The Impact of Squat Velocity on Force, Power, and Muscle Activity

The squat is a thoroughly examined movement pattern and commonly used in sport performance training protocols, rehabilitation programs, and recreational exercise. Previous research measuring absolute strength has shown hamstring muscle activity in a six-repetition max barbell back squats. PURPOSE: The purpose of this study is to examine the effects of varying squat velocities (25, 50, 75 deg/s) on force, power, and the activation of the quadricep and hamstring muscles. Using a single-blind randomized research design, we hypothesized that hamstring muscle activity will increase at faster squat velocities. Our secondary hypothesis is that peak power will occur at 50 deg/s and peak force will occur at 25 deg/s. Muscle activity for both the hamstring and quadriceps was measured as root mean square (RMS) electromyography (EMG) and expressed as a percentage of the maximum voluntary contraction (MVC). Muscle activity, force output, and power output were measured over five consecutive repetitions of each velocity in a randomized order. METHODS: Twelve healthy adults (10 males, 2 females) participated in this investigation. Three Delsys Trigno EMG electrodes were placed on the right leg of all participants as they performed the MVC and squat trials on the isokinetic machine. One was placed on the posterior side (biceps femoris [BF]) to measure hamstring activity and two were placed on the anterior side (vastus medialis [VM] and vastus lateralis [VL]) to measure quadricep activity. An isokinetic training machine was used to test the participant’s squat performance at pre-set velocities (Ariel Computerized Exercise System, CA). These machines have been used to measure force and power relationships. MVC was found using an adjustable bench with a padded immovable leg extension attachment. For the quadriceps, the participant sat on the bench in an upright position with the leg extended to approximately 110 degrees against the attachment. Hamstring MVC was measured in a standing position with the leg of interest flexed to approximately 110 degrees with the leg extension attachment behind the lower leg. Three trials of MVC were performed for both knee flexion and extension so results during squat trials can be expressed as a percentage of MVC. Following the MVC, participants then underwent experimental trials. The squat movement pattern was standardized to a depth of 90 degrees of knee flexion measured via goniometry and maintained during each trial using an adjustable height box, set to a predetermined height. Feet were instructed to remain at approximately shoulder width with knees tracking along the same line as the feet to avoid knee misalignment to avoid injury and potentially alter muscle activity. Five consecutive repetitions at each velocity (25, 50, and 75 deg/s) were performed with at least two minutes of rest between trials. For each trial, repetitions two, three, and four were used to determine average and peak power and force. RESULTS: To determine the magnitude of BF muscle activity, we compared it to the degree of quadricep muscle activity (VL:BF and VM:BF) for each squat velocity and analyzed using a one-way ANOVA. This relative hamstring muscle activity was highest at 75 deg/s for VL:BF at 3.84% and at 50 deg/s for VM:BF at 4.59% However, the difference in BF activity involved at each squat velocity was not statistically significant (p = 0.2973). The highest average peak power was achieved at a velocity of 50 deg/s with a value of 1538.19 ± 717.2 W. The greatest average peak force was found at a velocity of 25 deg/s with a value of 1574.08 N ± 605.8 W. When analyzing the peak force within the three velocity groups, a statistically significant difference was found with a p \u3c 0.0001. This was also seen with the average force within the three velocity groups with a p \u3c 0.0001. No statistically significant difference was found for either peak or average power among the three velocity groups. CONCLUSION: When comparing the degree of BF involved during the squat movement, the 25 deg/s had the lowest relative to the quadricep musculature, while both the 50 deg/s and 75 deg/s had higher relative BF activity. As expected, a U-trend was observed with average peak power observed at 50 deg/s, with a decrease at both 25 and 75 deg/s – further confirming the established power-velocity relationship. However, this difference was not statistically significant with our participant size. As velocity increased, force decreased – further confirming the established force-velocity relationship. These results proved to be statistically significant

Validation of a small scale woody biomass downdraft gasification plant coupled with gas engine

In recent years, small scale cogeneration systems (< 500 kWe) distributed in different geographical locations using biomass has received special attention as economically competitive and environmentally friendly ways of producing energy. These systems can be integrated to industrial and agricultural activities where biomass residues are generated and can be converted into electricity and thermal energy by combustion or gasification. The legislations of many European countries such as Italy concerning renewable energy and energy efficiency along the taxation schemes have raised the incentives for small scale cogeneration plants. Consequently, there is a clear economic interest of the companies in this sector and there is also a scientific interest towards demonstration of their energetic efficiency, environmental performance and reliability. Among the suggested technologies for the biomass conversion into energy, downdraft gasification (using air as gasification agent), coupled with internal combustion engines, has the advantage of high electric efficiency (~ 25%) and low tar generation, making easier the gas cleaning process necessary for its use into engines. In the present work, the results of a measurement campaign performed on a commercial scale 350 kWth downdraft woodchips gasification plant, coupled with an SI internal combustion engine (ICE), are presented and discussed. The main goals of this first experimental campaign have been to verify the stability of gasifier and engine operation, operability of the plant and to determine its energy efficiency. The campaign verified a stable operation of the gasifier and the plant produced a syngas with a composition suitable for a gas engine. The energy balance resulted in a potential overall wood fuel to electricity efficiency of about 23 %

Are Vascularized Fibula Autografts a Long-lasting Reconstruction After Intercalary Resection of the Humerus for Primary Bone Tumors?

BackgroundA vascularized fibula graft (VFG) is the vascular autograft most frequently used to restore large segmental long bone defects, particularly in the upper limb. Because the use of a vascularized fibula involves an operation in an uninvolved extremity with potential morbidity, it is important to document that this type of reconstruction is successful in restoring function to the humerus. However, the long-term results of VFG after intercalary resection of the humeral diaphysis for bone tumors are still unknown.Questions/purposes(1) What was the complication rate of reconstruction? (2) What was the functional result after surgical treatment, as assessed by the Musculoskeletal Tumor Society (MSTS) score, the American Shoulder and Elbow Society (ASES) score, and Constant score? (3) What was the survivorship of these grafts free from revision and graft removal at 5, 10, and 15 years?MethodsBetween 1987 and 2021, 127 patients were treated at our institution with en bloc resection for a primary malignant or an aggressive benign bone tumor of the humerus; we excluded patients treated with extra-articular resection or amputation. Of those, 14% (18 of 127) were treated with intercalary resection of the humeral diaphysis for primary bone tumors and reconstruction with VFG, with or without a bulk allograft, and were analyzed in this retrospective study. Generally, our indications for reconstruction with VFG are intercalary resection of the humerus for primary malignant or aggressive benign bone tumors in patients with long life expectancy and high functional demands, in whom adequate bone stock of the proximal and distal epiphysis can be preserved. In 13 patients, VFG was used alone, whereas in five patients, a massive allograft was used. Our policy was to use VFG combined with a massive allograft in patients undergoing juxta-articular joint-sparing resections in which proximal osteotomy was performed close to the anatomic neck of the humerus to obtain more stable fixation and better tendinous reattachment of the rotator cuff and deltoid. All 18 patients who were treated with a VFG were available for follow-up at a minimum of 2 years (median follow-up 176 months, range 26 to 275 months), and although three have not been seen in the past 5 years and are not known to have died, they had 172, 163, and 236 months of follow-up, and were included. The median age at surgery was 25 years (range 2 to 63 years), the median humeral resection length was 15 cm (range 8 to 21 cm), and the median fibular length was 16 cm (range 12 to 23 cm). Complications and functional scores were ascertained by chart review that was performed by an individual not involved in patient care. Functional results were assessed with the MSTS score (range 0 to 30), the ASES score (range 0 to 100), and the Constant score (range 0% to 100%). Survivorship was estimated using a Kaplan-Meier survivorship estimator, which was suitable because there were few deaths in this series.ResultsSeven patients underwent a revision procedure (one radial nerve transient palsy because of screw impingement, four nonunions in three patients with one humeral head avascular necrosis, treatment for screw-related pain in one patient, and two VFG fractures), and one patient underwent VFG removal. Donor site complications were observed in four patients (one ankle valgus deformity and three claw toes - the first toe in two patients and the other toes in the third). At the final clinical control, at a median follow-up of 176 months (range 26 to 275 months), the median MSTS score was 30 of 30 (range 28 to 30), the median ASES score was 98.3 (range 93 to 100), and the median Constant score was 93.5% (range 79% to 100%). Revision-free survival was 71% (95% CI 53% to 96%) at 5 years and 57% (95% CI 37% to 88%) at 10 and 15 years; VFG removal-free survival was 94% (95% CI 83% to 100%) at 5, 10, and 15 years.ConclusionVFG appears to be an effective reconstructive option after humeral intercalary resection for primary bone tumors. These are complex procedures and should be performed by an experienced team of surgeons who recognize that complications may occur frequently in the first years after the procedure. The frequency of mechanical complications observed in the first 5 years postoperatively may be lessened by using long spanning-plate fixation, and if successful, this reconstruction provides a long-term, durable reconstruction with excellent functional results.Level of EvidenceLevel IV, therapeutic study

Proteinuria in focal segmental glomerulosclerosis: role of circulating factors and therapeutic approach.

The clinical course of primary Focal Segmental Glomerulosclerosis (FSGS) is frequently complicated by nephrotic range proteinuria and progression to renal failure. The high recurrence rate of the disease in transplanted kidney suggests the hypothesis that such patients have a circulating factor that alters glomerular capillary permeability. In recent years some authors found that serum from patients with FSGS increases glomerular permeability to albumin and partially identified the permeability factor (PF) as a protein of 30-50 Kd m.w. The removal of this protein by means of Plasma Exchange (PE) or plasma Immunoadsorption by Protein A (IA) decreased proteinuria. In this report we provide preliminary data about the prevalence of PF and the therapeutic effect of its removal by IA, in 3 pts with recurrence in the transplanted kidney, and 4 with FSGS of the native kidneys. They were resistant to corticosteroids (CS) and immunosuppressive (IS) therapy. 10 IA sessions were performed in 4 weeks: if a remission was achieved IA was gradually tapered. The level of PF in the serum was measured by an in vitro assay to determine the glomerular permeability to albumin. The FSGS was histologically proven in all cases and the degree of evolution was evaluated. PF levels, serum creatinine, daily proteinuria and serum albumin were monitored. The 3 patients with recurrent FSGS had a normalization of the PF levels; 2 had a clinical remission. In FSGS of native kidneys PF was elevated in 3/4 cases; 1 had a clinical remission; 2 with extensive sclerohyalinosis and 1 without PF levels did not improve. Our results confirm that most patients with FSGS have high PF serum levels and suggest that its removal can be beneficial

Ferramentas de busca na internet para educação médica: vantagens e desvantagens do Google Acadêmico, Pubmed e Scielo

Os principais sítios eletrônicos gratuitos para busca de artigos científicos em Medicina são o PubMed (http://www.ncbi.nlm.nih.gov/pubmed/) e o Google Acadêmico – GA (http://scholar.google.com.br/). O Scielo (http://www.scielo.org) também é importante para a busca de artigos latino-americanos. É assumido pela comunidade médica que o PubMed é a melhor ferramenta de busca, entretanto, algumas temáticas como a educação médica podem não ser totalmente contempladas no PubMed. O objetivo é verificar se o GA pode ser uma ferramenta útil para busca de artigos científicos referenciados na temática em educação médica, com foco no currículo médico e ética, comparados ao Pubmed e ao Scielo. É um estudo transversal, com análise qualiquantitativa sobre artigos científicos completos publicados no GA, PubMed e Scielo, no período entre 01/01/2011 a 31/12/2011, levantados entre 01 a 30/06/2012. Utilizaram-se as palavras-chaves em inglês: “medical curriculum” and “ethics”. O GA obteve 321 artigos completos de acesso livre; o PubMed resgatou três e o Scielo obteve-se apenas um resultado. A diferença entre o GA e o Pubmed talvez possa ser explicada pelo tipo de revistas indexadas no Pubmed,com maior foco em ciências básicas em biologia e saúde. O baixo retorno de artigos oriundos da busca no Scielo pode ser decorrente da própria ferramenta de busca, feita apenas pelos termos indexados como palavras-chaves. A análise preliminar quantitativa aponta que o GA pode ser útil na busca de artigos em educação médica, mas a análise qualitativa dos artigos deverá ainda ser realizada e outros termos em educação médica ainda serão pesquisados

Deficiência cognitiva não impede atividade física em idosos

É queixa comum de familiar de paciente idoso, portador de deficiência cognitiva relacionada ao envelhecimento de que ele não tem condição de praticar atividade física. Para verificar esta ideia comum à população atendida na Policlínica André Bianco, foram entrevistados 36 idosos, segundo um protocolo submetido e aprovado pelo Comitê de Ética do Unifoa. Os idosos ou seus representantes, após assinarem termo de consentimento, responderam a dois questionários: o primeiro indagando da prática de atividade física. O segundo avaliando a sua atividade cognitiva, através do teste denominado de minimental, já validado por inúmeros pesquisadores internacionais e nacionais. Os resultados analisados demonstram que não há diferença significativa entre os participantes de atividade física que estão em seu pleno domínio mental (66,7% dos mentalmente saudáveis) e os praticantes de atividade que apresentam deficiência cognitiva (57,1%). O estudo demonstra que as deficiências cognitivas moderadas não constituem fator limitante à prática de exercício, que é tão importante para a manutenção das funções vitais orgânicas