLAC (approximately sevenfold vs. fivefold compared with rest, P < 0.05). We conclude that NaHCO3 before HIIT alters the mRNA expression of this key regulatory protein associated with mitochondrial biogenesis. The elevated PGC-1α mRNA response provides a putative mechanism to explain the enhanced mitochondrial adaptation observed after chronic HIIT supplemented with NaHCO3 in rats.


Assuntos
Exercício Físico/fisiologia , RNA Mensageiro/biossíntese , Bicarbonato de Sódio/farmacologia , Fatores de Transcrição/biossíntese , Adulto , Bicarbonatos/sangue , Estudos Cross-Over , Método Duplo-Cego , Glicogênio/metabolismo , Frequência Cardíaca/fisiologia , Humanos , Masculino , Mitocôndrias Musculares/metabolismo , Músculo Esquelético/metabolismo , Coativador 1-alfa do Receptor gama Ativado por Proliferador de Peroxissomo , Fosforilação , Adulto Jovem , Proteínas Quinases p38 Ativadas por Mitógeno/biossíntese , Proteínas Quinases p38 Ativadas por Mitógeno/genética
20.
PLoS One ; 9(11): e111489, 2014.
Artigo em Inglês | MEDLINE | ID: mdl-25365337

RESUMO

We investigated whether a training protocol that involved 3 min of intense intermittent exercise per week--within a total training time commitment of 30 min including warm up and cool down--could increase skeletal muscle oxidative capacity and markers of health status. Overweight/obese but otherwise healthy men and women (n = 7 each; age = 29±9 y; BMI = 29.8±2.7 kg/m2) performed 18 training sessions over 6 wk on a cycle ergometer. Each session began with a 2 min warm-up at 50 W, followed by 3×20 s "all-out" sprints against 5.0% body mass (mean power output: ∼450-500 W) interspersed with 2 min of recovery at 50 W, followed by a 3 min cool-down at 50 W. Peak oxygen uptake increased by 12% after training (32.6±4.5 vs. 29.1±4.2 ml/kg/min) and resting mean arterial pressure decreased by 7% (78±10 vs. 83±10 mmHg), with no difference between groups (both p<0.01, main effects for time). Skeletal muscle biopsy samples obtained before and 72 h after training revealed increased maximal activity of citrate synthase and protein content of cytochrome oxidase 4 (p<0.01, main effect), while the maximal activity of ß-hydroxy acyl CoA dehydrogenase increased in men only (p<0.05). Continuous glucose monitoring measured under standard dietary conditions before and 48-72 h following training revealed lower 24 h average blood glucose concentration in men following training (5.4±0.6 vs. 5.9±0.5 mmol/L, p<0.05), but not women (5.5±0.4 vs. 5.5±0.6 mmol/L). This was associated with a greater increase in GLUT4 protein content in men compared to women (138% vs. 23%, p<0.05). Short-term interval training using a 10 min protocol that involved only 1 min of hard exercise, 3x/wk, stimulated physiological changes linked to improved health in overweight adults. Despite the small sample size, potential sex-specific adaptations were apparent that warrant further investigation.


Assuntos
Exercício Físico , Músculo Esquelético/metabolismo , Miocárdio/metabolismo , Consumo de Oxigênio , Adaptação Fisiológica , Adulto , Glicemia , Metabolismo Energético , Feminino , Indicadores Básicos de Saúde , Humanos , Masculino , Mitocôndrias/metabolismo , Obesidade/sangue , Obesidade/metabolismo , Sobrepeso/sangue , Sobrepeso/metabolismo , Fatores de Tempo , Adulto Jovem
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