scholarly journals Optimum take-off techniques and muscle design for long jump

2000 ◽  
Vol 203 (4) ◽  
pp. 741-750 ◽  
Author(s):  
A. Seyfarth ◽  
R. Blickhan ◽  
J.L. Van Leeuwen
Keyword(s):  
Mechanical Energy ◽  
Relative Length ◽  
Maximum Speed ◽  
Force Enhancement ◽  
Muscle Properties ◽  
Cross Sectional ◽  
Extensor Muscles ◽  
Long Jump ◽  
Work Done ◽  
Tendon Properties

A two-segment model based on Alexander (1990; Phil. Trans. R. Soc. Lond. B 329, 3–10) was used to investigate the action of knee extensor muscles during long jumps. A more realistic representation of the muscle and tendon properties than implemented previously was necessary to demonstrate the advantages of eccentric force enhancement and non-linear tendon properties. During the take-off phase of the long jump, highly stretched leg extensor muscles are able to generate the required vertical momentum. Thereby, serially arranged elastic structures may increase the duration of muscle lengthening and dissipative operation, resulting in an enhanced force generation of the muscle-tendon complex. To obtain maximum performance, athletes run at maximum speed and have a net loss in mechanical energy during the take-off phase. The positive work done by the concentrically operating muscle is clearly less than the work done by the surrounding system on the muscle during the eccentric phase. Jumping performance was insensitive to changes in tendon compliance and muscle speed, but was greatly influenced by muscle strength and eccentric force enhancement. In agreement with a variety of experimental jumping performances, the optimal jumping technique (angle of attack) was insensitive to the approach speed and to muscle properties (muscle mass, the ratio of muscle fibre to tendon cross-sectional area, relative length of fibres and tendon). The muscle properties also restrict the predicted range of the angle of the velocity vector at take-off.

Mechanical power and work of cat soleus, gastrocnemius and plantaris muscles during locomotion: possible functional significance of muscle design and force patterns.

1996 ◽  
Vol 199 (4) ◽  
pp. 801-814 ◽  
Author(s):  
B I Prilutsky ◽  
W Herzog ◽  
T L Allinger
Keyword(s):  
Electrical Activity ◽  
Mechanical Energy ◽  
Fibre Length ◽  
Rate Of Change ◽  
The Body ◽  
Mechanical Power ◽  
Step Cycle ◽  
Extensor Muscles ◽  
Work Done ◽  
Positive Work

Electrical activity, forces, power and work of the soleus (SO), the gastrocnemius (GA) and the plantaris (PL) muscles were measured during locomotion in the cat in order to study the functional role of these ankle extensor muscles. Forces and electrical activity (EMG) of the three muscles were measured using home-made force transducers and bipolar, indwelling wire electrodes, respectively, for walking and trotting at speeds of 0.4 to 1.8 m s-1 on a motor-driven treadmill. Video records and a geometrical model of the cat hindlimb were used for calculating the rates of change in lengths of the SO, GA and PL muscles. The instantaneous maximum possible force that can be produced by a muscle at a given fibre length and the rate of change in fibre length (termed contractile abilities) were estimated for each muscle throughout the step cycle. Fibre lengths of the SO, GA and PL were calculated using a planar, geometrical muscle model, measured muscle forces and kinematics, and morphological measurements from the animal after it had been killed. Mechanical power and work of SO, GA and PL were calculated for 144 step cycles. The contribution of the positive work done by the ankle extensor muscles of one hindlimb to the increase of the total mechanical energy of the body (estimated from values in the literature) increased from 4-11% at speeds of locomotion of 0.4 and 0.8 m s-1 to 7-16% at speeds of 1.2 m s-1 and above. The relative contributions of the negative and positive work to the total negative and positive work done by the three ankle extensor muscles increased for GA, decreased for SO and remained about the same for PL, with increasing speeds of locomotion. At speeds of 0.4-0.8 m s-1, the positive work normalized to muscle mass was 7.5-11.0 J kg-1, 1.9-3.0 J kg-1 and 5.3-8.4 J kg-1 for SO, GA and PL, respectively. At speeds of 1.2-1.8 m s-1, the corresponding values were 9.8-16.7 J kg-1, 6.0-10.7 J kg-1 and 13.4-25.0 J kg-1. Peak forces of GA and PL increased and peak forces of SO did not change substantially with increasing speeds of locomotion. The time of decrease of force and the time of decrease of power after peak values had been achieved were much shorter for SO than the corresponding times for GA and PL at fast speeds of locomotion. The faster decrease in the force and power of SO compared with GA and PL was caused by the fast decrease of the contractile abilities and the activation of SO. The results of this study suggest that the ankle extensor muscles play a significant role in the generation of mechanical energy for locomotion.

scholarly journals Stakeholders’ perceptions of the nutrition and dietetics needs and the requisite professional competencies in Uganda: a cross-sectional mixed methods study

2021 ◽  
Vol 21 (1) ◽  
Author(s):  
Peterson Kato Kikomeko ◽  
Sophie Ochola ◽  
Archileo N. Kaaya ◽  
Irene Ogada ◽  
Tracy Lukiya Birungi ◽  
...  
Keyword(s):  
Mixed Methods ◽  
Academic Staff ◽  
Human Nutrition ◽  
Cross Sectional ◽  
Knowledge And Skills ◽  
Bachelor's Degrees ◽  
Competency Based ◽  
Health Systems Performance ◽  
Nutrition And Dietetics ◽  
Work Done

Abstract Background Effective implementation of nutrition and dietetics interventions necessitates professionals in these fields to possess the requisite competencies for health systems performance. This study explored the stakeholders’ perceptions of the community nutrition and dietetics needs, the nature of work done by graduates of the Bachelor’s degree in Human Nutrition/Human Nutrition and Dietetics (HN/HND), and the competencies required of Nutrition and Dietetics professionals in Uganda. Methods A cross-sectional mixed methods design was used. Respondents included 132 graduates of the Bachelor’s degrees in HN/HND obtained from the Makerere and Kyambogo Universities in 2005–2016; 14 academic staff that train HN/HND in the two universities; and 11 HN/HND work/internship supervisors. Data from the graduates was collected through an email-based survey; data from other participants was through face to face interviews using researcher administered questionnaires. Results Most HN/HND respondents (84.8%) obtained their Bachelor’s degrees from Kyambogo University; 61.4% graduated in 2013–2016. Most (64.3%) academic staff respondents were females and the majority (57.1%) had doctorate training. All stakeholders viewed communities as facing a variety of nutrition and dietetics challenges cutting across different Sustainable Development Goals. The nutrition and dietetics interventions requested for, provided, and considered a priority for communities were both nutrition-specific and nutrition-sensitive. Work done by HN/HND graduates encompassed seven main competency domains; the dominant being organizational leadership and management; management of nutrition-related disease conditions; nutrition and health promotion; research; and advocacy, communication, and awareness creation. Conclusions This study shows that nutrition and dietetics challenges in Uganda are multiple and multifaceted; HN/HND graduates are employed in different sectors, provide nutrition-specific and sensitive services in a multisectoral environment, and are expected to possess a variety of knowledge and skills. However, graduates have knowledge and skills gaps in some of the areas they are expected to exhibit competency. We recommend using these findings as a basis for obtaining stakeholder consensus on the key competencies that should be exhibited by all HN/HND graduates in Uganda; developing a HN/HND competency-based education model and a national HN/HND training and practice standard; and undertaking further research to understand the quality and relevancy of HN/HND curricula to Uganda’s job market requirements.

The Preoperative Cross-sectional Area of the Deep Cervical Extensor Muscles Does Not Predict Loss of Lordosis After Cervical Laminoplasty

2021 ◽  
Vol Publish Ahead of Print ◽  
Author(s):  
Jinping Liu ◽  
Rong Xie ◽  
Huibing Ruan ◽  
Joshua Rivera ◽  
Bo Li ◽  
...  
Keyword(s):  
Cross Sectional Area ◽  
Cervical Laminoplasty ◽  
Sectional Area ◽  
Cross Sectional ◽  
Extensor Muscles

Weak psoas and spine extensors potentially predispose to hip fracture

2020 ◽  
pp. 112070002090433
Author(s):  
Keong-Hwan Kim ◽  
Jun Hee Lee ◽  
Eic Ju Lim
Keyword(s):  
Hip Fracture ◽  
Lumbar Vertebra ◽  
Psoas Muscle ◽  
Hounsfield Unit ◽  
The Body ◽  
Whole Body ◽  
Cross Sectional ◽  
Fracture Group ◽  
Extensor Muscles ◽  
Significant Difference

Introduction: We performed a computed tomography analysis of muscle composition characteristics in hip fracture patients and non-hip fracture controls. Methods: In total, 43 patients (9 men, 34 women) were included in the hip fracture group, matched 1 to 1 with non-hip fracture controls. Muscle cross-sectional areas were measured in axial CT scan at the body level of the 4th lumbar vertebra (L4), intervertebral disc level between the 5th lumbar vertebra and the 1st sacral vertebra (L5-S1) and just below level of the lesser trochanter (LT). Attenuation was also evaluated through the mean Hounsfield unit (HU) in these areas. Results: The cross-sectional area per weight (CSA/Wt, mm2/kg) of psoas muscle and extensor muscles of the spine showed a significant difference between the 2 groups at both L4 (9.7 vs. 12.4, p  < 0.001 and 26.3 vs. 29.2, p  = 0.025) and L5-S1 (9.6 vs. 11.5, p  = 0.001 and 8.8 vs. 10.3, p  = 0.041) levels. In addition, the HU of these muscles differed significantly between the 2 groups at both L4 (33.3 vs. 47.6, p  < 0.001 and 13.7 vs. 30.2, p  < 0.001) and L5-S1 (39.7 vs. 52.6, p  < 0.001 and 3.8 vs. 15.1, p  = 0.012) levels. There was no difference in abdominal wall, gluteal, or thigh compartment musculature between the groups. Conclusions: Poorer quantity and quality of psoas muscle and extensor muscles of the spine rather than whole body muscles may contribute to falls and were characteristic features of the hip fracture patients in this series. These findings should be considered when recommending a preventive exercise and rehabilitation protocol.

Cross-sectional area and mean echogenicity of shoulder and elbow tendons in adult German Shepherd dogs

2013 ◽  
Vol 26 (05) ◽  
pp. 366-371 ◽  
Author(s):  
G. Loprete ◽  
V. Musella ◽  
D. Britti ◽  
J. M. Vilar ◽  
G. Spinella
Keyword(s):  
Cross Sectional Area ◽  
Sectional Area ◽  
Triceps Brachii ◽  
German Shepherd ◽  
Cross Sectional ◽  
Extensor Muscles ◽  
Flexor Carpi Ulnaris ◽  
Triceps Brachii Muscle ◽  
The Cross ◽  
Distal Tendon

SummaryThe aim of this study was to describe the cross-sectional area and mean echogenicity of the main tendons of the shoulder and elbow joints in adult German Shepherd dogs and to determine the effects of sex, weight, and age on these parameters. No previous publications in the veterinary literature have reported information regarding quantitative ultrasonographic tendon measurements in dogs.Thirty German Shepherd dogs were examined: 13 males and 17 females. The cross-sectional area was significantly higher in males than in females (p <0.05) for the distal tendon of the triceps brachii muscle and the tendons of the flexor carpi ulnaris and common digital extensor muscles. The influence of sex on mean echogenicity was not significant. According to age, mean echogenicity was higher in older dogs, while the cross-sectional areas were similar in the two groups. Cross-sectional area and mean echogenicity of the tendons showed a direct increase with an increase in body weight. The data gained from this study can help support the clinician to discriminate between normal and pathological conditions.

scholarly journals Analysis of dynamics of a vertical cantilever in rotary coupling to the moving frame with movement limiters

2018 ◽  
Vol 241 ◽  
pp. 01021
Author(s):  
Piotr Wolszczak ◽  
Grzegorz Litak ◽  
Krystian Lygas
Keyword(s):  
Mechanical Energy ◽  
Elastic Beam ◽  
Beam Deflection ◽  
Moving Frame ◽  
Nonlinear Phenomena ◽  
Horizontal Distance ◽  
Energy Effect ◽  
Cross Sectional ◽  
Excitation Beam ◽  
Analysis Of Dynamics

The efficiency of the mechanical energy harvesting with the use of vibrating elements can be improved by synchronizing stimulation vibrations and own linear frequencies of systems as well as super or sub harmonics induced by non-linear phenomena. The article presents numerical cross-sectional study of the mechanical system. The system consists of an elastic beam set vertically, which the lower end is fixed in the rotary support, and is stimulated to move in the horizontal axis. The upper end of the beam is free but below its level there are bumpers limiting the free rotation of the beam. Numerical studies took into account the variability of the frequency and amplitude of the excitation beam movement, and horizontal distance between bumpers. Beam deflection was observed, on the basis of which the amount of energy generated by the piezo element was estimated. Nonlinear phenomena and analysis of frequency synchronization of vibrations improving the energy effect of an energy generator are presented.

scholarly journals Relationship between Ratio of Second and Fourth Digit and Obesity Traits among Different Ethnic Groups in Ilorin, North Central Nigeria

2016 ◽  
Vol 8 (4) ◽  
pp. 396-400 ◽  
Author(s):  
Bolaji Fatai OYEYEMI ◽  
John Oluwafemi ADEBAYO ◽  
Abass Toba ANIFOWOSHE ◽  
Oluyinka Ajibola IYIOLA
Keyword(s):  
Ethnic Groups ◽  
Pearson Correlation ◽  
Standard Procedure ◽  
Surrogate Marker ◽  
Relative Length ◽  
Cross Sectional Study ◽  
Digit Ratio ◽  
Sectional Study ◽  
Cross Sectional ◽  
Significant Difference

Digit ratio (2D:4D) denotes the relative length of the second and fourth digits. There are contradicting reports on its relationship with ethnicity/race, whereas convincing studies show it is related to obesity. This cross-sectional study was undertaken to demystify ethnic difference in 2D:4D ratio and to analyze its relationship with obesity among adults in Ilorin Nigeria. The cross-sectional study included 701 individuals. Finger lengths were measured with electronic calipers and other anthropometric traits were measured with standard procedure. Student t test and one-way ANOVA were used to detect differences among groups and relationship was computed with Pearson correlation. The receiver operator characteristic curves were used to detect the diagnostic effect of 2D:4D for obesity. The obtained results showed sexual dimorphism in 2D:4D ratio and other anthropometrics at p < 0.01. Obesity was associated with significantly higher mean of 2D:4D in both genders (female 0.9814 ± 0.012:0.9700 ± 0.012; male 0.9700 ± 0.010:0.9592 ± 0.010 at p < 0.001). The area under the curve was 0.753 (95% CI 0.677-0.829, p < 0.01) and 0.798 (95% CI 0.756-0.804, p < 0.01) in female and male R2D:4D respectively for obesity, implying that 2D:4D might be a surrogate marker for obesity in future.  No significant difference was found in 2D:4D among different ethnic groups studied (p >0.05); this result proved that there was no ethnic specificity in 2D:4D ratio among study’ participants. Thus, it can be reported that the digit ratio was related to high 2D:4D, but this cannot be said for different ethnic groups. The results imply that 2D:4D might be a good surrogate indicator for obesity, but not ethnicity.  

scholarly journals Changes in Cross-sectional Areas of Posterior Extensor Muscles in Thoracic Spine: A 10-year Longitudinal MRI Study

2021 ◽  
Author(s):  
Hitoshi Umezawa ◽  
Kenshi Daimon ◽  
Hirokazu Fujiwara ◽  
Yuji Nishiwaki ◽  
Takehiro Michikawa ◽  
...  
Keyword(s):  
Cross Section ◽  
Disc Degeneration ◽  
Thoracic Spine ◽  
Erector Spinae ◽  
Related Factors ◽  
Cross Sectional ◽  
Fat Infiltration ◽  
Extensor Muscles ◽  
The Cross ◽  
Muscle Fat Infiltration

Abstract This study aimed to examine changes in the cross-sectional areas (CSAs) of posterior extensor muscles in the thoracic spine over 10 years and identify related factors. The subjects of this study were 85 volunteers (mean age: 44.8 ± 11.5) and the average follow-up period was about 10 years. The CSAs of the transversospinalis muscles, erector spinae muscles, and total CSAs of the extensor muscles from T1/2 to T11/12 were measured on MRI. The extent of muscle fat infiltration was assessed by the signal intensity (luminance) of the extensor muscles’ total cross section compared to a section of pure muscle. Associations of age, sex, body mass index, lifestyle, back pain, neck pain, neck stiffness, and intervertebral disc degeneration with the 10-year CSAs changes and muscle fat infiltration were examined by Poisson regression analysis. The mean CSAs of all index muscles increased significantly. Exercise habit was associated with increased CSAs of the erector spinae muscles and the total area of the extensor muscles. The cross-section mean luminance increased significantly from baseline, indicating a significant increase of fat infiltration in the posterior extensor muscles. Progression of disc degeneration was negatively associated with the increase of fat infiltration in the total extensor muscles.

Distensibility of the Left Atrial Wall in Spontaneously Hypertensive Rats Compared with That in Normotensive Wistar-Kyoto Rats

1980 ◽  
Vol 59 (s6) ◽  
pp. 361s-363s
Author(s):  
S.-E. Ricksten ◽  
T. Yao ◽  
B. Ljung ◽  
P. Thorean
Keyword(s):  
Left Atrial ◽  
Spontaneously Hypertensive Rats ◽  
Relative Length ◽  
Hypertensive Rats ◽  
Atrial Wall ◽  
Cross Sectional ◽  
Spontaneously Hypertensive ◽  
Wistar Kyoto Rats ◽  
Left Atrial Wall ◽  
Wistar Kyoto

1. The cardiac mechanoreceptors, which in rats are mainly located in the left atrial wall, are reset in spontaneously hypertensive rats. The atrial pressure has to be almost twice as high in spontaneously hypertensive rats as in normotensive controls to produce similar receptor activations, as is apparent from previous studies. 2. The present study was performed to investigate whether this resetting is due to decreased distensibility of left atrial walls in the spontaneously hypertensive rats. 3. Static load-length relationships were investigated in vitro on left atrial strips, and pressure-volume relationships were studied on isolated left atria from spontaneously hypertensive and normotensive Wistar-Kyoto rats. 4. The force per cross-sectional area exerted during a relative length increase of 80% was significantly greater in spontaneously hypertensive rats. The dynamic but not the static distensibility was significantly lower in these animals. 5. The decreased dynamic distensibility of left atrial walls in spontaneously hypertensive rats can at least partly explain the resetting of atrial receptor function.

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