In high impact human activities, much of the impact shock wave is dissipated through internal body structures, preventing excessive accelerations from reaching vital organs. Mechanisms responsible for this attenuation, including lower limb joint compression and spinal compression have been neglected in existing whole-body simulation models. Accelerometer data on one male subject during drop landings and drop jumps from four heights revealed that peak resultant acceleration tended to decrease with increasing height in the body. Power spectra contained two major components, corresponding to the active voluntary movement (2 Hz 14 Hz) and the impact shock wave (16 Hz 26 Hz). Transfer functions demonstrated progressive attenuation from the MTP joint towards the C6 vertebra within the 16 Hz 26 Hz component. This observed attenuation within the spine and lower-limb joint structures was considered within a rigid body, nine-segment planar torque-driven computer simulation model of drop jumping. Joints at the ankle, knee, hip, shoulder, and mid-trunk were modelled as non-linear spring-dampers. Wobbling masses were included at the shank, thigh, and trunk, with subject-specific biarticular torque generators for ankle plantar flexion, and knee and hip flexion and extension. The overall root mean square difference in kinetic and kinematic time-histories between the model and experimental drop jump performance was 3.7%, including ground reaction force root mean square differences of 5.1%. All viscoelastic displacements were within realistic bounds determined experimentally or from the literature. For an equivalent rigid model representative of traditional frictionless pin joint simulation models but with realistic wobbling mass and foot-ground compliance, the overall kinetic and kinematic difference was 11.0%, including ground reaction force root mean square differences of 12.1%. Thus, the incorporation of viscoelastic elements at key joints enables accurate replication of experimentally recorded ground reaction forces within realistic whole-body kinematics and removes the previous need for excessively compliant wobbling masses and/or foot-ground interfaces. This is also necessary in cases where shock wave transmission within the simulation model must be non-instantaneous.

O objetivo do presente estudo foi de analisar as respostas de ativação muscular e força de reação do solo de um exercício de hidroginástica com diferentes equipamentos, executado por mulheres jovens. Sendo assim, foram realizados três testes progressivos máximos em ambiente aquático, com no mínimo 48 horas de intervalo, com o exercício de chute, sem equipamento (SE), com equipamento resistivo (RE) e flutuante (FL), a fim de determinar a cadência correspondente ao segundo limiar ventilatório (LV2). O terceiro e último dia de testes consistiu primeiramente na contração voluntária isométrica máxima (CVM) em ambiente terrestre, dos músculos a serem avaliados: reto femoral (RF), bíceps femoral (BF), tibial anterior (TA) e gastrocnêmio lateral (GA). Após finalizada a CVM de cada músculo, foi feito um isolamento dos eletrodos, e então o sujeito entrou na piscina para realizar os testes de eletromiografia (EMG) e força de reação do solo (FRS) nas intensidades do LV2 e máximo esforço (MAX). Dentro da piscina, o sujeito foi posicionado na profundidade do processo xifóide e então, executou as três situações do exercício de chute (SE, RE e FL), de forma randomizada, nas intensidades LV2 e máximo esforço (MAX). Foi utilizada o teste estatístico de Equações estimativas generalizadas e o teste post-hoc de Bonferroni. Após o tratamento dos dados e análise estatística, foram encontrados maiores valores de ativação muscular da intensidade LV2 para MAX, para todas as situações nos músculos RF, BF e TA, exceto para GL que não obteve diferenças entre intensidades para a situação RE. Comparando as situações, não houve diferenças significativas entre as mesmas para RF, BF e TA, exceto para o músculo GLque obteve menores valores de ativação para a situação RE comparada à SE. Para os resultados de FRS, foram encontrados maiores valores para a intensidade MAX para as situações SE e RE, enquanto para FL, não foram encontradas diferenças de FRS entre as intensidades. Comparando as situações, FL obteve menores valores comparado à SE e RE, nas duas intensidades. Para os resultados de impulso (IMP), foram encontradas diferenças significavamente menores para a intensidade MAX para todas as situações, com menores valores de IMP na situação FL. A partir dos resultados encontrados no 6 presente estudo, de uma maneira geral, a utilização de equipamentos tanto RE quanto FL, parece não influenciar a ativação muscular durante a execução do exercício CH, além disso, a intensidade MAX elicita maiores valores de ativação. Além disso, apesar de terem sido encontradas diferenças de FRS e IMP entre as intensidades, o equipamento FL obteve menores valores de FRS e IMP, sem diferenças entre LV2 e MAX na FRS, demonstrando que apesar de obter uma maior ativação muscular em MAX, não houve um aumento significativo de FRS nesta intensidade. Sendo assim, a utilização de equipamentos parece influenciar principalmente a variável de FRS, reduzindo estes valores e tornando o exercício de CH mais seguro quando é necessária uma menor sobrecarga articular, enquanto a ativação muscular não se difere das outras situações. / The aim of the presente study was to analyze the muscle activation and ground reaction forces responses of one hydrogymnastic exercise performed by women with different devices. Three sessions of water progressive testes were conducted with 48 hours of interval with the frontal kick exercise (FK) without devices (WD), with resistance devices (RD) and floating devices (FD), to determine the cadence corresponding to the second ventilatory threshold (VT2).The third and last day of tests consisted iniciated with the maximum voluntary contraction (MVC) of the muscles to be analyzed: rectus femoris (RF), biceps femoris (BF), tibialis anterior (TA) and gastrocnemius lateralis (GL). After that, the electrodes were isolated and than the subject entered the pool (immersion on the xifoide process) to perform the electromiography (EMG) and ground reaction forces (GRF) tests in VT2 and maximum (MAX) intensity. Generalized estimating equation and Bonferroni’s test were used for the statistical analyses. The results showed higher muscle activity for the MAX comparing to VT2 for RF, BF and TA, except for GL muscle, which didn’t achieve difference between the intensities for RD. Comparing the three situations, there was no significant difference between. In VT2 and MAX there was no difference between all situations, except for GL in MAX, which obtained lower values for RD compared with FD. The ground reaction forces results showed higher values for the MAX intensity for the WD and RD situations, while for FD there was no difference between VT2 and MAX. Comparing the situations, FD obtained lower values compared with WD and RD in both intensities. For impulse (IMP), significant lower values were founde for the MAX intensity for all situations, with lower values for FD. According to the results, it might be concluded that the use of devices seems to not influence the muscle activity during the FK exercise, besides that, the MAX intensity elicits higher results. Despite the differences for GRF and IMP, the FL situation leads to a higher muscle activation in MAX while there is no GRF increase from VT2. Therefore, the use of devices appears to influence mostly the GRF variable, showing lowest values for this situation comparing to WD and RD making FK safer when a lower joint overload is needed, while the muscle activation didn’t differ from WD and RD.

O objetivo do presente estudo foi de analisar as respostas de ativação muscular e força de reação do solo de um exercício de hidroginástica com diferentes equipamentos, executado por mulheres jovens. Sendo assim, foram realizados três testes progressivos máximos em ambiente aquático, com no mínimo 48 horas de intervalo, com o exercício de chute, sem equipamento (SE), com equipamento resistivo (RE) e flutuante (FL), a fim de determinar a cadência correspondente ao segundo limiar ventilatório (LV2). O terceiro e último dia de testes consistiu primeiramente na contração voluntária isométrica máxima (CVM) em ambiente terrestre, dos músculos a serem avaliados: reto femoral (RF), bíceps femoral (BF), tibial anterior (TA) e gastrocnêmio lateral (GA). Após finalizada a CVM de cada músculo, foi feito um isolamento dos eletrodos, e então o sujeito entrou na piscina para realizar os testes de eletromiografia (EMG) e força de reação do solo (FRS) nas intensidades do LV2 e máximo esforço (MAX). Dentro da piscina, o sujeito foi posicionado na profundidade do processo xifóide e então, executou as três situações do exercício de chute (SE, RE e FL), de forma randomizada, nas intensidades LV2 e máximo esforço (MAX). Foi utilizada o teste estatístico de Equações estimativas generalizadas e o teste post-hoc de Bonferroni. Após o tratamento dos dados e análise estatística, foram encontrados maiores valores de ativação muscular da intensidade LV2 para MAX, para todas as situações nos músculos RF, BF e TA, exceto para GL que não obteve diferenças entre intensidades para a situação RE. Comparando as situações, não houve diferenças significativas entre as mesmas para RF, BF e TA, exceto para o músculo GLque obteve menores valores de ativação para a situação RE comparada à SE. Para os resultados de FRS, foram encontrados maiores valores para a intensidade MAX para as situações SE e RE, enquanto para FL, não foram encontradas diferenças de FRS entre as intensidades. Comparando as situações, FL obteve menores valores comparado à SE e RE, nas duas intensidades. Para os resultados de impulso (IMP), foram encontradas diferenças significavamente menores para a intensidade MAX para todas as situações, com menores valores de IMP na situação FL. A partir dos resultados encontrados no 6 presente estudo, de uma maneira geral, a utilização de equipamentos tanto RE quanto FL, parece não influenciar a ativação muscular durante a execução do exercício CH, além disso, a intensidade MAX elicita maiores valores de ativação. Além disso, apesar de terem sido encontradas diferenças de FRS e IMP entre as intensidades, o equipamento FL obteve menores valores de FRS e IMP, sem diferenças entre LV2 e MAX na FRS, demonstrando que apesar de obter uma maior ativação muscular em MAX, não houve um aumento significativo de FRS nesta intensidade. Sendo assim, a utilização de equipamentos parece influenciar principalmente a variável de FRS, reduzindo estes valores e tornando o exercício de CH mais seguro quando é necessária uma menor sobrecarga articular, enquanto a ativação muscular não se difere das outras situações. / The aim of the presente study was to analyze the muscle activation and ground reaction forces responses of one hydrogymnastic exercise performed by women with different devices. Three sessions of water progressive testes were conducted with 48 hours of interval with the frontal kick exercise (FK) without devices (WD), with resistance devices (RD) and floating devices (FD), to determine the cadence corresponding to the second ventilatory threshold (VT2).The third and last day of tests consisted iniciated with the maximum voluntary contraction (MVC) of the muscles to be analyzed: rectus femoris (RF), biceps femoris (BF), tibialis anterior (TA) and gastrocnemius lateralis (GL). After that, the electrodes were isolated and than the subject entered the pool (immersion on the xifoide process) to perform the electromiography (EMG) and ground reaction forces (GRF) tests in VT2 and maximum (MAX) intensity. Generalized estimating equation and Bonferroni’s test were used for the statistical analyses. The results showed higher muscle activity for the MAX comparing to VT2 for RF, BF and TA, except for GL muscle, which didn’t achieve difference between the intensities for RD. Comparing the three situations, there was no significant difference between. In VT2 and MAX there was no difference between all situations, except for GL in MAX, which obtained lower values for RD compared with FD. The ground reaction forces results showed higher values for the MAX intensity for the WD and RD situations, while for FD there was no difference between VT2 and MAX. Comparing the situations, FD obtained lower values compared with WD and RD in both intensities. For impulse (IMP), significant lower values were founde for the MAX intensity for all situations, with lower values for FD. According to the results, it might be concluded that the use of devices seems to not influence the muscle activity during the FK exercise, besides that, the MAX intensity elicits higher results. Despite the differences for GRF and IMP, the FL situation leads to a higher muscle activation in MAX while there is no GRF increase from VT2. Therefore, the use of devices appears to influence mostly the GRF variable, showing lowest values for this situation comparing to WD and RD making FK safer when a lower joint overload is needed, while the muscle activation didn’t differ from WD and RD.

The purpose of this study was to examine the effects of vertically oriented resistance training on golf driving performance. Ten Division-I collegiate golfers completed two resistance training sessions per week for 10 weeks during the fall tournament season. Pre- and post-training assessments of strength-power and golf performance were compared. To assess strength-power, jump height, peak force, and peak power were measured from static and countermovement vertical jumps; peak force and rate of force development from 0 to 250 ms were measured from an isometric mid-thigh pull. Golf performance was assessed in terms of ball launch speed, spin rate, carry yardage, and total yardage, averaged from five shots using a driver. Following training, all measures of strength-power improved, with countermovement jump peak power improving significantly (p < 0.00625). The golf performance assessment indicated significant increases (p < 0.0125) in ball speed, carry yardage, and total yardage. These results suggest that vertically oriented resistance training can improve golf driving performance.

Yoga adherents claim many benefits of the practice, including promotion of bone health and prevention of osteoporosis. However, few, if any, studies have investigated whether yoga enhances bone mineral density. Furthermore, none have identified force generation in yoga. The purpose of this study is to collect ground reaction force (GRF) data on a variety of common hatha yoga postures that would be practiced in fitness centers or private studios. Twelve female and eight male volunteers performed a sequence of 28 common hatha yoga postures while ground reaction force data were collected with an AMTI strain-gauge force plate. The sequence was repeated six times. Four variables were studied: the maximum vertical GRF, the mean vertical GRF, the maximum resultant GRF, and the mean resultant GRF. Univariate analysis was used to identify mean values and standard deviations for each of the four variables. Multivariate analysis revealed some variation due to gender but none due to age or weight. Means were similar across all poses and subjects, and standard deviations were small. This unique yoga sequence produced low impact forces in both upper and lower extremities. Further research is warranted to determine whether these forces are sufficient to promote osteogenesis or maintain current bone health in yoga practitioners.

The purpose of this study was to compare joint moments during the active peak vertical ground reaction force (PVGRF) when running in three conditions. Twenty-five subjects, sixteen male and nine female, were measured using 3-dimensional motion analysis while running barefoot, in Vibram FiveFingers® (VF®) minimalist running shoes and in traditional running shoes at a 7-minute-mile pace (3.84 m/s). Joint moment differences were calculated and compared using a mixed model analysis of variance. Results showed the VF® was effective at mimicking both the kinetic and kinematic attributes of barefoot running. The only significant difference found when comparing barefoot and VF® running was in the ankle angle (p < .005). All other variables in the lower extremity were the same for the two conditions. Though the subjects in our study had no previous experience with VF® (or barefoot) running they were able to closely mimic barefoot running upon initial running trials. Joint moments at the ankle were higher for barefoot and VF® running (p < .001) when compared with shod running. This may potentially lead to a greater risk of injury at the ankle joint when running barefoot or in VF®. The hip joint moments were only different when comparing the barefoot condition to the shod condition (p=.002), with the barefoot condition higher than shod running. The knee joint moment was smaller during the VF® and barefoot conditions when compared with shod running (p < .001) and may lead to a decrease in injury rates at the knee. Though a reduction in moments of the lower extremity may lead to a decrease of injury at the corresponding joint, it is important to consider the adaptations that take place as a result of varying stresses. According to Wolff's law, bone and surrounding tissue will adapt to the loads it is placed under. Taking this into consideration, it is important to remember that lower moments may lead to weaker bones and surrounding tissues and without compensation for these reduced loads, injury rates may remain the same over time.

ABSTRACT Effect of Warm-Up Activity on Vertical Ground Reaction Forces in Basketball Players During Drop Jump Landings Jacob Hinkel-Lipsker Purpose: The purpose of this study was to examine the effect of certain warm-up activities on vertical ground reaction forces (GRFv) during a drop jump landing. Methods: Eight women and twelve men (mean age 22.6 ± 1.82 years) completed three warm-up activities on three separate days in a counterbalanced order: a passive stretching warm-up, a dynamic warm-up, and a no warm-up control. After completing each activity, participants were asked to perform eight drop jump landings on a force platform. GRFv data was sampled at 1000 Hz during each landing, and the variables analyzed were: peak forefoot and rearfoot magnitude, forefoot and rearfoot rate of loading, and impulse. Results: The dynamic warm-up had significantly greater values (p < 0.05) for forefoot peak magnitude, rearfoot peak magnitude, and forefoot rate of loading compared to the passive stretching and control conditions. Also, there were no significant differences among all activities for rearfoot rate of loading and impulse. Conclusions: The significantly greater values for forefoot peak magnitude, rearfoot peak magnitude, and forefoot rate of loading that the dynamic warm-up produced indicates that this activity may be effective in increasing muscular stiffness in the lower limbs. The failure of the passive stretching warm-up to reach significance indicates that this activity may not be effective in decreasing lower extremity muscular stiffness.

The analysis of human movement is important for diagnosis of as wellas planning and evaluating treatments of disorders or injuries affectingmovement. Optical motion capture combined with force plates provideaccurate measurements, but are confined to laboratory settings limiting theirpotential usefulness in clinical applications. Efforts are made to movemeasurements out of the laboratory making them more accessible, cheaperand easier to use for healthcare providers. This work aimed to assess thefeasibility of doing motion analysis with a wearable system consisting ofIMUs and pressure insole sensors, while also developing a methodology thatcould be used for subsequent validation. Six subjects performed walking, sideskipping, squats, chair stands and a balance exercise, while data was collectedsimultaneously from the wearable system and optical motion capture withforce plates. For demonstration, data from one example subject was analysedand included in this work. The wearable system showed promising results formeasuring ground reaction force. Center of pressure errors were relativelyhigh, likely influenced by the choice of method for coordinate transformationbetween the systems. Joint angle errors varied from low to very high fordifferent trials. Ankle dorsiflexion angle showed low errors and pelvis tiltangle high errors for all motion types. There is a need to investigate thecause for these high errors before more measurements are conducted. Themethodology presented in this work can, with a few recommended changes,be used for future validation of the wearable motion analysis system.

Inledning: Löpning är en effektiv träningsform som blir alltmer populär, tyvärr är skaderisken relativ hög med en incidens på 37% per år. Låg stegfrekvens samt en hög vertical ground reaction force, vGRF, vilket betyder den vertikala kraften kroppen utsätts för i fotisättningen är associerad med en ökad skaderisk. Löpstegskorrigering används idag som en behandlingsintervention vid löprelaterade skador och det råder idag konsensus i forskningen om att olika typer av muntliga instruktioner är ett effektivt sätt att korrigera löpteknik för att minska skaderisken. Syfte: Syftet med studien var att undersöka två olika instruktioner för löpstegskorrigering hos unga kvinnor. Metod: Sex kvinnliga löpare fick springa på löpband med kraftmätningssulor på sig och erhålla de två olika instruktionerna “Spring tyst” samt “Sträck på dig och försök att inte böja i höften” där kadens och kraftisättning jämfördes mellan de båda instruktionerna. Resultat: Resultatet visade inte på någon förändring gällande kadens för någon av instruktionerna. Gällande kraftimpuls sågs en ökning av kraft vid instruktionen “Sträck på dig och försök att inte böja i höften” och en marginell minskning i kraftimpuls vid instruktionen “Spring tyst”. Konklusion: Ingen av instruktionerna visade sig vara effektiva för att minska vGRF eller öka kadens. Den minskning som sågs i vGRF med instruktionen ”Spring tyst” är för liten för att dra någon slutsats från och mer forskning krävs därför på området. Med förslag på justeringar skulle studieupplägget från denna pilotstudie kunna fungera för en fullskalig studie.

Formål: Formålet med studiet er at undersøge hvordan løb med en dagligdagsprotese og en løbespecifikprotese påvirker kinetik i nedre ekstremiteter hos mennesker med en transtibial-amputation.   Metode: Kinetisk data blev indsamlet ved løbetests, med begge proteser, med et motion capture system og kraftplader i et klinisk ganganalyse lab i Göteborg, Sverige. Deltagere(n=2) udførte løbetests i selvvalgt hastighed, iført refleksive markører. Vertikal GRF, fod progressions vinkel, adducerende/abducerende hofte- og knæmoment udvalgt til videre databehandling.   Resultat: Forskelle i hofte- og knæ adduktions moment og fod progressions vinkel blev observeret mellem de to protesetyper. Momenterne var mindre, når deltagerne løb med den løbespecifikke protese. Forskelle på den amputerede side og den kontralaterale side noteredes ved alle parametre uanset protesetype. Den kontralaterale side havde forøgede værdier sammenlignet med den amputerede side.   Konklusion: Grundet forsøgets størrelse kan vi ikke konkludere, at individer med unilateral amputation i nedre ekstremitet absorberer belastning bedre, når de løber med en løbespecifikprotese fremfor en dagligdagsprotese. / Aim: The aim of this study was to investigate how running with a daily-use prosthesis and a running specific prosthesis affects kinetics in the lower extremities when it comes to people with a transtibial amputation.   Method: Kinetic data was collected through running tests, using both type of prosthesis, with a motion capture system and force plates in a clinical gait lab in Gothenburg, Sweden. Participants (n=2) executed the running tests in a self-selected speed, while wearing reflective markers. Vertical ground reaction force, foot progression angle, hip- and knee moment were selected for data processing.   Results: Differences in hip- and knee adduction moment and foot progression angle were observed between the two types of prostheses. Moments were smaller when participants ran with running-specific prosthesis. Dissimilarity for the amputated side and the contralateral side were noted for all parameters regardless of type of prosthesis. The contralateral side had increased values compared to the amputated side.     Conclusion: Because of the sample size we cannot conclude that individuals with a unilateral lower body amputation absorb load more efficiently when running with a running-specific prosthesis rather than a daily-use prosthesis.