Effects of manipulating the duration and intensity of aerobic training sessions on the physical performance of rats

Abstract

This study investigated the effects of manipulating the load components of aerobic training sessions on the physical performance of rats. To achieve this purpose, adult male Wistar rats were divided into four groups: an untrained control (CON) group and training groups with a predominant overload in intensity (INT) or duration (DUR) or alternating and similar overloads in intensity and duration (ID). Prior to, during, and after 8 weeks of the control or training protocols, the performance of the rats (evaluated by their workload) was determined during fatiguing, incremental-speed treadmill running. Two additional incremental running tests were performed prior to and at the end of the protocols to measure the peak rate of oxygen consumption (VO2peak). As expected, the rats in the trained groups exhibited increased performance, whereas the untrained rats showed stable performance throughout the 8 weeks. Notably, the performance gain exhibited by the DUR rats reached a plateau after the 4th week. This plateau was not present in the INT or ID rats, which exhibited increased performance at the end of training protocol compared with the DUR rats. None of the training protocols changed the VO2peak values; however, these values were attained at faster speeds, which indicated increased running economy. In conclusion, our findings demonstrate that the training protocols improved the physical performance of rats, likely resulting from enhanced running economy. Furthermore, compared with overload in duration, overload in the intensity of training sessions was more effective at inducing performance improvements across the 8 weeks of the study.

Aerobic training induces differential expression of genes involved in lipid metabolism in skeletal muscle and white adipose tissues

“…In addition, the higher activity of citrate synthase observed in trained rats suggests improved FA oxidation in skeletal muscle in response to training. 39 Indeed, aerobic training protocols performed during similar periods (8 weeks) and at similar intensities (~60%-85% of maximum speed) increased the speed at which the maximum rate of oxygen consumption was attained and reduced the gross oxygen cost of running 33 ; altogether, these adaptations may explain the greater tolerance to aerobic exercise observed in our trained rats. Despite not influencing body weight gain, the 10-week training markedly reduced the weight of two adipose tissues evaluated (ie, EAT and RAT), thereby decreasing body adiposity.…”

“…The control rats were subjected to a slow walk on the treadmill for 5 minutes at a speed of 5 m.min ‒1 , once a day, 5 days a week during the 10‐week period. This control protocol was executed to expose all animals to the same stressful conditions (eg, handling and exposure to light electrical stimulation); a recent study using exercise sessions characterized by short‐duration, low‐intensity treadmill running as a control procedure did not show improvements in aerobic performance …”

Cardiorespiratory fitness predicts effective connectivity between the hippocampus and default mode network nodes in young adults

“…Converging evidence from animal and human studies can be challenging given that CRF is rarely measured in rodents (e.g., see Wisløff et al, ) and cellular‐level changes, such as adult hippocampal neurogenesis, cannot yet be directly measured in living humans. One parallel between these two bodies of literature is that CRF is increased through aerobic exercise training in both rodents (Avila, Kim, & Massett, ; Bedford et al, ; Lambert & Noakes, ; Teixeira‐Coelho et al, ) and humans (Hagberg et al, ; Kohrt et al, ). This may suggest that in rodents, greater CRF may be the underlying factor responsible for the relationship between aerobic exercise and adult hippocampal neurogenesis, hippocampal vasculature, and HC‐dependent memory task performance.…”

“…Studies that are cross‐sectional in nature but seek to test hypotheses regarding exposure to aerobic exercise use cardiorespiratory fitness (CRF) as the primary objective outcome of interest. CRF is increased through aerobic exercise training in both rodents (Bedford, Tipton, Wilson, Oppliger, & Gisolfi, ; Teixeira‐Coelho et al, ) and humans (Hagberg et al, ; Kohrt et al, ). CRF refers to an individual's ability to perform exercise integrating the respiratory, cardiovascular, and musculoskeletal systems for a prolonged period of time (American College of Sports Medicine, Thompson, Gordon, & Pescatello, ).…”

Rats with higher intrinsic exercise capacities exhibit greater preoptic dopamine levels and greater mechanical and thermoregulatory efficiencies while running

“…This phenomenon has been accepted as a protective mechanism that prevents the organism from achieving a physiological condition that would result in tissue damage (30). Depending on the environmental conditions (14,40) and some physical exercise features, e.g., intensity and duration (39,49), fatigue can be differentially influenced by alterations in multiple physiological responses that signal early exercise cessation, including hyperthermia (4,(31)(32)(33), degradation of energy substrates (17), and changes in the levels of neurotransmitters (7,8,13,53). Regarding the thermoregulatory influence on exercise fatigue, the increased heat production by the contracting muscles requires activation of heat loss mechanisms to maintain the core body temperature in a range compatible with physical performance and even life (51).…”