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The aim of the present study was to assess the effects of beta-alanine supplementation on muscle strength and thickness. Nineteen resistance-trained men (age: 27.3 ± 5.5 years; height: 178 ± 10 cm; body mass: 83.4 ± 9.7 kg; training experience: 5.9 ± 3.9 years) were allocated to one of the following groups: Beta-alanine (BA) (6.4 g/day of beta-alanine) or Placebo (PLA) (6.4 g/day of maltodextrin). Subjects completed 4 resistance training sessions per week for 8 weeks. The following assessments were performed before and after intervention periods: 1 repetition maximum (1RM) and 60%1RM tests in the bench press (60%1RM BENCH ) and back squat (60%1RM SQUAT ) exercises; muscle thickness assessment of biceps brachialis (MT BB ), triceps brachialis (MT TB ) , and vastus lateralis (MT VL ) by ultrasonography. No significant difference between groups was observed for the absolute increase (pre-post intervention) in the 1RM BENCH (mean difference = 0.8 kg; p = 0.679), 1RM SQUAT (mean difference = 0.1 kg; p = 0.992), MT BB (mean difference = 0.7 mm; p = 0.637), MT TB (mean difference = 1.4 mm; p = 0.282), MT VL (mean difference = 1.6 mm; p = 0.311), 60%1RM BENCH (mean difference = 0.5 repetitions; p = 0.670) and 60%1RM SQUAT (mean difference = 0.7 repetitions; p = 0.690). In conclusion, the 8-week training period induced significant strength and morphological responses. However, the addition of beta-alanine supplementation did not enhance these adaptive outcomes., Competing Interests: The authors declare have not potential conflict of interest in relation to this paper., (Copyright © Biology of Sport 2023.)

The regular practice of resistance training (RT) has been shown to induce relevant increases in both muscle strength and size. In order to maximize these adaptations, the proper manipulation of RT variables is warranted. In this sense, the aim of the present study was to review the available literature that has examined the application of the acute training variables and their influence on strength and morphological adaptations of healthy young adults. The information presented in this study may represent a relevant approach to proper training design. Therefore, strength and conditioning coaches may acquire a fundamental understanding of RT-variables and the relevance of their practical application within exercise prescription.

The present study investigated acute muscular performance and metabolic responses to resistance training (RT) with inter-set stretching (ISS). Seventeen resistance-trained men (age: 30.0 ± 5.6 years; body mass: 81.8 ± 13.4 kg; height: 173 ± 6.2 cm; RT experience: 4.6 ± 1.7 years) completed the ISS and traditional training (TT) protocol seven days apart in a randomized order. In both protocols, 7 sets of the seated cable fly exercise were performed with a 10-repetition maximum (10-RM) load. During the ISS protocol, subjects completed inter-set passive static stretching of the agonist muscles for 45 seconds, while a passive rest (no stretching) was adopted for the same duration in the TT protocol. The change in maximal bench press strength (1-RM), muscle swelling (ultrasound) of the pectoralis major (PM MS ), and blood lactate were assessed immediately following each protocol. Additionally, the total load lifted (TLL) and internal training load (ITL) were assessed in both protocols. There was no difference between protocols for the change in maximal bench press 1-RM ( p > 0.05). There were higher values for PM MS ( p < 0.05) and blood lactate ( p < 0.05) following the TT versus the ISS protocol. The TT resulted in higher TLL ( p < 0.05) and ITL values ( p < 0.05) versus the ISS protocol. Resistance training with inter-set stretching results in lower acute performance and metabolic responses versus traditional training with passive rest between sets. Therefore, inter-set stretching might be applied within a periodized program on lower intensity days to reduce the overall stress of a session.

The recovery manipulation during high-intensity interval training (HIIT) may have the potential to modulate the responses of post-exercise energy metabolism. The purpose of this study was to investigate how the type ( i.e ., passive and active) and duration ( i.e ., short and long) of the recovery between the intervals in HIIT affect the excess post-exercise oxygen consumption (EPOC) and oxidation of fats and carbohydrates during the post-exercise recovery. Eight physically active men performed a maximal incremental test, to determine the peak oxygen consumption (V̇O 2 peak) and the first ventilatory threshold (VT), and four HIIT exercise sessions on a treadmill. The HIIT exercise sessions consisted of 5 intervals interspersed with 4 recovery periods; each interval was sustained until exhaustion, and the intensity was set at the V̇O 2 peak velocity; recoveries were passive, active (VT velocity), short (2-min), or long (8-min). The HIIT exercise sessions were performed in a random and crossed manner. After the HIIT exercise sessions, EPOC and oxidation of fats and carbohydrates were measured during the 120-min of post-exercise recovery. There were no differences in the EPOC among the exercise sessions ( p = 0.56). There were no differences among the exercise sessions in the amount of energy expended on the oxidation of fats ( p = 0.78) and carbohydrates ( p = 0.91) during the post-exercise recovery. The recovery manipulation during HIIT does not affect the EPOC and post-exercise fat and carbohydrate oxidation. One can choose the type and duration of recovery, knowing that the post-exercise substrate oxidation and EPOC responses will be preserved.

The aim of the present study was to assess the short-term effects of four weeks of beta-alanine supplementation (BA) (6.4 g/day) on the total volume performed and perceived effort of resistance-trained individuals. Sixteen trained men (age: 27.3 ± 5.0 years, height: 1.78 ± 0.1 cm, total body mass: 84.3 ± 8.4 kg, RT experience: 5.9 ± 3.3 years) were allocated in one of the following groups: BA or Placebo (PLA). In addition, during the same period, participants were submitted to a resistance training program. Volume index (VI) and the rate of perceived exertion (RPE) were collected during the experimental period for both groups. Significant increases from the first to the last intervention week in VI were observed only for BA (+6.5%, d = 0.61, p = 0.04). In addition, supplementation induced a lower mean RPE (BA: 8.8 ± 0.5 AU vs. PLA: 9.4 ± 0.3 AU, p = 0.02). In conclusion, four weeks of BA supplementation were able to increase resistance-training volume without affecting the perceived effort of trained men.

The aim of the present study was to assess the chronic effects of different order of resistance training cycles on strength and muscle thickness of recreationally resistance-trained men. The study sample was composed of 16 healthy men (age: 25.0 ± 3.8 years, height: 1.77 ± 7.6 cm, total body mass: 81.7 ± 10.4 kg, RT experience: 4.6 ± 0.7 years, relative bench press one repetition maximum: 1.2 ± 0.1, relative squat one-repetition maximum: 1.5 ± 0.2). According to baseline maximal strength, participants were allocated in one of the following groups: Maximal Strength-Strength Endurance (MS-SE) (six weeks of a maximal strength cycle followed by six weeks of a strength endurance cycle); Strength Endurance -Maximal Strength (MS-SE) (six weeks of a strength endurance cycle followed by six weeks of a maximal strength cycle). The following measurements were performed in the pre and post intervention periods: one-repetition maximum (1RM) on parallel back squat and bench press exercises, muscle thickness evaluation of biceps brachialis (MT BB ), triceps brachialis (MT TB ), and vastus lateralis (MT VL ) by ultrasonography. Total load lifted (TLL) and Internal training load (ITL) were also assessed. Both groups presented significant increases in bench press (MS-SE p = 0.001, SE-MS p = 0.003) and half squat (MS-SE p = 0.004, SE-MS p = 0.001) 1RM, MT BB (MS-SE p = 0.020, SE-MS p = 0.005) and MT TB (MS-SE p = 0.001, SE-MS p = 0.001). For MT VL , a significant increase was observed only for MS-SE group (MS-SE p = 0.032, SE-MS p = 0.143). No significant difference between groups was observed for any strength or morphological outcomes. In conclusion, both MS-SE and SE-MS training cycles are effective strategies to enhance resistance training adaptations in trained men.

The type of exercise is a relevant resistance training-variable that might be manipulated in order to induce significant increases in muscle strength. The aim of this study was to analyze the influence of multi-joint vs single-joint resistance exercises on maximal strength. Sixteen resistance-trained men (age: 23.1 ± 4.4 years; body mass: 86.0 ± 12.8; height: 177.9 ± 6.4 cm; training experience: 4.2 ± 3.4 years) performed one of the following training protocols for six weeks: MULTI, consisting of only multi-joint exercises or SINGLE, consisting of only single-joint exercises. Subjects were then submitted to a three-week washout period, before being submitted to the other protocol for another six weeks. A linear periodization model was adopted in which external load was increased and the repetition range was decreased every two weeks. Maximal dynamic strength of bench press (1RM BENCH ) and squat exercises (1RM SQUAT ), a percentage variation of total load lifted (ΔTLL) and internal training load (ITL) were measured. Similar increases in 1RM BENCH (MULTI: 10.8%, p < 0.001; SINGLE: 5.5%, p < 0.001) and 1RM SQUAT (MULTI: 19.7%, p < 0.001; SINGLE: 19.0%, p < 0.001) were observed after the MULTI and SINGLE protocols. A decrease in TLL was detected for both exercise protocols; however, the SINGLE protocol induced a greater decrease, compared to the MULTI protocol (-35 ± 11% vs -42 ± 5%, respectively; p = 0.026). A greater ITL for the MULTI was observed when compared to the SINGLE (12.1%; p < 0.001). In conclusion, resistance training protocols with different exercise modalities seem to produce similar strength increases in resistance-trained men.

Effective chemical control relies on reducing vector population size. However, insecticide selection pressure is often associated with the development of resistant populations that reduce control success. In treated areas, these resistant individuals present an adaptive advantage due to enhanced survival. Resistance can also lead to negative effects when the insecticide pressure ceases. In this study, the biological effects of deltamethrin resistance were assessed in the Chagas disease vector Triatoma infestans. The length of each developmental stage and complete life cycle, mating rate, and fecundity were evaluated. Susceptible and resistant insects presented similar mating rates. A reproductive cost of resistance was expressed as a lower fecundity in the resistant colony. Developmental costs in the resistant colony were in the form of a shortening of the second and third nymph stage duration and an extension of the fifth stage. A maternal effect of deltamethrin resistance is suggested as these effects were identified in resistant females and their progeny independently of the mated male's deltamethrin response. Our results suggest the presence of pleiotropic effects of deltamethrin resistance. Possible associations of these characters to other traits such as developmental delays and behavioral resistance are discussed., (© 2015 The Society for Vector Ecology.)