Aim: The aim of this study was to investigate the effects of performing an isometric conditioning contraction (CC) consisting of two sets of five seconds maximal voluntary contraction in physically active individuals prior to three sets of Loaded Squat Jumps (LSJ). Method: 5 males and 4 females (mean ± SD: age 25 ± 2 years, height 175 ± 10 cm, body mass 70 ± 15 kg) were assessed on their power output, force production, jump height and velocity on three sets of LSJ on two separate sessions. Each participant attended two sessions in randomized order: a control session (CON) and an experimental session (EXP) separated by at least two hours. The EXP session consisted of a 10 min warm-up followed by 2 x 5 seconds isometric CC, this was proceeded by another two minutes of rest before three sets of LSJ were performed, each set separated by a two-minute rest. During the CON session a two-minute rest, followed by three sets of LSJ, replaced the isometric CC sequence. Results: No significant improvement was found on any of the physical parameters assessed, comparing the CON and EXP session (p > 0.05). The results showed a variance on individual response were some subjects performed better after the CC and others did not . Conclusion: In conclusion, this study evaluated the effect of performing an isometric CC prior three sets of LSJ. The results indicate that an isometric CC consisting of two sets of five seconds maximal voluntary contraction is insufficient to enhance the performance in an LSJ.

No description available.

Femoroacetabular impingement (FAI) is a hip joint deformity that causes joint pain, decreases joint range of motion and results in abnormal kinematic and kinetic characteristics. It is not known whether these biomechanical variations are caused by the actual mechanical impingement aspect of hip deformity or neuromuscular adaptations and soft tissue damage associated with pain. The purpose of this study was to investigate the effects of femoroacetabular cam deformity (FAD) during daily functional tasks. This was accomplished by measuring and comparing the hip joint biomechanics of symptomatic FAI (sFAI), asymptomatic FAD, and control (CON) subjects. Fifty one subjects volunteered to the study (n = 51; CON = 17, FAD = 18, sFAI = 16) and they performed 6 simulated activities of daily living: stair ascent and descent, sit-to-stand and stand-to-sit, dynamic range of motion, maximum depth squats and level walking tasks while motion ground reaction force and muscle activity were recorded. However, only the squat and level walking tasks were analyzed for this thesis. For each task, three-dimensional kinematics and kinetics were recorded and analyzed. Qualitative questionnaires (HOOS and WOMAC) and physical exams were also part of the testing protocol, and maximum voluntary isometric contractions (MVIC) were collected as part of a separate EMG protocol. The EMG results were not analyzed but the MVIC results were and the moments of force were determined. The sFAI group had significantly reduced scores for all HOOS and WOMAC metrics compared to FAD and CON. The sFAI group had significantly reduced external rotation, internal rotation, and a trend indicating reduced hip flexion compared to FAD and CON groups. The FAD group had a trend indicating reduced internal rotation compared to CON. There were no differences in the moments of force between groups for the MVICs. No statistically significant differences were observed between groups for the squat trials, however, the sFAI group showed biomechanical variations. Both the CON and FAD groups were able to squat deeper, had greater pelvic range of motion and a larger maximum hip and knee flexion angle compared to sFAI. Similarly, the walking tasks did not elucidate any between group differences in biomechanical characteristics. Yet, there was a noticeable trend of decreased peak hip abduction angle in the sFAI group compared to CON. This result may be indicative of a gait adaptation based on the pain that sFAI subjects endure over a long period of time. Interestingly, the FAD group did not have obvious gait patterns similar to either the CON or sFAI, making it unclear if the asymptomatic cam deformity has any gait adaptation effects. Since no differences were observed between FAD and CON in squatting and walking, the actual bone deformity may not be the cause of restricted motion during daily activities as previously thought. Internal rotation physical examination appears to indicate potential restrictions in the FAD compared to CON, and may be the best parameter to assess differences between groups and predict the presence of cam deformity. It is suggested that the presence of pain, caused by soft tissue damage over time, may be confounding factors leading to the biomechanical and neuromuscular discrepancies observed in sFAI, and should be the next avenue of study.

Femoroacetabular impingement (FAI) is a hip joint deformity that causes joint pain, decreases joint range of motion and results in abnormal kinematic and kinetic characteristics. It is not known whether these biomechanical variations are caused by the actual mechanical impingement aspect of hip deformity or neuromuscular adaptations and soft tissue damage associated with pain. The purpose of this study was to investigate the effects of femoroacetabular cam deformity (FAD) during daily functional tasks. This was accomplished by measuring and comparing the hip joint biomechanics of symptomatic FAI (sFAI), asymptomatic FAD, and control (CON) subjects. Fifty one subjects volunteered to the study (n = 51; CON = 17, FAD = 18, sFAI = 16) and they performed 6 simulated activities of daily living: stair ascent and descent, sit-to-stand and stand-to-sit, dynamic range of motion, maximum depth squats and level walking tasks while motion ground reaction force and muscle activity were recorded. However, only the squat and level walking tasks were analyzed for this thesis. For each task, three-dimensional kinematics and kinetics were recorded and analyzed. Qualitative questionnaires (HOOS and WOMAC) and physical exams were also part of the testing protocol, and maximum voluntary isometric contractions (MVIC) were collected as part of a separate EMG protocol. The EMG results were not analyzed but the MVIC results were and the moments of force were determined. The sFAI group had significantly reduced scores for all HOOS and WOMAC metrics compared to FAD and CON. The sFAI group had significantly reduced external rotation, internal rotation, and a trend indicating reduced hip flexion compared to FAD and CON groups. The FAD group had a trend indicating reduced internal rotation compared to CON. There were no differences in the moments of force between groups for the MVICs. No statistically significant differences were observed between groups for the squat trials, however, the sFAI group showed biomechanical variations. Both the CON and FAD groups were able to squat deeper, had greater pelvic range of motion and a larger maximum hip and knee flexion angle compared to sFAI. Similarly, the walking tasks did not elucidate any between group differences in biomechanical characteristics. Yet, there was a noticeable trend of decreased peak hip abduction angle in the sFAI group compared to CON. This result may be indicative of a gait adaptation based on the pain that sFAI subjects endure over a long period of time. Interestingly, the FAD group did not have obvious gait patterns similar to either the CON or sFAI, making it unclear if the asymptomatic cam deformity has any gait adaptation effects. Since no differences were observed between FAD and CON in squatting and walking, the actual bone deformity may not be the cause of restricted motion during daily activities as previously thought. Internal rotation physical examination appears to indicate potential restrictions in the FAD compared to CON, and may be the best parameter to assess differences between groups and predict the presence of cam deformity. It is suggested that the presence of pain, caused by soft tissue damage over time, may be confounding factors leading to the biomechanical and neuromuscular discrepancies observed in sFAI, and should be the next avenue of study.

Orientador: Antonio Carlos de Moraes / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Educação Física / Made available in DSpace on 2018-08-18T10:39:27Z (GMT). No. of bitstreams: 1 Batista_AlexandreRosas_M.pdf: 1979642 bytes, checksum: 55273546a63064fe915ef9261d5c5750 (MD5) Previous issue date: 2011 / Resumo: O propósito do presente estudo foi comparar as respostas eletromiográficas dos músculos vasto lateral (VL), reto femoral (RF) e bíceps femoral (BF) durante exercício de agachamento em três protocolos distintos de treinamento com pesos: a) métodos de cargas crescentes (12-10-8-6 repetições), b) método de cargas decrescentes (6-8-10-12 repetições); c) método de cargas constantes (4x9 repetições). Participaram do estudo 7 indivíduos saudáveis do sexo masculino (idade = 18 a 35 anos). Para a coleta dos sinais eletromiográficos, foram utilizados eletrodos bipolares ativos colocados nos músculos VL, RF e BF do lado dominante do voluntário, como sugere a padronização do SENIAN. Para a análise estatística a ANOVA One-way foi utilizada para comparar o valor médio da root mean square (RMS) e frequência mediana (FM) nas quatro séries para cada músculo analisado. A ANOVA Two-way foi utilizada para comparar a RMS e a FM dos músculos VL, RF e BF nas quatro séries dos três protocolos. O post-hoc de Bonferroni foi utilizado para a localização das diferenças quando apontadas pela ANOVA. O nível de significância adotado para todas as análises foi de p<0,05. Diferenças significativas foram observadas entre as séries 1, 3 e 4 do protocolo 1 quando comparado com o protocolo 2 (p<0,05). Observou-se também diferença significativa entre a série 1 do protocolo 2 e sua série correspondente do protocolo 3 e entre a série 4 do protocolo 3 quando comparada com a série 4 do protocolo 1. Entretanto, não foram encontradas diferenças entre os valores médios das quatro séries de cada protocolo de treinamento. Conclui-se que o padrão de recrutamento e ativação dos músculos VL, RF e BF são iguais para os protocolos de cargas crescentes, decrescentes e contínuas / Abstract: The purpose of this study was to compare the electromyographic responses of the vastus lateralis (VL), rectus femoralis (RF) and biceps femoralis (BF) during squatting exercise at three different protocols of weight training: 1) protocol of increasing loads (12-10-8-6 repetitions); 2) protocol of decreasing loads (6-8-10-12 repetitions); 3) protocol of constant loads (4x9 repetitions). Seven healthy male subjects were included into the study (age range: 18-35 years). To evaluate the electromyographic signal, active bipolar electrodes were placed in the muscles VL, RF and LF on the dominant side of the volunteer, as suggested by the standardization of SENIAN. For statistical analyses, One-way ANOVA was used to compare the root mean square (RMS) and median frequency (MF) in four series for each muscle examined. Two-way ANOVA was used to compare the RMS and MF of VL, RF and LF muscles in the four series of three protocols. The post-hoc Bonferroni test was used to locate the differences when indicated by ANOVA. The level of significance for all tests was 5%. Significant differences were observed between first, third and fourth series of Protocol 1 when compared with protocol 2 (p <0.05). We also observed a significant difference between the first series of protocol 2 and its corresponding series of protocol 3. Finally, significant differences were found between the third and fourth series of protocol 3, compared with the fourth series of Protocol 1. However, there were no differences between mean values of the four series of each training protocol. We conclude that the pattern of recruitment and activation of muscles VL, RF and LF are the same when using training protocols of increasing, decreasing or constant loads / Mestrado / Ciencia do Desporto / Mestre em Educação Física

Abstract available in the 10th Annual Coaches and Sport Science College .

Surgical interventions on the hip joint have greatly increased over the past decade, with the cumulative cost total hip arthroplasties (THA) alone exceeding $400B/year by 2020. Although positive patient-reported outcomes and satisfaction after THA and hip preservation for cam femoroacetabular impingement (FAI) are among the highest in orthopaedics, a limited number of research has investigated the biomechanics of dynamic activities following-up the surgery. This doctoral thesis examined the kinematics, muscle force component, and hip contact loading in pre- and postoperative patients during the deep squat motion. Specifically, this research: 1) examined muscle strength and pelvic kinematics in asymptomatic FAI, 2) examined lower-limb kinematics and muscle activity in postoperative patients who underwent either THA or FAI correction during a deep squat task, and 3) examined muscle force contributions and hip contact forces (HCF) during dynamic motion in postoperative FAI patients. First, clinical and medical imaging evaluations classified the participants into three groups: symptomatic FAI, asymptomatic FAI (FAD – participants had the cam deformity, but no pain), and healthy controls. The FAD participants had significantly greater hip extensor strength compared to the FAI and CTRL groups, which allowed them to achieve greater pelvic mobility and squat as deep as the CTRL group. Second, at the follow-up for the FAI surgery the patients showed increased pelvic ROM during the squat, and weakness associated with hip flexion and hip flexion-with-abduction were associated with postoperative alterations. For the THA follow-up analyses, the patients using a dual- mobility (DM) prosthesis reached an anterior pelvic tilt similarly to the CTRL during the dynamic parts of the squat; however, without returning its neutral tilt at the bottom of the squat, while the single- bearing (SB) prosthesis was associated with excessive hip abduction during the squat. Third, a generic full-body musculoskeletal model (MSKM) was optimized to allow for the analysis of tasks with a high range of motion (ROM; e.g. deep squat task), which controlled muscle moment arms during the high joint flexions to avoid the model’s motor tendon units (MTU) to penetrate the bony structures and respect the anatomical via points. Simulation performed during gait demonstrated that FAI patients enhance medial-lateral hip stability postoperatively, allowing reduced dynamic forces of the muscles associated with the sagittal aspect of the gait due to a less compensatory strategy to stabilize the hip joint. Furthermore, simulations performed during deep squat showed a higher anterior pelvic tilt in postoperative FAI patients as a ‘restore to native’ mechanism once the cam-deformity was no longer present. Increased semimembranosus force was linked to higher vertical HCF and total magnitude. The outcomes of this research include findings for gait and squat analyses that provide a better understanding of the pelvic mobility and hip muscle forces in hip diseases. In silico models can improve biomechanical assessment of postoperative patients in order to quantify surgical effectiveness and support clinicians in making subject-specific case decisions. The contributions also lay on the assertion of helping us to formulate future research directions in biomechanics applied to the orthopaedics field.

The purpose of this study was to understand the relationship between back squat one-repetition maximum relative to body mass (1RMrel), countermovement jump height (CMJH), and optimal drop height in drop jump (DHopt). Fifteen male participants with various sport backgrounds and training experience completed a one repetition maximum (1RM) back squat, maximum countermovement jump (CMJ), and drop jumps (DJ) from incrementally increasing drop heights to determine which drop height elicited the greatest jump height. The DHopt testing protocol was unique in that smaller increments were used to determine DHopt compared to what has been reported in literature previously. Pearson correlation coefficients revealed that DHopt had small (r=0.214) and moderate (r=0.464) relationships with 1RMrel and CMJH, respectively. A second analysis (n=13) was conducted after two participants (i.e. powerlifters) were identified as possibly being representative of a different population. The second analysis found that DHopt had strong relationships with 1RMrel (r=0.645) and CMJH (r=0.690). Results from this study seem to suggest that individuals with greater 1RMrel and CMJH tend to have a higher DHopt. However, this relationship may not be observed among all populations due to likely differences in sport background, genetics, and/or training experience.

The purpose of this study is to develop a prediction equation for (performance variables) vertical jump, broad jump, 40-yard sprint time, and pro-agility shuttle time using body mass and 1-RM values of strength for bench press and back squat. Participants (n = 76) used in the study were members of the University of South Florida D-1 football team in fall of 2009. Squat/BM demonstrated the strongest relationship in both correlation and multiple regression data for every performance variable. Squat 1-RM and Squat/BP indicated a decreased relationship and negative impact on performance. Results indicate that with increased Squat/BM improvement for all performance variables can be achieved. In addition analysis divided the entire football team into three positions (AT, LN, and SK), and noted differences for 10 of the possible 12 mean comparisons of performance variables.

The purpose of the study was to compare the kinematics of the barbell back squat between two footwear conditions and to evaluate the results with respect to recommendations put forth in the National Strength and Conditioning Association position statement for proper squat technique. Twenty-five subjects with 5 - 7 years of resistance training experience participated. Selected kinematics were measured during a 60% of 1RM barbell back squat in both barefoot and athletic shoe conditions. Paired-samples T tests were performed to compare the two footwear conditions. Significant differences were found in trunk (50.72±8.27 vs. 46.97±9.87), thigh (20.94±10.19 vs. 24.42±11.11), and shank segment angles (59.47±5.54 vs. 62.75±6.17), and knee joint angles (81.33±13.70 vs. 88.32±15.45) at the peak descent position. Based on the kinematic analysis of the barefoot squat, two kinematic advantages are countered by two disadvantages. Coaches and instructors should acknowledge these results with respect to a performer's capability, and be aware the advantages and disadvantages of barefoot squat from a kinematic perspective.