Effect of the order of concurrent training combined with resistance and high-intensity interval exercise on mTOR signaling and glycolytic metabolism in mouse skeletal muscle

Effects of the order of endurance and high-intensity interval exercise in combined training on mouse skeletal muscle metabolism

Endurance exercise (EE) mainly improves oxidative capacity, whereas high-intensity interval exercise (HIIE) also improves glycolytic capacity. There is growing evidence that suggests that combining EE with HIIE can lead to improved athletic performance and fitness outcomes compared with either form of exercise alone. This study aimed to elucidate whether the order in which EE and HIIE are performed in combined training affects oxidative metabolism and glycolysis in mouse skeletal muscle. Male ICR mice at 7 wk of age were divided into three groups: control (CON), EE-HIIE, and HIIE-EE. The total training period was 3 wk (3 times/week). Mice performed running on a treadmill as endurance exercise and swimming with a weight load of 10% of body weight as high-intensity interval exercise. EE before HIIE (EE-HIIE) improved running performance in the maximal EE capacity test (all-out test) and partly enhanced the expression levels of molecular signals involved in glycolysis compared with HIIE before EE (HIIE-EE). The order of exercise did not, however, impact the expression of proteins related to mitochondrial dynamics, including those involved in the morphological changes of mitochondria through repeated fusion and fission, as well as oxidative energy metabolism. The findings suggest that the order of exercise has no significant impact on the expression of proteins associated with glycolytic and oxidative energy metabolism. Nevertheless, our results indicate that the order of EE-HIIE may enhance running performance.

A Mango Leaf Extract (Zynamite®) Combined with Quercetin Has Exercise-Mimetic Properties in Human Skeletal Muscle

Zynamite PX^®, a mango leaf extract combined with quercetin, enhances exercise performance by unknown molecular mechanisms. Twenty-five volunteers were assigned to a control (17 males) or supplementation group (8 males, receiving 140 mg of Zynamite^® + 140 mg quercetin/8 h for 2 days). Then, they performed incremental exercise to exhaustion (IE) followed by occlusion of the circulation in one leg for 60 s. Afterwards, the cuff was released, and a 30 s sprint was performed, followed by 90 s circulatory occlusion (same leg). Vastus lateralis muscle biopsies were obtained at baseline, 20 s after IE (occluded leg) and 10 s after Wingate (occluded leg), and bilaterally at 90 s and 30 min post exercise. Compared to the controls, the Zynamite PX^® group showed increased basal protein expression of Thr²⁸⁷-CaMKIIδ_D (2-fold, p = 0.007) and Ser⁹-GSK3β (1.3-fold, p = 0.005) and a non-significant increase of total NRF2 (1.7-fold, p = 0.099) and Ser⁴⁰-NRF2 (1.2-fold, p = 0.061). In the controls, there was upregulation with exercise and recovery of total NRF2, catalase, glutathione reductase, and Thr²⁸⁷-CaMKIIδ_D (1.2-2.9-fold, all p < 0.05), which was not observed in the Zynamite PX^® group. In conclusion, Zynamite PX^® elicits muscle signaling changes in resting skeletal muscle resembling those described for exercise training and partly abrogates the stress kinases responses to exercise as observed in trained muscles.

Physiological profile comparison between high intensity functional training, endurance and power athletes

INTRODUCTION

High intensity functional trainings (HIFT), a recent development of high intensity trainings, includes in the same training session components of endurance exercises, elements of Olympic weightlifting and powerlifting, gymnastics, plyometrics and calisthenics exercises. Therefore, subjects practicing this type of activity are supposed to show physiological features that represent a combination of both endurance and power athletes. The aim of this study was to compare the physiological profile of three groups of age-matched endurance, HIFT and power athletes.

METHODS

A total of 30 participants, 18 to 38-year-old men were enrolled in the study. Participants were divided in three groups: HIFT (n = 10), endurance (END, n = 10), and power (POW, weightlifters, n = 10) athletes. All were evaluated for anthropometric characteristics, VO_2peak, handgrip, lower limb maximal isometric and isokinetic strength, countermovement vertical jump and anaerobic power through a shuttle run test on the field.

RESULTS

VO_2peak/kg was higher in END and HIFT than POW athletes (p = 0.001 and p = 0.007, respectively), but there were no significant differences between the first two. POW and HIFT athletes showed significant greater strength at the handgrip, countermovement jump and leg extension/flexion tests than END athletes. HIFT athletes showed highest results at the dynamic isokinetic test, while there were no significant differences at the shuttle run test among groups.

CONCLUSIONS

As HIFT reach aerobic levels similar to END athletes and power and strength output similar to POW athletes, it appears that HIFT programs are effective to improve both endurance-related and power-related physical fitness components.

Effect of lactate administration on mouse skeletal muscle under calorie restriction

Calorie restriction (CR) involves a reductions of calorie intake without altering the nutritional balance, and has many beneficial effects, such as improving oxidative metabolism and extending lifespan. However, CR decreases in skeletal muscle mass and fat mass in correlation with the reduction in food intake. Lactate is known to have potential as a signaling molecule rather than a metabolite during exercise. In this study, we examined the effects of the combination of caloric restriction and lactate administration on skeletal muscle adaptation in order to elucidate a novel role of lactate. We first demonstrated that daily lactate administration (equivalent to 1 g/kg of body weight) for 2 weeks suppressed CR-induced muscle atrophy by activating mammalian/mechanistic target of rapamycin (mTOR) signaling, a muscle protein synthesis pathway, and inhibited autophagy-induced muscle degradation. Next, we found that lactate administration under calorie restriction enhanced mitochondrial enzyme activity (citrate synthase and succinate dehydrogenase) and the expression of oxidative phosphorylation (OXPHOS) protein expression. Our results suggest that lactate administration under caloric restriction not only suppresses muscle atrophy but also improves mitochondrial function.