The purposes of this dissertation were to examine bilateral asymmetry as a factor of postactivation potentiation, examine and compare the acute effects of ballistic and non-ballistic concentric-only half-squats on squat jump performance, and compare the potentiation and temporal profiles of strong and weak subjects following potentiation protocols that included ballistic and non-ballistic concentric-only half-squats. The following are major findings of the dissertation. Squat jump performance may be acutely enhanced following ballistic concentriconly half-squats; however the changes in performance do not appear to be related to bilateral symmetry. Ballistic concentric-only half-squats acutely improve various squat jump performance variables at various time intervals; however the changes in performance are not related to the bilateral symmetry of the subject. Ballistic concentric-only half-squats produced superior acute potentiation effects with regard to jump height, peak power, and allometricallyscaled peak power as compared to non-ballistic concentric-only half-squats and a control protocol. Stronger subjects potentiated earlier and to a greater extent as compared to their weaker counterparts. This dissertation indicates that bilateral symmetry may not be considered as an underlying factor affecting postactivation potentiation. However, it is suggested that future research should continue to investigate the factors that are associated with postactivation potentiation. The findings of this dissertation also demonstrate the importance of how an individual performs a concentric-only squatting motion. By training with ballistic movements, a greater training stimulus may be achieved as compared to training with non-ballistic movements. While this dissertation discussed the acute potentiation differences between ballistic and nonballistic concentric-only half-squats, longitudinal research is needed to determine if different training effects result from each training method. This dissertation also supports that notion that stronger individuals may benefit more with regard to potentiation effects. In order to optimize performance and realize the greatest potentiation effects, it is recommended that greater levels of relative strength should be sought. It is suggested that further research is needed on the longitudinal differences in the potentiation effects an individual can realize based on their strength levels.

This study examined and compared the acute effects of ballistic and nonballistic concentric-only half-squats (COHSs) on squat jump performance. Fifteen resistance-trained men performed a squat jump 2 minutes after a control protocol or 2 COHSs at 90% of their 1 repetition maximum (1RM) COHS performed in a ballistic or nonballistic manner. Jump height (JH), peak power (PP), and allometrically scaled peak power (PPa) were compared using three 3 × 2 repeated-measures analyses of variance. Statistically significant condition × time interaction effects existed for JH (p = 0.037), PP (p = 0.041), and PPa (p = 0.031). Post hoc analysis revealed that the ballistic condition produced statistically greater JH (p = 0.017 and p = 0.036), PP (p = 0.031 and p = 0.026), and PPa (p = 0.024 and p = 0.023) than the control and nonballistic conditions, respectively. Small effect sizes for JH, PP, and PPa existed during the ballistic condition (d = 0.28–0.44), whereas trivial effect sizes existed during the control (d = 0.0–0.18) and nonballistic (d = 0.0–0.17) conditions. Large statistically significant relationships existed between the JH potentiation response and the subject's relative back squat 1RM (r = 0.520; p = 0.047) and relative COHS 1RM (r = 0.569; p = 0.027) during the ballistic condition. In addition, large statistically significant relationship existed between JH potentiation response and the subject's relative back squat strength (r = 0.633; p = 0.011), whereas the moderate relationship with the subject's relative COHS strength trended toward significance (r = 0.483; p = 0.068). Ballistic COHS produced superior potentiation effects compared with COHS performed in a nonballistic manner. Relative strength may contribute to the elicited potentiation response after ballistic and nonballistic COHS.

The purpose of this study was to compare the temporal profile of strong and weak subjects during ballistic and nonballistic potentiation complexes. Eight strong (relative back squat = 2.1 ± 0.1 times body mass) and 8 weak (relative back squat = 1.6 ± 0.2 times body mass) males performed squat jumps immediately and every minute up to 10 minutes following potentiation complexes that included ballistic or nonballistic concentric-only half-squat (COHS) performed at 90% of their 1 repetition maximum COHS. Jump height (JH) and allometrically scaled peak power (PPa) were compared using a series of 2 × 12 repeated measures analyses of variance. No statistically significant strength level main effects for JH (p = 0.442) or PPa (p = 0.078) existed during the ballistic condition. In contrast, statistically significant main effects for time existed for both JH (p = 0.014) and PPa (p < 0.001); however, no statistically significant pairwise comparisons were present (p > 0.05). Statistically significant strength level main effects existed for PPa (p = 0.039) but not for JH (p = 0.137) during the nonballistic condition. Post hoc analysis revealed that the strong subjects produced statistically greater PPa than the weaker subjects (p = 0.039). Statistically significant time main effects existed for time existed for PPa (p = 0.015), but not for JH (p = 0.178). No statistically significant strength level × time interaction effects for JH (p = 0.319) or PPa (p = 0.203) were present for the ballistic or nonballistic conditions. Practical significance indicated by effect sizes and the relationships between maximum potentiation and relative strength suggest that stronger subjects potentiate earlier and to a greater extent than weaker subjects during ballistic and nonballistic potentiation complexes.

Submitted by Renata Lopes (renatasil82@gmail.com) on 2017-05-11T14:52:03Z No. of bitstreams: 1 marcellymancini.pdf: 2007536 bytes, checksum: 1f4ee7a77352e5ac0b51bf290af60445 (MD5) / Approved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2017-05-17T15:14:59Z (GMT) No. of bitstreams: 1 marcellymancini.pdf: 2007536 bytes, checksum: 1f4ee7a77352e5ac0b51bf290af60445 (MD5) / Made available in DSpace on 2017-05-17T15:14:59Z (GMT). No. of bitstreams: 1 marcellymancini.pdf: 2007536 bytes, checksum: 1f4ee7a77352e5ac0b51bf290af60445 (MD5) Previous issue date: 2016-12-08 / CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / As plataformas instáveis (PI) vêm sendo amplamente utilizadas nos programas de treinamento resistido com diferentes objetivos, nas quais, acredita-se que o sistema neuromuscular seja mais exigido do que na plataforma estável (PE). Assim, os objetivos do estudo foram verificar a resposta eletromiográfica dos músculos vasto lateral (VL), reto abdominal (RA), oblíquo externo (OE) e eretor espinhal (ES), em homens, durante o exercício meio agachamento em plataforma estável e instável, e identificar e comparar a resposta da percepção subjetiva do esforço (PSE) durante o teste na PE e PI. A amostra foi composta por 15 homens adultos treinados (25,0 ± 2,7 anos; 77,7 ± 6,8 kg, 174,6 ±7,3 cm; 25,5 ±1,5 kg/m² e 14,4 ± 2,6 % de gordura). O procedimento experimental consistiu na avaliação da ativação eletromiográfica dos músculos VL, RA, OE e ES durante o exercício meio agachamento em PE e PI com cargas randomizadas de 40, 50, 60 e 70% de 1-RM. Após o fim de 15 repetições em cada carga, os voluntários respondiam à escala de OMNI-RES e permaneciam em repouso para a próxima carga. Foi respeitado um intervalo mínimo de 48 horas entre os testes. A Root Mean Square (RMS) dos músculos VL, RA, OE e ES, e a PSE foram comparadas entre cada condição experimental (50%1-RM, 60%1-RM e 70%1-RM na PE, 40%1-RM, 50%1-RM e 60%1-RM na PI), por meio da análise de medidas repetidas (ANOVA), utilizando a técnica de modelos mistos. A significância estatística adotada foi de 5%. Em caso de significância, comparações pareadas post hoc foram feitas, utilizando a correção de Bonferroni. Na análise post hoc, não foram observadas diferenças significativas na ativação eletromiográfica entre as cargas na PE e PI. A PSE foi maior na condição 50% 1-RM em PI comparado a 50% 1-RM em PE (5,2 ± 2,3 vs. 3,8 ± 1,6; p = 0,04; TE = 0,72) e maior PSE na condição 60% 1-RM na PI comparado a 60% 1-RM na PE (6,1 ± 2,1 vs. 4,7 ± 1,8; p = 0,04; TE = 0,72). Em conclusão, as PI produzem uma similar atividade eletromiográfica em relação às PE mesmo utilizando uma menor carga e, para cargas de 50% e 60% de 1-RM, o esforço percebido foi significativamente maior na PI. / Unstable platforms (UP) have been widely used in resistance training programs with different objectives, in which the neuromuscular system is believed to be more required than in the stable platform (SP). Thus, the objectives of the study were to verify the electromyographic response of the vastus lateralis (VL), rectus abdominis (RA), external oblique (EO) and spinal erector (SE) muscles in men, during exercise half squatting on a stable and unstable platform, and to identify and compare the Rating of Perceived Exertion (RPE) during UP and SP testing. The sample consisted of 15 trained adult males (25.0 ± 2.7 years, 77.7 ± 6.8 kg, 174.6 ± 7.3 cm, 25.5 ± 1.5 kg / m² and 14, 4 ± 2.6% fat). The experimental protocol consisted of the evaluation of the electromyographic activation of the VL, RA, EO and SE muscles during the half squat exercise in UP with random loads of 50, 60 and 70% of 1-RM and in the UP with loads of 40, 50 and 60 % Of 1-RM, also randomized. After 15 repetitions in each load, the volunteers responded to the OMNI-RES scale and remained at rest for the next load. A minimum of 48 hours between the tests was observed. The Root Mean Square (RMS) of the muscles VL, RA, EO and SE, and RPE were compared between each experimental condition (50% 1-RM, 60% 1-RM and 70% 1-RM in SP, 40% 1-RM and 60% 1-RM in the UP), through the analysis of repeated measurements (ANOVA), using the mixed model technique. The statistical significance was 5%. In case of significance, matched post hoc comparisons were made using the Bonferroni correction. In the post hoc analysis, no significant differences were observed in the electromyographic activation between SP and UP loads. The RPE was higher in the 50% 1-RM UP condition compared to 50% 1-RM in SP (5.2 ± 2.3 vs. 3.8 ± 1.6, p = 0.04, TE = 0, 72) and higher RPE in the condition 60% 1-RM in UP compared to 60% 1RM in SP (6.1 ± 2.1 vs. 4.7 ± 1.8; p = 0.04; TE = 0, 72). The UP produced a similar electromyographic activity in relation to the SP using a lower load and, for loads of 50% and 60% of 1-RM, the RPE was significantly higher in the UP.

The purpose of this study was to examine the relationships between muscle cross-sectional area (CSA), maximal strength, power output, and maximum potentiation characteristics. The vastus lateralis and biceps femoris CSA, one repetition maximum (1RM) back squat, 1RM concentric-only half-squat (COHS) strength, static jump power output, and maximum potentiation characteristics of 17 resistance-trained men was assessed during several testing sessions. Pearson’s correlation coefficients were used to examine the relationships between CSA, strength, power output, and maximum potentiation measures. Moderate-to-strong relationships existed between CSA and strength measures (r = 0.462–0.643) as well as power output (r = 0.396–0.683). In addition, moderate-to-strong relationships existed between strength and power output (r = 0.407–0.548), while trivial relationships existed between strength and maximum potentiation (r = −0.013–0.149). Finally, small negative relationships existed between CSA and maximum potentiation measures (r = −0.229–−0.239). The results of the current study provide evidence of the interplay between muscle CSA, strength, power, and potentiation. Vastus lateralis and biceps femoris CSA may positively influence an individual’s back squat and COHS maximal strength and squat jump peak power; however, muscle CSA and absolute strength measures may not contribute to an individual’s potentiation capacity. Practitioners may consider implementing resistance training strategies that improve vastus lateralis and biceps femoris size in order to benefit back squat and COHS strength. Furthermore, implementing squatting variations—both full and partial—may benefit jumping performance.