The aim of this study was to compare the effects of 3 sets of isometric conditioning activity (ICA), each with an equal total duration (9 s per set) but with different distributions contractions, on force production during ICA and subsequent countermovement jump (CMJ) performance. Fifteen resistance-trained males participated in this study (age: 22.1 ± 2.4 years; body mass: 85.1 ± 9.7 kg; height: 181.3 ± 6.5 cm; relative one-repetition maximum (1RM) in back squat: 1.59 ± 0.32 kg/kg of body mass). Participants completed 3 conditions, each consisting of ICA in the half-back squat with a pushing isometric muscle action (PIMA) position at a 120-degree knee angle against an immovable barbell, differing in repetition distribution: 3 sets of 9 repetitions lasting 1 s each (SUST-1), 3 sets of 3 repetitions lasting 3 s each (SUST-3), 3 sets of single repetitions lasting 9 s (SUST-9), and a control condition (CTRL) without ICA. A 1-minute rest was allowed between sets. Approximately 3 min pre-ICA and at 15 s, 3-, 6-, 9-, and 12-minutes post-ICA, the CMJ performance was assessed. Moreover, peak force (PF) production, and force generated at 100 (Force100) and 200 ms (Force200) during each ICA were evaluated. A two-way repeated measures ANOVA indicated a main effect of time on CMJ height (F = 2.674; p = 0.029; ηp2=0.171) but did not show significant differences between conditions (F = 0.934; p = 0.434; ηp2=0.067) or interactions (F = 0.826; p = 0.648; ηp2=0.060). Post-hoc comparisons indicated a significant decrease in CMJ height at the 9th minute compared to the 3rd minute (35.7 ± 5.6 cm vs. 36.8 ± 5.5 cm post-CA; d = 0.161; p = 0.048). In addition, no significant interactions or main effects were found for CMJ contraction time, PF and Force100 during ICA. However, a main effect of condition was demonstrated on Force200 (F = 19.181; p < 0.001; ηp2= 0.013). Post-hoc comparisons revealed higher Force200 values in SUST-1 (mean difference [MD] = 549 ± 137 N; d = 1.049; p < 0.001) and SUST-3 (MD = 348 ± 112 N; d = 0.665; p = 0.002) compared to the SUST-9 condition. None of the ICAs used in the present study had any effect on the CMJ performance. However, the significantly higher Force200 values noted in the SUST-1, and SUST-3 conditions compared to the SUST-9 condition suggest that the specific distributions of isometric contraction influence the force generated during their execution.
- MeSH
- Adult MeSH
- Isometric Contraction * physiology MeSH
- Muscle, Skeletal * physiology MeSH
- Humans MeSH
- Young Adult MeSH
- Resistance Training * methods MeSH
- Athletic Performance * physiology MeSH
- Muscle Strength physiology MeSH
- Check Tag
- Adult MeSH
- Humans MeSH
- Young Adult MeSH
- Male MeSH
- Publication type
- Journal Article MeSH
Obesity is associated with increased sympathetic nervous system activation, possibly contributing to higher cardiovascular risk. The aim of this study was to assess the relationship between body adiposity and sympathoadrenergic contractions in rat isolated mesenteric arteries, and the modulatory effect of mesenteric perivascular adipose tissue (PVAT). Experiments were performed on male 38-week-old Wistar, Zucker lean (ZL) and Zucker diabetic fatty (ZDF) rats. Paired rings of isolated rat superior mesenteric arteries with or without PVAT were prepared and connected to a force-displacement transducer for the recording of isometric tension. Contractile responses were elicited by increasing doses of exogenous noradrenaline and by endogenous noradrenaline released during electrical stimulation of perivascular adrenergic nerves. In ZDF rats, mesenteric PVAT had marked anticontractile effect leading to significant reduction in adrenergic contractions of their superior mesenteric arteries; however, in arterial preparations without PVAT, obese rats showed significantly increased sensitivity in their contractile responses to adrenergic stimulation when compared to other rat groups. In Wistar rats, ranging in the level of body adiposity between ZL and ZDF rats, neurogenic contractions in arterial preparations with preserved PVAT were higher compared to those without PVAT. No vasomodulatory effect of PVAT was detected in mesenteric arteries from ZL rats. The results of this study indicate that the modulatory effect of mesenteric PVAT on arterial adrenergic contractions did not change in proportion with increasing adiposity; however, it could be influenced by the rat strain-specific distribution of sympathetic nerves between PVAT and the proper mesenteric arterial wall. In ZDF rats, characterized by higher vascular sympathetic tone, the mesenteric arteries might be specifically regulated by the anticontractile effect of PVAT, leading to higher mesenteric blood flow. This could be associated with hyperphagia and increased nutrient-induced mesenteric vasodilatation in this rat strain.
- MeSH
- Adiposity * MeSH
- Mesenteric Artery, Superior innervation MeSH
- Species Specificity MeSH
- Electric Stimulation MeSH
- Disease Models, Animal MeSH
- Norepinephrine pharmacology MeSH
- Obesity physiopathology MeSH
- Rats, Wistar MeSH
- Rats, Zucker MeSH
- Sympathetic Nervous System drug effects metabolism physiopathology MeSH
- Vasoconstriction * drug effects MeSH
- Animals MeSH
- Check Tag
- Male MeSH
- Animals MeSH
- Publication type
- Journal Article MeSH
- Comparative Study MeSH
