Effect of Menstrual Cycle Phase on Fuel Oxidation Post HIT in Women Reproductive Age: A Pilot Study.

Women of childbearing age have variations in substrate oxidation rates that can lead to overweight, type II diabetes, and other conditions that may be associated with metabolic inflexibility and the variations in estrogen concentrations observed during the monthly ovarian cycle. PURPOSE: This study aimed to verify and compare the influence of eight treadmill high-intensity interval training (HIT) sessions on carbohydrate and lipid oxidation rates (CHOox and LIPox, respectively) and intensities of ventilatory anaerobic thresholds (VATs) of women in different phases of the monthly ovarian cycle. METHODS: Eleven irregularly active women performed incremental treadmill exercise testing followed by submaximal work-rate running for 45 min to determine VATs, VO2peak, peak velocity (Vpeak), and substrate oxidation rates, before and after a training period, in different phases of their monthly ovarian cycle (follicular phase group, FL, n = 6; luteal phase group, LT, n = 5). The training period consisted of eight HIT sessions, composed each one of eight sets of 60 s running at 100%Vpeak interspersed by 75 s recovery every 48 h. RESULTS: Our results showed no significant differences in VATs intensities between groups. The comparison between groups showed significant differences in relative energy derived from CHO pre- and post-training of -61.42% and -59.26%, respectively, and LIP pre- and post-training of 27.46% and 34.41%, respectively. The relative energy derived from CHO after the training period was 18.89% and 25.50% higher for FL and LT, respectively; consequently, the relative energy derived from LIPox after the training period was 8,45% and 3.46% lower for FL and LT, respectively. Over the training period, Vpeak was ~13.5 km/h, which produced the relative intensities of ~89%VO2peak e ~93%HRpeak for both groups. CONCLUSION: The monthly ovarian cycle phases promote significant changes in substrate oxidation rates leading to a decrease in CHOox. High-intensity interval training can minimize the differences observed and constitute an alternative intervention.

Six HIT Sessions Improve Cardiorespiratory Fitness and Metabolic Flexibility in Insulin Resistant and Insulin Sensitive Adolescents with Obesity.

To evaluate the effect of high-intensity interval training (HIT) on the cardiorespiratory performance and substrate oxidation pattern in insulin-resistant and insulin-sensitive obese adolescents. METHODS: We recruited 25 obese adolescents in three schools, and trained them in six HIT sessions, comprising of six series at 100% and recovery at 50% peak velocity (Vpeak). For the evaluation, the participants were divided into two groups: insulin-resistant (IR, n = 12; HOMA index ≥3.16) and insulin-sensitive (IS, n = 13). All participants underwent cardiopulmonary and indirect calorimetry testing. We compared the effects of HIT before and after the intervention among the two groups. The data were analyzed using Student's t and Mann-Whitney (intergroup comparisons) and Student's t and Wilcoxon (pre- and post-training comparisons) tests; and Cohen's d (influence of HIT). RESULTS: There was a significant post-training increase in Vpeak, oxygen consumption (VO2), velocity (V), and heart rate (HR) at the exertion intensity at the first ventilatory anaerobic threshold (VAT1) in both groups (p < 0.05; d < 0.02). The exercise promoted changes in substrate oxidation rates of the groups, with an increase in carbohydrate oxidation (CHOox) for both IR (p = 0.064) and IS (p = 0.034). CONCLUSION: Six HIT sessions improved cardiorespiratory performance in both groups and increased CHOox in insulin-sensitive obese adolescents, suggesting its utility for increasing physical fitness and controlling glycemia in these population groups.

Six hit treadmill sessions improve lipid oxidation and ventilatory threshold intensities / Seis sessões de hit em esteira aumentam a oxidação de lipídios e limiares ventilatórios / Seis sesiones de hit en cinta de correr aumentan la oxidación de lípidos y umbrales ventilatorios

ABSTRACT Introduction: High-intensity interval training (HIT) has been used as an alternative to cardiorespiratory training performed continuously at submaximal intensity and over long periods. Objectives: Propose a treadmill HIT protocol and verify the influence of six HIT sessions with this protocol on ventilatory anaerobic thresholds (VATs) and substrate oxidation pattern during submaximal continuous exercise (SCE). Methods: Fifteen sporadically active subjects underwent maximal progressive testing before and after six HIT treadmill running sessions to determine peak oxygen uptake (VO2peak), peak velocity (Vpeak), and VATs followed by SCE to determine lipid (LIPox) and carbohydrate (CHOox) oxidation rates. The HIT sessions consisted of eight sets of 60s at 100%Vpeak, interspersed with 75s of passive recovery between sets and a 48h interval between sessions. Results: Our results showed increases in VAT intensities of 4.4% for VAT1 and 8.8% for VAT2, a decrease of 12.8% in CHOox and an increase of 23.7% for LIPox; accordingly, the relative energy derived from LIPox was 20.3% higher after the training period. Vpeak was ~15 km/h, producing intensities corresponding to ~84%VO2peak and ~91%FCpeak over the training period. Conclusion: The proposed protocol produced adaptations and intensities which are similar to those described in the literature, but unlike others, it can be applied in sporadically active individuals. Level of Evidence II; Comparative prospective study.

RESUMO Introdução: O treinamento cardiorrespiratório intervalado de alta intensidade (high-intensity interval training, HIT) tem sido utilizado como alternativa ao treinamento cardiorrespiratório contínuo de intensidade submáxima e duração prolongada. Objetivo: Propor um protocolo de HIT utilizando corrida em esteira e verificar a influência de seis sessões de HIT com esse protocolo sobre os limiares anaeróbios ventilatórios (LAVs) e o padrão de oxidação de substratos durante o exercício contínuo de intensidade submáxima (ECIS). Métodos: Quinze indivíduos irregularmente ativos foram submetidos, antes e após seis sessões de HIT com corrida em esteira, a teste progressivo máximo para determinação do pico de consumo de oxigênio (VO2pico), velocidade de pico (Vpico) e LAVs seguidos de ECIS para determinação das taxas de oxidação de lipídios (LIPox) e carboidratos (CHOox). As sessões de HIT eram compostas por oito séries de 60 segundos a 100%Vpico com 75 segundos de recuperação passiva entre as séries e com 48 horas de intervalo entre as sessões. Resultados: Observaram-se aumentos das intensidades de ocorrência dos LAVs (4,4% para LAV1 e 8,8% para LAV2), redução de 12,8% de CHOox e aumento de 23,7% de LIPox; como consequência, a energia relativa derivada de LIPox apresentou-se 20,3% maior após o período de treinamento. A Vpico foi de ~15 km/h, promovendo intensidades correspondentes a ~84%VO2pico e ~91%FCpico ao longo do período de treinamento. Conclusão: O protocolo proposto promoveu adaptações e intensidades similares às descritas na literatura; porém, ao contrário de outros, é passível de aplicação em indivíduos irregularmente ativos. Nível de Evidência II; Estudo prospectivo comparativo.

RESUMEN Introducción: El entrenamiento cardiorrespiratorio intermitente de alta intensidad (high-intensity interval training, HIT) ha sido utilizado como alternativa al entrenamiento cardiorrespiratorio continuo de intensidad submáxima y duración prolongada. Objetivo: Proponer un protocolo de HIT utilizando carrera en cinta y verificar la influencia de seis sesiones de HIT con ese protocolo sobre los umbrales anaeróbicos ventilatorios (UAVs) y el patrón de oxidación de substratos durante el ejercicio continuo de intensidad submáxima (ECIS). Métodos: Quince individuos irregularmente activos fueron sometidos, antes y después de seis sesiones de HIT con carrera en cinta, a test progresivo máximo para determinación del pico de consumo de oxígeno (VO2pico), velocidad de pico (Vpico) y UAVs seguidos de ECIS para determinación de las tasas de oxidación de lípidos (LIPox) y carbohidratos (CHOox). Las sesiones de HIT eran compuestas por ocho series de 60 segundos a 100%Vpico con 75 segundos de recuperación pasiva entre las series y con 48 horas de intervalo entre las sesiones. Resultados: Se observaron aumentos de las intensidades de ocurrencia de los UAVs (4,4% para UAV1 y 8,8% para UAV2), reducción de 12,8% de CHOox y aumento de 23,7% de LIPox; como consecuencia, la energía relativa derivada de LIPox se presentó 20,3% mayor después del período de entrenamiento. La Vpico fue de ~15 km/h, promoviendo intensidades correspondientes a ~84%VO2pico e ~91%FCpico a lo largo del período de entrenamiento. Conclusión: El protocolo propuesto promovió adaptaciones e intensidades similares a las descritas en la literatura; sin embargo, al contrario de otros, es pasible de aplicación en individuos irregularmente activos. Nivel de Evidencia II; Estudio prospectivo comparativo.