Comparison of health benefits between a high intensity interval training and a moderate intensity continuous training when performed in a nonlaboratory setting, in moderately obese women

The objective of this pilot study was to compare the effects of a high-intensity interval training (HIIT) and a moderate intensity continuous training (MICT) performed within a fitness center, on various health indices of 49 sedentary and moderately obese women (age 37 ± 7 years; BMI 32 ± 4 kg/m2) randomly assigned to supervised exercise on a cycle ergometer, 3 times/week, during 12 weeks, at 60% (MICT, n=24) or 85% (HIIT, n=25) of their heart rate reserve for weeks 5-12. Anthropometry, body composition, cardiorespiratory fitness, CRF (2 km-walking test estimated V; O2max), quality of life, QoL (SF-36 Questionnaire), eating behaviors (Three Factor Eating Questionnaire, TFEQ) and perceived health (Short Health Perceived Questionnaire, SHPQ) were obtained before and after training from 10 HIIT vs. 13 MICT participants who completed the program. At baseline, both groups showed similar characteristics, except for a better sleep quality (SHPQ) in MICT than in HIIT participants (p<0.005). Increases in CRF (+3 to +5%) and decreases in body weight (-2%) and thus BMI (-2.5 to -4.5%), waist girth (-4%) and fat mass (-6 to - 8%) were comparable (0.0001<p<0.05). The physical component score (SF-36), the cognitive restriction and hunger scores (TFEQ), and the perceived health items (SPHQ) were similarly improved, irrespective of the training mode (0.01<p<0.05). Twelve weeks of either HIIT or MICT led to similar body weight and fat mass losses as well as to comparable improvements in CRF, QoL, eating behaviors and perceived health, in healthy, sedentary and moderately obese women. However, the large dropout in the HIIT (58%; 14 of 24) and MICT (48%; 12 of 25) groups questions the implementation of such training programs within a non-laboratory setting. Further studies are clearly needed to better adapt the conditions of practice to subjects' characteristics and thus promote their long-term adherence to exercise

Mitochondrial Dysregulation in the Pathogenesis of Diabetes: Potential for Mitochondrial Biogenesis-Mediated Interventions

Muscle mitochondrial metabolism is a tightly controlled process that involves the coordination of signaling pathways and factors from both the nuclear and mitochondrial genomes. Perhaps the most important pathway regulating metabolism in muscle is mitochondrial biogenesis. In response to physiological stimuli such as exercise, retrograde signaling pathways are activated that allow crosstalk between the nucleus and mitochondria, upregulating hundreds of genes and leading to higher mitochondrial content and increased oxidation of substrates. With type 2 diabetes, these processes can become dysregulated and the ability of the cell to respond to nutrient and energy fluctuations is diminished. This, coupled with reduced mitochondrial content and altered mitochondrial morphology, has been directly linked to the pathogenesis of this disease. In this paper, we will discuss our current understanding of mitochondrial dysregulation in skeletal muscle as it relates to type 2 diabetes, placing particular emphasis on the pathways of mitochondrial biogenesis and mitochondrial dynamics, and the therapeutic value of exercise and other interventions

Sex-Specific Impact of Ischemic Preconditioning on Tissue Oxygenation and Maximal Concentric Force

Prior peripheral hypoxia induced via remote ischemic preconditioning (IPC) can improve physical performance in male athletes through improved O2 delivery and utilization. Since females may have an innate protective mechanism against ischemia-reperfusion injury, and since muscle metabolism during contraction differs between sexes, it is relevant to examine the impact of sex in response to IPC to determine whether it is also ergogenic in females. In a randomized, crossover, single-blind study, we investigated muscle performance, hemodynamic and O2 uptake in strength-trained males (n = 9) and females (n = 8) performing five sets of 5 maximum voluntary knee extensions on an isokinetic dynamometer, preceded by either IPC (3 × 5-min ischemia/5-min reperfusion cycles at 200 mmHg) or SHAM (20 mmHg). Changes in deoxy-hemoglobin (Δ[HHb], expressed in percentage of arterial occlusion and considered an index of O2 extraction), and total hemoglobin (Δ[THb]) concentrations of the vastus lateralis muscle were continuously monitored by near-infrared spectroscopy. The metabolic efficiency of the contractions was calculated as the average force/Δ[HHb]avg ratio. Cohen's effect sizes (ES) ± 90% confidence limits were used to estimate IPC-induced changes and sex differences. IPC increased total muscular force in males only (13.0%, ES 0.64, 0.37;0.90), and this change was greater than in females (10.4% difference, ES 0.40, 0.10;0.70). Percent force decrement was only attenuated in females (−19.8%, ES −0.38, −0.77;0.01), which was clearly different than males (sex difference: ES 0.45, −0.16;1.07). IPC also induced different changes between sexes for average muscle O2 uptake in set 2 (males: 6.4% vs. females: −16.7%, ES 0.21, −0.18;0.60), set 3 (males: 7.0% vs. females: −44.4%, ES 0.56, −0.17;1.29), set 4 (males: 9.1% vs. females: −40.2%, ES 0.51, −0.10;1.13), and set 5 (males: 10.2% vs. females: −40.4%, ES 0.52, −0.04;1.09). However, metabolic efficiency was not meaningfully different between conditions and sexes. IPC increased muscle blood volume (↑[THb]) at rest and during recovery between sets, to the same extent in both sexes. Despite a similar IPC-induced initial increase in O2 delivery in both sexes, males displayed greater peripheral O2 extraction and greater strength enhancement. This ergogenic effect appears to be mediated in part via an up regulated oxidative function in males. We conclude that strength-trained males might benefit more from IPC than their female counterparts during repeated, maximal efforts

Ischemic preconditioning enhances aerobic adaptations to sprint-interval training in athletes without altering systemic hypoxic signaling and immune function

Optimizing traditional training methods to elicit greater adaptations is paramount for athletes. Ischemic preconditioning (IPC) can improve maximal exercise capacity and up-regulate signaling pathways involved in physiological training adaptations. However, data on the chronic use of IPC are scarce and its impact on high-intensity training is still unknown. We investigated the benefits of adding IPC to sprint-interval training (SIT) on performance and physiological adaptations of endurance athletes. In a randomized controlled trial, athletes included eight SIT sessions in their training routine for 4 weeks, preceded by IPC (3 × 5 min ischemia/5 min reperfusion cycles at 220 mmHg, n = 11) or a placebo (20 mmHg, n = 9). Athletes were tested pre-, mid-, and post-training on a 30 s Wingate test, 5-km time trial (TT), and maximal incremental step test. Arterial O2 saturation, heart rate, rate of perceived exertion, and quadriceps muscle oxygenation changes in total hemoglobin (Δ[THb]), deoxyhemoglobin (Δ[HHb]), and tissue saturation index (ΔTSI) were measured during exercise. Blood samples were taken pre- and post-training to determine blood markers of hypoxic response, lipid-lipoprotein profile, and immune function. Differences within and between groups were analyzed using Cohen's effect size (ES). Compared to PLA, IPC improved time to complete the TT (Mid vs. Post: −1.6%, Cohen's ES ± 90% confidence limits −0.24, −0.40;−0.07) and increased power output (Mid vs. Post: 4.0%, ES 0.20, 0.06;0.35), Δ[THb] (Mid vs. Post: 73.6%, ES 0.70, −0.15;1.54, Pre vs. Post: 68.5%, ES 0.69, −0.05;1.43), Δ[HHb] (Pre vs. Post: 12.7%, ES 0.24, −0.11;0.59) and heart rate (Pre vs. Post: 1.4%, ES 0.21, −0.13;0.55, Mid vs. Post: 1.6%, ES 0.25, −0.09;0.60). IPC also attenuated the fatigue index in the Wingate test (Mid vs. Post: −8.4%, ES −0.37, −0.79;0.05). VO2peak and maximal aerobic power remained unchanged in both groups. Changes in blood markers of the hypoxic response, vasodilation, and angiogenesis remained within the normal clinical range in both groups. We concluded that IPC combined with SIT induces greater adaptations in cycling endurance performance that may be related to muscle perfusion and metabolic changes. The absence of elevated markers of immune function suggests that chronic IPC is devoid of deleterious effects in athletes, and is thus a safe and potent ergogenic tool

Similar recovery of maximal cycling performance after ischemic preconditioning, neuromuscular electrical stimulation or active recovery in endurance athletes

This study investigated the efficacy of ischemic preconditioning (IPC) on the recovery of maximal aerobic performance and physiological responses compared with commonly used techniques. Nine endurance athletes performed two 5-km cycling time trials (TT) interspersed by 45 minutes of recovery that included either IPC, active recovery (AR) or neuromuscular electrical stimulation (NMES) in a randomized crossover design. Performance, blood markers, arterial O2 saturation (SpO2), heart rate (HR), near-infrared spectroscopy-derived muscle oxygenation parameters and perceptual measures were recorded throughout TTs and recovery. Differences were analyzed using repeated-measures ANOVAs and Cohen’s effect size (ES). The decrement in chronometric performance from TT1 to TT2 was similar between recovery modalities (IPC: -6.1 sec, AR: -7.9 sec, NMES: -5.4 sec, p = 0.84, ES 0.05). The modalities induced similar increases in blood volume before the start of TT2 (IPC: 13.3%, AR: 14.6%, NMES: 15.0%, p = 0.79, ES 0.06) and similar changes in lactate concentration and pH. There were negligible differences between conditions in bicarbonate concentration, base excess of blood and total concentration of carbon dioxide, and no difference in SpO2, HR and muscle O2 extraction during exercise (all p > 0.05). We interpreted these findings to suggest that IPC is as effective as AR and NMES to enhance muscle blood volume, metabolic by-products clearance and maximal endurance performance. IPC could therefore complement the athlete’s toolbox to promote recovery

Fatty acid content and enzymes of fatty acid metabolism in overwintering cold-hardy gall insects

Fatty acid content and enzymes of fatty acid metabolism were studied in overwintering larvae of two cold-hardy gall insects, the freeze-tolerant fly Eurosta solidaginis and the freeze-avoiding moth Epiblema scudderiana. Both species increased the proportion of unsaturated fatty acids during the winter. Whereas total lipid content did not change in Eurosta solidaginis, a decrease in total lipids over the winter in Epiblema scudderiana suggested the use of fat reserves to maintain basal metabolism. Changes in the activities of enzymes of fat oxidation correlated with these observations in Eurosta solidaginis: hydroxyacyl-CoA dehydrogenase, carnitine-palmitoyl transferase, and acetoacetyl-CoA thiolase activities all decreased during overwintering. In Epiblema scudderiana the same activities were constant, decreased, or increased. These activities were, however, higher in the fat-oxidizing, freeze-avoiding species than in the freeze-tolerant larvae. Lipid content in Epiblema scudderiana increased again by early spring, possibly indicating this pool as the fate of carbon derived from the spring clearance of the cryoprotectant glycerol pool. Decreased activities of malic enzyme and ATP-citrate lyase suggested decreased potential for fatty acid synthesis in both species over the winter, consistent with the cessation offeeding in the fall. The potential for ketone body metabolism, measured as the activity of P-hydroxybutyrate dehydrogenase, increased greatly in both species during overwintering; however, levels ofβ-hydroxybutyrate remained less than 0.35 μmol/g wet mass throughout the study period. These data indicate that changes to storage lipid profiles in order to maintain fluidity and to lipid-metabolizing enzyme activities may play important roles in insect cold hardiness

Ischemic preconditioning increases muscle perfusion, oxygen uptake and force in strength-trained athletes

Background: Muscle ischemia and reperfusion induced by ischemic preconditioning (IPC) can improve performance in various activities. However, underlying mechanisms are still poorly understood. Purpose: To examine the effects of IPC on muscle haemodynamics and O2 uptake during repeated maximal contractions. Methods: In a cross-over, randomized, single-blind study, ten strength-trained men performed five sets of 5 maximum voluntary knee extensions of the right leg on an isokinetic dynamometer, preceded by either IPC of the right lower limb (3x5-minutes compression/5-minutes reperfusion cycles at 200 mmHg) or SHAM (20 mmHg). Changes in deoxy-haemoglobin ([HHb]), expressed in percentage of arterial occlusion, and total haemoglobin ([THb]) concentrations of the vastus lateralis muscle were continuously monitored by near-infrared spectroscopy. Differences between IPC and SHAM were analyzed using Cohen’s effect sizes (ES) ± 90% confidence limits, and magnitude-based inferences. Results: Compared to SHAM, IPC likely increased muscle blood volume at rest (↑[THb], 46.5%, ES 0.56, 90% confidence limits for ES -0.21;1.32). During exercise, peak force was almost certainly higher (11.8%, ES 0.37, 0.27;0.47), average force was very likely higher (12.6%, ES 0.47, 0.29;0.66), and average muscle O2 uptake was possibly increased (15.8%, ES 0.36, -0.07;0.79) after IPC. In the recovery periods between contractions, IPC also increased blood volume after set one (23.6%, ES 0.30, -0.05;0.65) and five (25.1%, ES 0.32, 0.09;0.55). Conclusion: Three cycles of IPC immediately increased muscle perfusion and O2 uptake, conducive to higher repeated force capacity in strength-trained athletes. This manoeuvre therefore appears relevant to enhance exercise training stimulus.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

Oxidative damage and antioxidants in Rana sylvatica, the freeze-tolerant wood frog

Freeze-tolerant wood frogs (Rana sylvatica) must endure prolonged ischemia on freezing. Reperfusion on thawing brings with it the potential for oxidative damage due to reactive oxygen species formation, a well-known consequence of mammalian ischemia-reperfusion. To determine whether oxidative damage occurs during thawing and how frogs deal with this, we examined oxidative damage and antioxidant and prooxidant systems in tissues of Rana sylvatica and a nonfreezing relative, Rana pipiens. Glutathione status indicated little oxidative stress in tissues during freezing or thawing; an increase of the glutathione pool in the oxidized form was observed during freezing only in Rana sylvatica kidney (by 85%) and brain (by 33%). Oxidative damage to tissue lipids, measured as the levels of thiobarbituric acid- reactive substances and/or by an Fe(III)-xylenol orange assay, did not increase above control values over a freeze-thaw time course. Correlative data showing increased activities of some antioxidant enzymes during freezing, notably glutathione peroxidase (increasing 1.2- to 2.5-fold), as well as constitutively higher activities of antioxidant enzymes and higher levels of glutathione in the freeze-tolerant species compared with Rana pipiens, suggest that antioxidant defenses play a key role in amphibian freeze tolerance