Self-Paced Free-Running Wheel Mimics High-Intensity Interval Training Impact on Rats’ Functional, Physiological, Biochemical, and Morphological Features

Abstract

Free-running wheel (FRW) is an animal exercise model that relies on high-intensity interval moments interspersed with low-intensity or pauses apparently similar to those performed in high-intensity interval training (HIIT). Therefore, this study, conducted over a 12-weeks period, aimed to compare functional, thermographic, biochemical and morphological skeletal and cardiac muscle adaptations induced by FRW and HIIT. Twenty-four male Wistar rats were assigned into three groups: sedentary rats (SED), rats that voluntarily exercise in free wheels (FRW) and rats submitted to a daily HIIT. Functional tests revealed that compared to SED both FRW and HIIT increased the ability to perform maximal workload tests (MWT-cm/s) (45 ± 1 vs. 55 ± 2 and vs. 65 ± 2). Regarding thermographic assays, FRW and HIIT increased the ability to lose heat through the tail during MWT. Histochemical analyzes performed in tibialis anterior (TA) and soleus (SOL) muscles showed a general adaptation toward a more oxidative phenotype in both FRW and HIIT. Exercise increased the percentage of fast oxidative glycolytic (FOG) in medial fields of TA (29.7 ± 2.3 vs. 44.9 ± 4.4 and vs. 45.2 ± 5.3) and slow oxidative (SO) in SOL (73.4 ± 5.7 vs. 99.5 ± 0.5 and vs. 96.4 ± 1.2). HITT decreased fiber cross-sectional area (FCSA-μm 2 ) of SO (4350 ± 286.9 vs. 4893 ± 325 and vs. 3621 ± 237.3) in SOL. Fast glycolytic fibers were bigger across all the TA muscle in FRW and HIIT groups. The FCSA decrease in FOG fibers was accompanied by a circularity decrease of SO from SOL fibers (0.840 ± 0.005 vs. 0.783 ± 0.016 and vs. 0.788 ± 0.010), and a fiber and global field capillarization increase in both FRW and HIIT protocols. Moreover, FRW and HIIT animals exhibited increased cardiac mitochondrial respiratory control ratio with complex I-driven substrates (3.89 ± 0.14 vs. 5.20 ± 0.25 and vs. 5.42 ± 0.37). Data suggest that FRW induces significant functional, physiological, and biochemical adaptations similar to those obtained under an intermittent forced exercise regimen, such as HIIT.

Maternal high-fat high-sucrose diet and gestational exercise modulate hepatic fat accumulation and liver mitochondrial respiratory capacity in mothers and male offspring

“…This discrepancy in RCR values might be a consequence of different exercise protocols, as well as animal models and diets. Actually, in our model, we combined endurance training with the free-running wheel, which has been suggested to prompt rats' oxidative capacity [54].…”

Building‐up fit muscles for the future

“…Ultimately, the triggering of these signalling cascades induced by maternal exercise, via 'skeletal muscle-derived activation', promotes several valuable molecular, physiological and functional outcomes in the offspring, such as increased skeletal muscle insulin sensitivity with long-term positive consequences on glucose homeostasis, favourable skeletal muscle development and diminished level of several promoters' gene methylation that increases offspring's exercise volition and endurance capacity insulin sensitivity in the offspring SM. 9,13, 36,49,50 Regarding the different exercise models, although free-running wheel (FRW) has been associated with clear SM-related benefits in health animals, 51 the absence of intensity control may be one the reasons associated with the variability and distinct outcomes described in studies involving metabolic constrains.…”

“…Albeit there are discrepancies among these studies due to the use of different strains of mice 31,36 and rats, 12,49,50 and different durations and modalities 13,31,36 of ME, in general, data suggest that ME before and during pregnancy improves glucose tolerance and insulin sensitivity in the offspring SM 9,13,36,49,50 . Regarding the different exercise models, although free‐running wheel (FRW) has been associated with clear SM‐related benefits in health animals, 51 the absence of intensity control may be one the reasons associated with the variability and distinct outcomes described in studies involving metabolic constrains.…”

The adaptations induced by Estrogen Related Receptor alpha (ERRα) disruption and exercise training on healthy and diabetic rat’s liver

“…The test started at a speed of 15 cm/s, after 5 min the speed was increased to 30 cm/s and then stepped up 3 cm/s every 2 min until maximal workload was achieved. This MWT allowed achieving VO 2 max-related speed in order to set the different workloads for the training protocol (Beleza et al 2019). The animals which showed good adaptation ti treadmill running were selected and entered to the study.…”