RESUMEN
To evaluate if experiencing a short-term exposure (18-months) to factors such as menstrual irregularities, dieting, changes in exercise or body weight, and medication usage is associated with bone mineral density (BMD) in college-aged females. A retrospective survey assessing health behaviors during a recent 18-month time period and a DXA scan were completed in 641 females. A total of 45.5% of participants reported amenorrhea during the 18-month time period. Those who experienced amenorrhea had lower femoral neck BMD (p = 0.018), trochanter (p = 0.018) and spine BMD (p = 0.022) compared to eumenorrheic women. Lifetime oral contraceptive usage longer than six months was negatively associated with BMD at femoral neck (p = 0.018) and total hip (p = 0.021). Women who lost weight trended towards having the lowest BMD at all sites compared to women who gained weight. Following a very-low calorie diet during the time period was negatively correlated with spine BMD (p = 0.001). Time spent in vigorous and very vigorous activity was weakly correlated with some hip BMD sites but time spent in extremely vigorous activity was not. In conclusion, females who experienced weight loss, amenorrhea, or a very low-calorie diet within an 18-month period of time in young adulthood had lower BMD. Additionally, oral contraceptive usage for longer than six months during their lifetime was associated with lower BMD.
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Amenorrea , Densidad Ósea , Absorciometría de Fotón , Adulto , Anticonceptivos Orales/uso terapéutico , Femenino , Humanos , Menstruación , Estudios Retrospectivos , Adulto JovenRESUMEN
This study aimed to determine the prevalence of female athlete triad risk factors among female international volunteers based on the development and income status of their country of service. A total of 2164 past volunteers completed a retrospective survey. Countries' income and development statuses were coded using the respective annual United Nations World Economic Situations and Prospects reports. Independent t-tests, ANOVAs, and Pearson's Chi-Squared tests were used to assess group differences; corresponding odds ratios were calculated. Volunteers in nondeveloped (OR = 2.25, CI = 1.85-2.75) and non-high-income (OR = 2.17, CI = 1.75-2.70) countries had over twice the odds of experiencing secondary amenorrhea. More volunteers who served in nondeveloped countries reported an increase in exercise while serving (p = 0.005). Those who served in a nondeveloped (OR = 1.52, CI = 1.16-1.98) or non-high-income (OR = 1.45, CI = 1.08-1.94) country had higher odds of weight loss. However, volunteers serving in nondeveloped (OR = 0.52, CI = 0.44-0.63) and non-high-income (OR = 0.50, CI = 0.4-0.61) countries were less likely to report food insecurity compared to those in developed and high-income countries. Bone mineral density was within the expected range regardless of income and development status. Female volunteers who served in nondeveloped and non-high-income countries experienced higher odds of secondary amenorrhea, which was likely influenced by an increase in exercise and higher odds of weight loss.
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Amenorrea , Síndrome de la Tríada de la Atleta Femenina , Amenorrea/complicaciones , Países en Desarrollo , Femenino , Síndrome de la Tríada de la Atleta Femenina/complicaciones , Síndrome de la Tríada de la Atleta Femenina/epidemiología , Humanos , Renta , Masculino , Estudios Retrospectivos , Voluntarios , Pérdida de PesoRESUMEN
This study retrospectively compared the prevalence of factors related to the female athlete triad (low energy availability, secondary amenorrhea (SA), low bone mineral density (BMD)), and post-study BMD of female college students and female international volunteer missionaries (volunteers). Female college students (21-26 years) completed a survey that retrospectively assessed an 18-month study period (volunteer service or first 18 months of college); Diet History Questionnaire III (DHQ III) and Dual-Energy X-ray Absorptiometry (DXA) scan were optional. One-way ANOVAs and chi-squared distributions assessed group differences. Logistic regression assessed covariates of SA and BMD; corresponding odds ratios (OR) and confidence intervals (CI) were calculated. Statistical significance was set at p < 0.001. 3683 participants (58.8% volunteers, 31.5% non-volunteers, 9.8% others) provided complete survey data; 246 completed the DHQ III, and 640 had a post-study DXA scan. Volunteers had higher metabolic equivalent (MET) hours than non-volunteers and others (p < 0.001), and higher prevalence of food insecurity (p < 0.001) and SA (p < 0.001). Volunteers had higher odds of SA (OR = 2.17, CI = 1.75-2.62) than non-volunteers. Weight loss, body satisfaction, "other" weight loss methods, increased MET hours, and vomiting during the study period increased participants' odds of SA. Participants' average BMD Z-scores were within the expected range at all sites, with no significant group differences. Volunteers' higher MET hours and higher prevalence of food insecurity and SA did not result in significantly lower post-study period BMD.
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Síndrome de la Tríada de la Atleta Femenina , Absorciometría de Fotón , Densidad Ósea , Femenino , Síndrome de la Tríada de la Atleta Femenina/complicaciones , Humanos , Prevalencia , Estudios Retrospectivos , Factores de Riesgo , VoluntariosRESUMEN
Evidence suggests that male victims of intimate partner violence (IPV) are less likely to seek help for their victimization than female victims. Studies exploring barriers to help seeking are relatively scarce in the United Kingdom (UK) and those that have been undertaken across Europe, United States, Canada, and Australia have tended to rely on small samples of help-seeking men who have self-identified as victims of IPV. With a view to include more male victim voices in the literature, an anonymous qualitative questionnaire was distributed via social media. In total, 147 men (85% from the UK) who self-identified as being subject to abuse from their female partners, completed the questionnaire. The data was subjected to a deductive thematic analysis and one superordinate and two overarching themes were identified. The superordinate theme was stigmatized gender and the two overarching themes (subthemes in parentheses) were barriers prohibiting help seeking (status and credibility, health and well-being) and responses to initial help seeking (discreditation, exclusion/isolation, and helpfulness). The findings are discussed in the context of Overstreet and Quinn's (2013) interpersonal violence and stigma model and findings from previous research. The conclusions and recommendations promote education and training and advocate a radical change to policy.
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Víctimas de Crimen , Violencia de Pareja , Femenino , Humanos , Masculino , Hombres , Encuestas y Cuestionarios , Estados Unidos , ViolenciaRESUMEN
While running provides an accessible form of cardiovascular stimulus, many runners report lower extremity musculoskeletal injuries. Additionally, runners who develop overuse injuries, such as tibial stress fractures, also have higher loading rates (LR) and impact forces. PURPOSE: Therefore, the purpose of this study was to investigate how uphill treadmill running at iso-efficient speeds (IES; a speed-incline combination having the same metabolic intensity as level running) influences impact LR, and peak vertical ground reaction forces (GRF). METHODS: Eleven collegiate distance runners completed 3 experimental running conditions (0%, 4%, and 8% treadmill inclination). During each running condition, the metabolic intensity was controlled by implementing an IES for each runner. RESULTS: All variables of interest were significantly reduced as treadmill incline increased (0% > 4% > 8%). CONCLUSION: Incline running is more metabolically demanding compared to level running at the same speed. But, if speed is controlled to maintain metabolic output, runners could decrease LR and peak vertical GRF while achieving the same metabolic training stimulus as level running.
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Fracturas por Estrés , Traumatismos de la Pierna , Fenómenos Biomecánicos , Prueba de Esfuerzo , Humanos , TibiaRESUMEN
OBJECTIVE: We correlate and evaluate the accuracy of accepted anthropometric methods of percent body fat (%BF) quantification, namely, hydrostatic weighing (HW) and air displacement plethysmography (ADP), to 2 automatic adipose tissue quantification methods using computed tomography (CT). METHODS: Twenty volunteer subjects (14 men, 6 women) received head-to-toe CT scans. Hydrostatic weighing and ADP were obtained from 17 and 12 subjects, respectively. The CT data underwent conversion using 2 separate algorithms, namely, the Schneider method and the Beam method, to convert Hounsfield units to their respective tissue densities. The overall mass and %BF of both methods were compared with HW and ADP. RESULTS: When comparing ADP to CT data using the Schneider method and Beam method, correlations were r = 0.9806 and 0.9804, respectively. Paired t tests indicated there were no statistically significant biases. Additionally, observed average differences in %BF between ADP and the Schneider method and the Beam method were 0.38% and 0.77%, respectively. The %BF measured from ADP, the Schneider method, and the Beam method all had significantly higher mean differences when compared with HW (3.05%, 2.32%, and 1.94%, respectively). CONCLUSIONS: We have shown that total body mass correlates remarkably well with both the Schneider method and Beam method of mass quantification. Furthermore, %BF calculated with the Schneider method and Beam method CT algorithms correlates remarkably well with ADP. The application of these CT algorithms have utility in further research to accurately stratify risk factors with periorgan, visceral, and subcutaneous types of adipose tissue, and has the potential for significant clinical application.
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Tejido Adiposo/diagnóstico por imagen , Peso Corporal/fisiología , Tomografía Computarizada por Rayos X/métodos , Imagen de Cuerpo Entero/métodos , Adulto , Composición Corporal/fisiología , Femenino , Humanos , Masculino , Persona de Mediana Edad , Pletismografía/métodos , Reproducibilidad de los ResultadosRESUMEN
The aim of this investigation was to document the exercise program used by crewmembers (n = 9; 45 +/- 2 yr) while aboard the International Space Station (ISS) for 6 mo and examine its effectiveness for preserving calf muscle characteristics. Before and after spaceflight, we assessed calf muscle volume (MRI), static and dynamic calf muscle performance, and muscle fiber types (gastrocnemius and soleus). While on the ISS, crewmembers had access to a running treadmill, cycle ergometer, and resistance exercise device. The exercise regimen varied among the crewmembers with aerobic exercise performed approximately 5 h/wk at a moderate intensity and resistance exercise performed 3-6 days/wk incorporating multiple lower leg exercises. Calf muscle volume decreased (P < 0.05) 13 +/- 2% with greater (P < 0.05) atrophy of the soleus (-15 +/- 2%) compared with the gastrocnemius (-10 +/- 2%). Peak power was 32% lower (P < 0.05) after spaceflight. Force-velocity characteristics were reduced (P < 0.05) -20 to -29% across the velocity spectrum. There was a 12-17% shift in myosin heavy chain (MHC) phenotype of the gastrocnemius and soleus with a decrease (P < 0.05) in MHC I fibers and a redistribution among the faster phenotypes. These data show a reduction in calf muscle mass and performance along with a slow-to-fast fiber type transition in the gastrocnemius and soleus muscles, which are all qualities associated with unloading in humans. Future long-duration space missions should modify the current ISS exercise prescription and/or hardware to better preserve human skeletal muscle mass and function, thereby reducing the risk imposed to crewmembers.
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Ejercicio Físico/fisiología , Músculo Esquelético/fisiología , Vuelo Espacial , Adulto , Aerobiosis , Biopsia , Metabolismo Energético/fisiología , Femenino , Humanos , Contracción Isométrica/fisiología , Pierna/anatomía & histología , Pierna/fisiología , Imagen por Resonancia Magnética , Masculino , Persona de Mediana Edad , Contracción Muscular/fisiología , Fibras Musculares de Contracción Rápida/fisiología , Fibras Musculares de Contracción Lenta/fisiología , Músculo Esquelético/anatomía & histología , Músculo Esquelético/citología , Cadenas Pesadas de Miosina/metabolismo , Fenómenos Fisiológicos de la Nutrición , Aptitud Física/fisiología , IngravidezRESUMEN
The soleus muscle has been consistently shown to atrophy more than other leg muscles during unloading and is difficult to protect using various exercise countermeasure paradigms. However, the efficacy of aerobic exercise, a known stimulus for oxidative adaptations, has not been tested in combination with resistance exercise (RE), a known hypertrophic stimulus. We hypothesized that a concurrent exercise program (AE + RE) would preserve soleus fiber myosin heavy chain (MHC) I size and function during 60 days of bed rest. A secondary objective was to test the hypothesis that a leucine-enriched high protein diet would partially protect soleus single fiber characteristics. Soleus muscle biopsies were obtained before and after bed rest from a control (BR; n = 7), nutrition (BRN; n = 8), and exercise (BRE; n = 6) group. Single muscle fiber diameter (Dia), peak force (Po), contractile velocity, and power were studied. BR decreased (P < 0.05) MHC I Dia (-14%), Po (-38%), and power (-39%) with no change in contractile velocity. Changes in MHC I size (-13%) and contractile function (approximately 30%) from BRN were similar to BR. BRE decreased (P < 0.05) MHC I Dia (-13%) and Po (-23%), while contractile velocity increased (P < 0.05) 26% and maintained power. These soleus muscle data show 1) the AE + RE exercise program maintained MHC I power but not size and strength, and 2) the nutrition countermeasure did not benefit single fiber size and contractile function. The divergent response in size and functional MHC I soleus properties with the concurrent exercise program was a unique finding further highlighting the challenges of protecting the unloaded soleus.
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Reposo en Cama/efectos adversos , Ejercicio Físico/fisiología , Fibras Musculares Esqueléticas/fisiología , Músculo Esquelético/fisiología , Fenómenos Fisiológicos de la Nutrición/fisiología , Medidas contra la Ingravidez , Adulto , Femenino , Inclinación de Cabeza , Humanos , Contracción Muscular/fisiología , Fibras Musculares Esqueléticas/química , Fibras Musculares Esqueléticas/ultraestructura , Fuerza Muscular/fisiología , Músculo Esquelético/anatomía & histología , Músculo Esquelético/citología , Cadenas Pesadas de Miosina/metabolismo , Cadenas Ligeras de Miosina/metabolismoRESUMEN
There is limited information on skeletal muscle properties in women with unloading and countermeasure programs to protect the unloading-induced atrophy. The current investigation tested the hypothesis that a concurrent aerobic and resistance exercise training program would preserve size and contractile function of slow- and fast-twitch muscle fibers. A secondary objective was to test the hypothesis that a leucine-enriched high-protein diet would partially attenuate single fiber characteristics. Vastus lateralis muscle biopsies were obtained before and on day 59 of bed rest from a control (BR; n = 8), nutrition (BRN; n = 8), or exercise (BRE; n = 8) group. Single muscle fibers were studied for diameter, peak force (P(o)), contractile velocity, and power. Those in the BR group had a decrease (P < 0.05) in myosin heavy chain (MHC) I diameter (-14%), P(o) (-35%), and power (-42%) and MHC IIa diameter (-16%) and P(o) (-31%; P = 0.06) and an increase (P < 0.05) in MHC hybrid fibers. Changes in size and function of MHC I (-19 to -44%) and IIa (-21% to -30%) fibers and MHC distribution in BRN individuals were similar to results in the BR group. In BRE conditions, MHC I and IIa size and contractile function were preserved during bed rest. These data show that the concurrent exercise program preserved the myocellular profile of the vastus lateralis muscle during 60-day bed rest. To combat muscle atrophy and function with long-term unloading, the exercise prescription program used in this study should be considered as a viable training program for the upper leg muscles, whereas the nutritional intervention used cannot be recommended as a countermeasure for skeletal muscle.
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Reposo en Cama , Proteínas en la Dieta/administración & dosificación , Terapia por Ejercicio , Fibras Musculares de Contracción Rápida/fisiología , Fibras Musculares de Contracción Lenta/fisiología , Atrofia Muscular , Adulto , Biopsia , Ejercicio Físico/fisiología , Femenino , Humanos , Contracción Muscular , Fibras Musculares de Contracción Rápida/química , Fibras Musculares de Contracción Lenta/química , Atrofia Muscular/dietoterapia , Atrofia Muscular/prevención & control , Cadenas Pesadas de Miosina/análisis , Músculo Cuádriceps/química , Músculo Cuádriceps/fisiología , Vuelo EspacialRESUMEN
The purpose of this investigation was to characterize the effects of marathon training on single muscle fiber contractile function in a group of recreational runners. Muscle biopsies were obtained from the gastrocnemius muscle of seven individuals (22 +/- 1 yr, 177 +/- 3 cm, and 68 +/- 2 kg) before, after 13 wk of run training, and after 3 wk of taper. Slow-twitch myosin heavy chain [(MHC) I] and fast-twitch (MHC IIa) muscle fibers were analyzed for size, strength (P(o)), speed (V(o)), and power. The run training program led to the successful completion of a marathon (range 3 h 56 min to 5 h 35 min). Oxygen uptake during submaximal running and citrate synthase activity were improved (P < 0.05) with the training program. Muscle fiber size declined (P < 0.05) by approximately 20% in both fiber types after training. P(o) was maintained in both fiber types with training and increased (P < 0.05) by 18% in the MHC IIa fibers after taper. This resulted in >60% increase (P < 0.05) in force per cross-sectional area in both fiber types. Fiber V(o) increased (P < 0.05) by 28% in MHC I fibers with training and was unchanged in MHC IIa fibers. Peak power increased (P < 0.05) in MHC I and IIa fibers after training with a further increase (P < 0.05) in MHC IIa fiber power after taper. These data show that marathon training decreased slow-twitch and fast-twitch muscle fiber size but that it maintained or improved the functional profile of these fibers. A taper period before the marathon further improved the functional profile of the muscle, which was targeted to the fast-twitch muscle fibers.
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Tolerancia al Ejercicio/fisiología , Ejercicio Físico/fisiología , Contracción Muscular/fisiología , Fibras Musculares de Contracción Rápida/fisiología , Fibras Musculares de Contracción Lenta/fisiología , Músculo Esquelético/fisiología , Carrera/fisiología , Adaptación Fisiológica/fisiología , Adulto , Femenino , Humanos , Masculino , Fibras Musculares de Contracción Rápida/citología , Fibras Musculares de Contracción Lenta/citologíaRESUMEN
Two pathways that have been implicated for cellular growth and development in response to muscle contraction are the extracellular signal-regulated kinase (ERK1/2) and Akt signaling pathways. Although these pathways are readily stimulated after exercise, little is known about how nutritional status may affect stimulation of these pathways in response to resistance exercise in human skeletal muscle. To investigate this, experienced cyclists performed 30 repetitions of knee extension exercise at 70% of one repetition maximum after a low (2%) or high (77%) carbohydrate (LCHO or HCHO) diet, which resulted in low or high (approximately 174 or approximately 591 mmol/kg dry wt) preexercise muscle glycogen content. Muscle biopsies were taken from the vastus lateralis before, approximately 20 s after, and 10 min after exercise. ERK1/2 and p90 ribosomal S6 kinase phosphorylation increased (P < or = 0.05) 10 min after exercise, regardless of muscle glycogen availability. Akt phosphorylation was elevated (P < 0.05) 10 min after exercise in the HCHO trial but was unaffected after exercise in the LCHO trial. Mammalian target of rapamycin phosphorylation was similar to that of Akt during each trial; however, change or lack of change was not significant. In conclusion, the ERK1/2 pathway appears to be unaffected by muscle glycogen content. However, muscle glycogen availability appears to contribute to regulation of the Akt pathway, which may influence cellular growth and adaptation in response to resistance exercise in a low-glycogen state.
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Glucógeno/metabolismo , Proteína Quinasa 1 Activada por Mitógenos/metabolismo , Proteína Quinasa 3 Activada por Mitógenos/metabolismo , Contracción Muscular/fisiología , Músculo Esquelético/fisiología , Resistencia Física/fisiología , Proteínas Serina-Treonina Quinasas/metabolismo , Proteínas Proto-Oncogénicas/metabolismo , Transducción de Señal/fisiología , Adulto , Carbohidratos de la Dieta/metabolismo , Humanos , Articulación de la Rodilla/fisiología , Masculino , Proteínas Proto-Oncogénicas c-aktRESUMEN
The aim of this study was to examine the time course activation of select myogenic (MRF4, Myf5, MyoD, myogenin) and metabolic (CD36, CPT1, HKII, and PDK4) genes after an acute bout of resistance (RE) or run (Run) exercise. Six RE subjects [25 +/- 4 yr (mean +/- SD), 74 +/- 14 kg, 1.71 +/- 0.11 m] and six Run subjects (25 +/- 4 yr, 72 +/- 5 kg, 1.81 +/- 0.07 m, 63 +/- 8 ml.kg(-1).min(-1)) were studied. Eight muscle biopsies were taken from the vastus lateralis (RE) and gastrocnemius (Run) before, immediately after, and 1, 2, 4, 8, 12 and 24 h after exercise. RE increased mRNA of MRF4 (3.7- to 4.5-fold 2-4 h post), MyoD (5.8-fold 8 h post), myogenin (2.6- and 3.5-fold 8-12 h post), HKII (3.6- to 10.5-fold 2-12 h post), and PDK4 (14- to 26-fold 2-8 h post). There were no differences in Myf5, CD36, and CPT1 mRNA levels 0-24 h post-RE. Run increased mRNA of MyoD (5.0- to 8.0-fold), HKII (12- to 16-fold), and PDK4 (32- to 52-fold) at 8-12 h postexercise. There were no differences in MRF4, Myf5, myogenin, CD36 and CPT1 mRNA levels 0-24 h post-Run. These data indicate a myogenic and metabolic gene induction with RE and Run exercise. The timing of the gene induction is variable and generally peaks 4-8 h postexercise with all gene expression not significantly different from the preexercise levels by 24 h postexercise. These data provide basic information for the timing of human muscle biopsy samples for gene-expression studies involving exercise.
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Ejercicio Físico/fisiología , Proteínas Musculares/biosíntesis , Proteínas Musculares/genética , Músculo Esquelético/metabolismo , Adulto , Femenino , Regulación de la Expresión Génica/fisiología , Humanos , Masculino , ARN Mensajero/biosíntesis , ARN Mensajero/genética , Factores de Tiempo , Activación TranscripcionalRESUMEN
To test the effects of tyrosine ingestion with or without carbohydrate supplementation on endurance performance, nine competitive cyclists cycled at 70% peak oxygen uptake for 90 min under four different feeding conditions followed immediately by a time trial. At 30-min intervals, beginning 60 min before exercise, each subject consumed either 5 ml/kg body wt of water sweetened with aspartame [placebo (Pla)], polydextrose (70 g/l) (CHO), L-tyrosine (25 mg/kg body wt) (Tyr), or polydextrose (70 g/l) and L-tyrosine (25 mg/kg body wt) (CHO+Tyr). The experimental trials were given in random order and were carried out by using a counterbalanced double-blind design. No differences were found between treatments for oxygen uptake, heart rate, or rating of perceived exertion at any time during the 90-min ride. Plasma tyrosine rose significantly from 60 min before exercise to test termination (TT) in Tyr (means +/- SE) (480 +/- 26 micromol) and CHO+Tyr (463 +/- 34 micromol) and was significantly higher in these groups from 30 min before exercise to TT vs. CHO (90 +/- 3 micromol) and Pla (111 +/- 7 micromol) (P < 0.05). Plasma free tryptophan was higher after 90 min of exercise, 15 min into the endurance time trial, and at TT in Tyr (10.1 +/- 0.9, 10.4 +/- 0.8, and 12.0 +/- 0.9 micromol, respectively) and Pla (9.7 +/- 0.5, 10.0 +/- 0.3, and 11.7 +/- 0.5 micromol, respectively) vs. CHO (7.8 +/- 0.5, 8.6 +/- 0.5, and 9.3 +/- 0.6 micromol, respectively) and CHO+Tyr (7.8 +/- 0.5, 8.5 +/- 0.5, 9.4 +/- 0.5 micromol, respectively) (P < 0.05). The plasma tyrosine-to-free tryptophan ratio was significantly higher in Tyr and CHO+Tyr vs. CHO and Pla from 30 min before exercise to TT (P < 0.05). CHO (27.1 +/- 0.9 min) and CHO+Tyr (26.1 +/- 1.1 min) treatments resulted in a reduced time to complete the endurance time trial compared with Pla (34.4 +/- 2.9 min) and Tyr (32.6 +/- 3.0 min) (P < 0.05). These findings demonstrate that tyrosine ingestion did not enhance performance during a cycling time trial after 90 min of steady-state exercise.