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1Latest Papers from Table of Contents or Articles in PressP. M. Sarte, A. M. Arévalo-López, M. Songvilay, D. Le, T. Guidi, V. García-Sakai, S. Mukhopadhyay, S. C. Capelli, W. D. Ratcliff, K. H. Hong, G. M. McNally, E. Pachoud, J. P. Attfield, and C. Stock
American Physical Society (APS)
Published 2018Staff ViewPublication Date: 2018-12-07Publisher: American Physical Society (APS)Print ISSN: 1098-0121Electronic ISSN: 1095-3795Topics: PhysicsKeywords: MagnetismPublished by: -
2Latest Papers from Table of Contents or Articles in PressI. Lazaridis ; N. Patterson ; A. Mittnik ; G. Renaud ; S. Mallick ; K. Kirsanow ; P. H. Sudmant ; J. G. Schraiber ; S. Castellano ; M. Lipson ; B. Berger ; C. Economou ; R. Bollongino ; Q. Fu ; K. I. Bos ; S. Nordenfelt ; H. Li ; C. de Filippo ; K. Prufer ; S. Sawyer ; C. Posth ; W. Haak ; F. Hallgren ; E. Fornander ; N. Rohland ; D. Delsate ; M. Francken ; J. M. Guinet ; J. Wahl ; G. Ayodo ; H. A. Babiker ; G. Bailliet ; E. Balanovska ; O. Balanovsky ; R. Barrantes ; G. Bedoya ; H. Ben-Ami ; J. Bene ; F. Berrada ; C. M. Bravi ; F. Brisighelli ; G. B. Busby ; F. Cali ; M. Churnosov ; D. E. Cole ; D. Corach ; L. Damba ; G. van Driem ; S. Dryomov ; J. M. Dugoujon ; S. A. Fedorova ; I. Gallego Romero ; M. Gubina ; M. Hammer ; B. M. Henn ; T. Hervig ; U. Hodoglugil ; A. R. Jha ; S. Karachanak-Yankova ; R. Khusainova ; E. Khusnutdinova ; R. Kittles ; T. Kivisild ; W. Klitz ; V. Kucinskas ; A. Kushniarevich ; L. Laredj ; S. Litvinov ; T. Loukidis ; R. W. Mahley ; B. Melegh ; E. Metspalu ; J. Molina ; J. Mountain ; K. Nakkalajarvi ; D. Nesheva ; T. Nyambo ; L. Osipova ; J. Parik ; F. Platonov ; O. Posukh ; V. Romano ; F. Rothhammer ; I. Rudan ; R. Ruizbakiev ; H. Sahakyan ; A. Sajantila ; A. Salas ; E. B. Starikovskaya ; A. Tarekegn ; D. Toncheva ; S. Turdikulova ; I. Uktveryte ; O. Utevska ; R. Vasquez ; M. Villena ; M. Voevoda ; C. A. Winkler ; L. Yepiskoposyan ; P. Zalloua ; T. Zemunik ; A. Cooper ; C. Capelli ; M. G. Thomas ; A. Ruiz-Linares ; S. A. Tishkoff ; L. Singh ; K. Thangaraj ; R. Villems ; D. Comas ; R. Sukernik ; M. Metspalu ; M. Meyer ; E. E. Eichler ; J. Burger ; M. Slatkin ; S. Paabo ; J. Kelso ; D. Reich ; J. Krause
Nature Publishing Group (NPG)
Published 2014Staff ViewPublication Date: 2014-09-19Publisher: Nature Publishing Group (NPG)Print ISSN: 0028-0836Electronic ISSN: 1476-4687Topics: BiologyChemistry and PharmacologyMedicineNatural Sciences in GeneralPhysicsKeywords: Agriculture/history/manpower ; Asia/ethnology ; Europe ; European Continental Ancestry Group/*classification/*genetics ; Genome, Human/*genetics ; History, Ancient ; Humans ; Population Dynamics ; Principal Component AnalysisPublished by: -
3Latest Papers from Table of Contents or Articles in PressP. H. Sudmant ; S. Mallick ; B. J. Nelson ; F. Hormozdiari ; N. Krumm ; J. Huddleston ; B. P. Coe ; C. Baker ; S. Nordenfelt ; M. Bamshad ; L. B. Jorde ; O. L. Posukh ; H. Sahakyan ; W. S. Watkins ; L. Yepiskoposyan ; M. S. Abdullah ; C. M. Bravi ; C. Capelli ; T. Hervig ; J. T. Wee ; C. Tyler-Smith ; G. van Driem ; I. G. Romero ; A. R. Jha ; S. Karachanak-Yankova ; D. Toncheva ; D. Comas ; B. Henn ; T. Kivisild ; A. Ruiz-Linares ; A. Sajantila ; E. Metspalu ; J. Parik ; R. Villems ; E. B. Starikovskaya ; G. Ayodo ; C. M. Beall ; A. Di Rienzo ; M. F. Hammer ; R. Khusainova ; E. Khusnutdinova ; W. Klitz ; C. Winkler ; D. Labuda ; M. Metspalu ; S. A. Tishkoff ; S. Dryomov ; R. Sukernik ; N. Patterson ; D. Reich ; E. E. Eichler
American Association for the Advancement of Science (AAAS)
Published 2015Staff ViewPublication Date: 2015-08-08Publisher: American Association for the Advancement of Science (AAAS)Print ISSN: 0036-8075Electronic ISSN: 1095-9203Topics: BiologyChemistry and PharmacologyComputer ScienceMedicineNatural Sciences in GeneralPhysicsKeywords: African Continental Ancestry Group/classification/genetics ; Animals ; *DNA Copy Number Variations ; *Evolution, Molecular ; *Gene Duplication ; Genome, Human/*genetics ; Hominidae/genetics ; Humans ; Oceanic Ancestry Group/classification/genetics ; Phylogeny ; Polymorphism, Single Nucleotide ; Population/*genetics ; Selection, Genetic ; *Sequence DeletionPublished by: -
4Latest Papers from Table of Contents or Articles in PressS. R. Giblin, M. Twengström, L. Bovo, M. Ruminy, M. Bartkowiak, P. Manuel, J. C. Andresen, D. Prabhakaran, G. Balakrishnan, E. Pomjakushina, C. Paulsen, E. Lhotel, L. Keller, M. Frontzek, S. C. Capelli, O. Zaharko, P. A. McClarty, S. T. Bramwell, P. Henelius, and T. Fennell
American Physical Society (APS)
Published 2018Staff ViewPublication Date: 2018-08-08Publisher: American Physical Society (APS)Print ISSN: 0031-9007Electronic ISSN: 1079-7114Topics: PhysicsKeywords: Condensed Matter: Electronic Properties, etc.Published by: -
5Latest Papers from Table of Contents or Articles in PressG. Hellenthal ; G. B. Busby ; G. Band ; J. F. Wilson ; C. Capelli ; D. Falush ; S. Myers
American Association for the Advancement of Science (AAAS)
Published 2014Staff ViewPublication Date: 2014-02-18Publisher: American Association for the Advancement of Science (AAAS)Print ISSN: 0036-8075Electronic ISSN: 1095-9203Topics: BiologyChemistry and PharmacologyComputer ScienceMedicineNatural Sciences in GeneralPhysicsKeywords: Alleles ; Chromosome Painting/methods ; *Computer Simulation ; DNA/genetics ; Europe, Eastern/ethnology ; Genetic Drift ; *Genotyping Techniques ; Haplotypes ; History, Ancient ; Human Migration/*history ; Humans ; Middle East/ethnology ; *Models, Genetic ; Mongolia/ethnology ; Polymorphism, Single Nucleotide ; Population/*genetics ; SoftwarePublished by: -
6Articles: DFG German National LicensesZamparo, P. ; Antonutto, G. ; Capelli, C. ; Francescato, M. P. ; Girardis, M. ; Sangoi, R. ; Soule, R. G. ; Pendergast, D. R.
Oxford, UK : Blackwell Publishing Ltd
Published 1996Staff ViewISSN: 1600-0838Source: Blackwell Publishing Journal Backfiles 1879-2005Topics: MedicineSports ScienceNotes: Two forces act on a human body motionless in water: weight (W) and buoyancy (B). They are applied to the center of mass (CM) and to the center of volume (CV) of the subject, respectively. CM and CV do not coincide; this generates a torque that is a measure of the tendency of the upper part of the body to rise, rotating around its center of mass. To quantify this tendency, Pendergast & Craig defined ‘underwater torque’ (T1) as the product of the net force with which the feet of a subject lying horizontally in water tend to sink, times the distance between the feet and the center of volume of the lungs. In this paper we have investigated: (a) the relationships between T1 and body weight (BW), height (H), body surface area (BS), body density (BD) and leg density (LD) in a group of 30 subjects (group A, 14 females and 16 males, age range 16-50 years); and (b) the effect of gender and growth on T1 in a group of 110 subjects (group B, 67 girls and 43 boys, age range 12-17 years). In group A, T1 was found to be linearly related with BW (r= 0.833, P 〈 0.001), H (r= 0.803, P 〈 0.001), BS (r= 0.866, P 〈 0.001), BD (r= 0.617, P 〈 0.001) and LD (r= 0.549, P 〈 0.005). A multiple linear regression analysis showed that BS and BD explained about 85% of the variability of T1 (r2= 0.85). In group B, T1 was found to increase linearly with age (r= 0.47, P 〈 0.01), the increasing rate being three times higher in boys compared with girls. As a consequence, the T1 ratio between boys and girls increased with age, from 1.69 at 13 years to 2.04 at 16 years.Type of Medium: Electronic ResourceURL: -
7Articles: DFG German National LicensesCapelli, C. ; Donatelli, C. ; Moia, C. ; Valier, C. ; Rosa, G. ; Prampero, P. E.
Springer
Published 1990Staff ViewISSN: 1439-6327Keywords: Sculling ; Gondola ; Energy cost of locomotion ; Drag ; Efficiency of locomotionSource: Springer Online Journal Archives 1860-2000Topics: MedicineNotes: Summary Oxygen uptake was measured on four male subjects during sculling gondolas at constant speeds from ∼1 to ∼ 3 m · s−1. The number of scullers on board in the different trials was one, two or four. Tractional water resistance (drag,D, N) was also measured in the same range of speeds. Energy cost of locomotion per unit of distance (C, J·m−1), as calculated from the ratio of O2 uptake above resting to, increased with v according to a power function (C=155.2·ν 1.67;r=0.88). AlsoD could be described as a power function of the speed:D=12.3·ν 2.21;r= 0.94). The overall efficiency of motion, as obtained from the ratio ofD toC increased with speed from 9.2% at 1.41 m· s−1 to 14.5% at 3.08 m·s−1. It is concluded that, in spite of this relatively low efficiency of motion, the gondola is a very economic means. Indeed, at low speeds (∼ 1 m·s−1), the absolute amount of energy for propelling a gondola is the same as that for waking on the level at the same speed for a subject of 70 kg body mass.Type of Medium: Electronic ResourceURL: -
8Articles: DFG German National LicensesStaff View
ISSN: 1439-6327Keywords: Cycling ; Altitude ; Best performances ; Energy cost of cyclingSource: Springer Online Journal Archives 1860-2000Topics: MedicineNotes: Abstract The present world record for 1 h unaccompanied cycling (55.291 km) was set by T. Rominger in November 1994 at sea level (Bordeaux, France). However, maximal aerobic cycling performances can be expected to increase at altitude because, for a given air temperature, air density decreases more than VO2max. The combined effect of these opposite trends results in an improvement of performances. In this study, based on the aerodynamics of track cycling, and assuming an average decrease of VO2max with altitude as from the literature, we show that the ideal altitude for Rominger is 4000 m where he could cover 60.1 km in 1 h. To our knowledge, only two cyclists attempted at close time intervals to set the 1 h record at sea level and at altitude (Mexico, 2230 m above sea level): F. Moser and J. Longo. Their increase of performance with altitude was only about 50% of that predicted on the basis of similar calculations as performed on Rominger. This suggests that the decrease of VO2max resulting from altitude is greater for athletes than for average trained subjects and/or that the fraction of VO2max that can be maintained throughout 1 h decreases with altitude.Type of Medium: Electronic ResourceURL: -
9Articles: DFG German National LicensesStaff View
ISSN: 1439-6327Keywords: Key words Energy cost of swimming ; Maximal metabolic power ; Underwater torque ; Maximal performancesSource: Springer Online Journal Archives 1860-2000Topics: MedicineNotes: Abstract The energy cost of front-crawl swimming (Cs, kJ · m−1) at maximal voluntary speeds over distances of 50, 100, 200 and 400 m, and the underwater torque (T′) were assessed in nine young swimmers (three males and six females; 12–17 years old). Cs was calculated from the ratio of the total metabolic energy (E s, kJ) spent to the distance covered. E s was estimated as the sum of the energy derived from alactic (AnAl), lactic (AnL) and aerobic (Aer) processes. In turn, AnL was obtained from the net increase of lactate concentration after exercise, AnAl was assumed to amount to 0.393 kJ · kg−1 of body mass, and Aer was estimated from the maximal aerobic power of the subject. Maximal oxygen consumption was calculated by means of the back-extrapolation technique from the oxygen consumption kinetics recorded during recovery after a 400-m maximal trial. Underwater torque (T′, N · m), defined as the product of the force with which the feet of a subject lying horizontally in water tends to sink times the distance from the feet to the center of volume of the lungs, was determined by means of an underwater balance. Cs (kJ · m−1) turned out to be a continuous function of the speed (v, m · s−1) in both males (Cs=0.603 · 100.228 v , r 2=0.991; n=12) and females (Cs=0.360 · 100.339 v , r 2=0.919; n=24). A significant relationship was found between T′ and Cs at 1.2 m · s−1; Cs=0.042T′ + 0.594, r=0.839, n=10, P 〈 0.05. On the contrary, no significant relationships were found between Cs and T′ at faster speeds (1.4 and 1.6 m · s−1). This suggests that T′ is a determinant of Cs only at speeds comparable to that maintained by the subjects over the longest, 400-m distance [mean (SD) 1.20 (0.07) m · s−1].Type of Medium: Electronic ResourceURL: -
10Articles: DFG German National LicensesStaff View
ISSN: 1439-6327Keywords: Key words Energy cost of cycling ; Human-powered vehicles ; Mechanical efficiency ; Best performance timesSource: Springer Online Journal Archives 1860-2000Topics: MedicineNotes: Abstract Oxygen consumption at steady state (V˙O 2, l · min−1) and mechanical power (W˙, W) were measured in five subjects riding a human-powered vehicle (HPV, the Karbyk, a four-wheeled recumbent cycle) on a flat concrete road at constant sub-maximal speeds. The external mechanical work spent per unit of distance (W, J · m−1), as calculated from the ratio of W˙ to the speed (v, m · s−1), was found to increase with the square of v: W˙=8.12+(0.262 ·v 2) (r=0.986, n=31), where the first term represents the mechanical energy wasted, over a unit of distance, against frictional forces (rolling resistance, Rr), and the second term (k · v 2) is the work performed, per unit distance, to overcome the air drag. The rolling coefficient (Cr, obtained dividing Rr by m · g, where m is the overall mass and g is the acceleration of gravity) amounted to [mean (SD)] 0.0084 (0.0008), that is about 60% higher than that of a racing bicycle. The drag coefficient was calculated from the measured values of k, air density (ρ) and frontal area (A) [Cx=k · (0.5 · A · ρ)−1], and amounted to 1.067 (0.029), that is about 20% higher than that of a racing bicycle. The energy cost of riding the HPV (Ck, J · m−1) was measured from the ratio of metabolic power above rest (net V˙O 2, expressed in J · s−1) to the speed (v, m · s−1); the value of this parameter increased with the square of v, as described by: Ck=61.45 + (0.675 · v 2) (r=0.711, n=23). The net mechanical efficiency (η) was calculated from the ratio of W to Ck: over the investigated speed range this turned out to be 0.22 (0.021). Best performance times (BPTs) of a “typical”élite athlete riding the Karbyk were calculated over the distances of 1, 5 and 10 km: these were about 8% longer than the BPTs calculated, on the same subjects, when riding a conventional racing bicycle.Type of Medium: Electronic ResourceURL: -
11Articles: DFG German National LicensesStaff View
ISSN: 1439-6327Keywords: Key words Concentric exercise ; Counter movement jumps ; Elastic recoil ; Simulated low gravitySource: Springer Online Journal Archives 1860-2000Topics: MedicineNotes: Abstract Maximal explosive power during two-leg jumps was measured on four sedentary subjects [mean age 43.0 (SD 10.3) years, mean height 1.74 (SD 0.04) m, mean body mass 73.5 (SD 1.3) kg] using a sledge apparatus with which both force and speed could be directly measured. Different after-loads were obtained by positioning the sledge at five different angles (SA, α) in respect to the horizontal so that m · g · sin α (where m is the sum of body mass and the mass of the sledge seat, g the acceleration due to gravity) decreased (on average) from 78% body mass at 30° to 27% body mass at 10°, thus simulating conditions of low gravity. The subjects were asked to jump maximally, without counter movement, starting from 70°, 90°, 110°, and 140° of knee angle (KA); the protocol being repeated at 10°, 15°, 20°, 25° and 30° SA. The average (W˙ mean +) power output during concentric exercise (CE) was found to decrease when the starting KA was increased, but to be unaffected by SA (i.e. by the after-load, the simulated low g). The higher values of W˙ mean + were recorded at 90° KA [15.01 (SD 1.46) W · kg−1, average for all subjects at all SA]. The subjects were also asked to perform counter movement (CMJ) and rebound jumps (RE) at the same SA as for CE. In CMJ and RE maximal power outputs were also found to be unaffected by the SA; W˙ mean + amounted to 16.03 (SD 0.28) W · kg−1 in CMJ and 16.88 (SD 0.36) W · kg−1 in RE (average for all subjects at all SA). In CE, CMJ and RE, the instantaneous force at the onset of the positive speed phase (F i) was found to increase linearly with SA (i.e. with increasing m · g · sin α), and the difference between F i in CMJ or RE and F i in CE (F i in CMJ minus F i in CE and F i in RE minus F i in CE) was unaffected by SA. This indicated that both maximal power and the elastic recoil were unaffected by simulated low g ranging from 1.71 m · s−2 (at 10° SA) to 4.91 m · s−2 (at 30° SA).Type of Medium: Electronic ResourceURL: -
12Articles: DFG German National LicensesBrueckner, J. C. ; Atchou, G. ; Capelli, C. ; Duvallet, A. ; Barrault, D. ; Jousselin, E. ; Rieu, M. ; Prampero, P. E.
Springer
Published 1991Staff ViewISSN: 1439-6327Keywords: Energy cost of running ; Distance ; FatigueSource: Springer Online Journal Archives 1860-2000Topics: MedicineNotes: Summary The net energy cost of running per unit of body mass and distance (Cr, ml O2·kg−1·km−1) was determined on ten amateur runners before and immediately after running 15, 32 or 42 km on an indoor track at a constant speed. The Cr was determined on a treadmill at the same speed and each run was performed twice. The average value of Cr, as determined before the runs, amounted to 174.9 ml O2·kg−1·km−1 SD 13.7. After 15 km, Cr was not significantly different, whereas it had increased significantly after 32 or 42 km, the increase ranging from 0.20 to 0.31 ml O2·kg−1·km−1 per km of distance (D). However, Cr before the runs decreased, albeit at a progressively smaller rate, with the number of trials (N), indicating an habituation effect (H) to treadmill running. The effects of D alone were determined assuming that Cr increased linearly with D, whereas H decreased exponentially with increasing N, i.e.C r =C r0+aD+He−bN. The Cro, the “true” energy cost of running in nonfatigued subjects accustomed to treadmill running, was assumed to be equal to the average value of Cr before the run for N equal to or greater than 7 (171.1 ml O2·kg−1·km−1, SD 12.7;n = 30). A multiple regression of Cr on N and D in the form of the above equation showed firstly that Cr increased with the D covered by 0.123%·km−1, SEM 0.006 (i.e. about 0.22 ml O2·kg−1·km−1 per km,P〈0.001); secondly, that in terms of energy consumption (obtained from oxygen consumption and the respiratory quotient), the increase of Cr with D was smaller, amounting on average to 0.08%·km−1 (0.0029 J·kg−1·m−1,P〈0.001) and thirdly that the effects of H amounted to about 16% of Cr0 for the first trial and became negligible after three to four trials.Type of Medium: Electronic ResourceURL: -
13Articles: DFG German National LicensesStaff View
ISSN: 1439-6327Keywords: Stroke volume ; Pulse contour ; Pulsed Doppler echography ; FinapresSource: Springer Online Journal Archives 1860-2000Topics: MedicineNotes: Abstract The stroke volume of the left ventricle (SV) was calculated from noninvasive recordings of the arterial pressure using a finger photoplethysmograph and compared to the values obtained by pulsed Doppler echocardiography (PDE). A group of 19 healthy men and 12 women [mean ages: 20.8 (SD 1.6) and 22.2 (SD 1.6) years respectively] were studied at rest in the supine position. The ratio of the area below the ejection phase of the arterial pressure wave (A s) to SV, as obtained by PDE, yielded a “calibration factor” dimensionally equal to the hydraulic impedance of the system (Z ao =A s ·SV −1). TheZ ao amounted on average to 0.062 (SD 0.018) mmHg · s · cm−3 for the men and to 0.104 (SD 0.024) mmHg · s · cm−3 for the women. TheZ ao was also estimated from the equation:Z ao = a · (d + b ·HR + c ·PP + e ·MAP)−1, whereHR was the heart rate,PP the pulse pressure,MAP the mean arterial pressure and the coefficients of the equation were obtained by an iterating statistical package. The value ofZ ao thus obtained allowed the calculation of SV from measurements derived from the photoplethysmograph only. The mean percentage error between the SV thus obtained and those experimentally determined by PDE amounted to 14.8 and 15.6 for the men and the women, respectively. The error of the estimate was reduced to 12.3 and to 11.1, respectively, if the factorZ ao, experimentally obtained from a given heart beat, was subsequently applied to other beats to obtain SV from theA s measurement in the same subject.Type of Medium: Electronic ResourceURL: -
14Articles: DFG German National LicensesZamparo, P. ; Capelli, C. ; Termin, B. ; Pendergast, D. R. ; Prampero, P. E.
Springer
Published 1996Staff ViewISSN: 1439-6327Keywords: Energy cost of swimming ; Efficiency ; Active body drag ; Under water torqueSource: Springer Online Journal Archives 1860-2000Topics: MedicineNotes: Abstract Underwater torque (T′) is defined as the product of the force with which the swimmer's feet tend to sink times the distance between the feet and the centre of volume of the lungs. It has previously been shown that experimental changes ofT′, obtained by securing around the swimmer's waist a plastic tube filled, on different occasions, with air, water or 2-kg lead, were accompanied by changes in the energy cost of swimming per unit of distance (CS) at any given speed. The aim of this study was to investigate whether the observed increases of CS withT′ during front crawl swimming were due to an increase of active body drag (Db), a decrease of drag efficiency (ηd) or both. The effect of experimental changes ofT′ on CS, Db and ηd were therefore studied on a group of eight male elite swimmers at two submaximal speeds (1.00 and 1.23 m · s−1). To compare different subjects and different speeds, the individual data for CS, Db,ηd andT′ were normalized dividing them by the corresponding individual averages. These were calculated from all individual data (of CS, Db, ηd andT′) obtained from that subject at that speed. It was found that, between the two extremes of this study (tube filled with air and with 2-kg lead),T′ increased by 73% and that CS, Db and ηd increased linearly withT′. The increase of CS between the two extremes was intermediate ( ≈ 20%) between that of Db (≈ 35%) and of ηd ( ≈ 16%). Thus, the actual strategy implemented by the swimmers to counteractT′, was to tolerate a large increase of Db. This led also to a substantial (albeit smaller) increase of did, the effect of which was to reduce the increase of CS that would otherwise have occurred.Type of Medium: Electronic ResourceURL: -
15Articles: DFG German National LicensesZamparo, P. ; Antonutto, G. ; Capelli, C. ; Girardis, M. ; Sepulcri, L. ; di Prampero, P. E.
Springer
Published 1997Staff ViewISSN: 1439-6327Keywords: Key words Jumping test ; Maximal explosive power ; Elastic recoilSource: Springer Online Journal Archives 1860-2000Topics: MedicineNotes: Abstract The maximal explosive power during a two legs jump was measured on four competitive athletes [mean age 24 (SD 4.3) years; height 1.79 (SD 0.09) m; body mass 68.7 (SD 12.8) kg] at different starting knee angles (70, 90, 110, 130 and 150°). The experiments were performed on a newly developed instrument with which both force and speed could be measured using a force platform and a wire tachometer, respectively, and on a conventional force platform. At the smallest knee angle (70°) the mean power output ( $\bar\dot W$ in watts per kilogram) developed during the jump was found not to differ significantly between the two methods (P 〉 0.1). At the larger knee angles $\bar \dot W$ was 18.4% (90°), 34.5% (110°), 47.4% (130°) and 19.4% (150°) higher using the conventional force platform (P 〈 0.05 throughout). The difference of $\bar \dot W$ between the two methods was attributed to the recovery of elastic energy due to the counter movement which immediately preceded the jump on the conventional platform, but not on the newly developed instrument. Indeed because of a mechanical arrangement which prevented the subject from moving towards the platforms, eccentric work (W −) could not be performed on the newly developed instrument; whereas W − on the conventional force platform was almost negligible at 70° knee angle [mean 1.7 (SD 2.3 J)] reached a maximum of 13.1 (SD 7.9) J at 130° and decreased again to a mean 4.7 (SD 3.6) J for the largest angle (150°). Furthermore, on the conventional force platform, the force at the onset of the positive speed phase (F i) was an increasing function of W − (r 2 = 0.519, P 〈 0.001); and the difference of $\bar \dot W$ between the conventional and new instruments was larger the larger the difference of F i (r 2 = 0.391, P 〈 0.01).Type of Medium: Electronic ResourceURL: -
16Articles: DFG German National LicensesStaff View
ISSN: 1439-6327Keywords: Key words Bedrest ; Electromyography ; Maximal voluntary isometric contraction ; Maximal isometric torque ; Muscle atrophy ; Plantar and dorsal flexors of the ankleSource: Springer Online Journal Archives 1860-2000Topics: MedicineNotes: Abstract Maximal voluntary isometric torque values of the ankle plantar (T im,PF) and dorsal flexors (T im,DF) were assessed in eight healthy adult males at 5° and 15° of dorsal flexion (DF) and at 5°, 15° and 25° of plantar flexion (PF) with the knee at right angles, before (two times), during (three times) and after (three times) 17 days of 6° head-down tilt bedrest (BR). Integrated electromyograms (iEMG) were also recorded from the gastrocnemius medialis and tibialis anterior. T im,PF and the iEMG of the gastrocnemius medialis were significantly larger (by 14% and by 27%, respectively) at the end of recovery than before BR. This was probably the consequence of training and/or habituation leading to: (1) increased activation of the plantar flexors; and (2) decreased co-activation of the antagonist muscles. Neither T im,DF nor the tibialis anterior iEMG changed significantly. The effects of BR on muscle performance were evaluated as follows. The net torque generated by a given muscle group was assumed to be the algebraic sum of the torque generated by the agonists and by the antagonists. Thus, for the plantar flexors Tim,PF=αiEMGGm − βiEMGTa, where: (1) iEMGGm and iEMGTa are the iEMGs of gastrocnemius medialis and of tibialis anterior during maximal PF; and (2) the constants α and β represent the electromechanical coupling of the plantar (α) and dorsal (β) flexors. Similarly for the dorsal flexors: Tim,DF=βiEMGTa − αiEMGGm, where iEMGTa and iEMGGm are the iEMGs of tibialis anterior and gastrocnemius medialis during maximal DF. Torque and iEMG values were assessed for all subjects under all experimental conditions. Thus, since the biomechanical leverage of the system was constant, α and β could be calculated. During BR, α decreased by 25% and it dropped by a further 30% during recovery. In contrast, β remained almost unchanged. This suggests that, in spite of training and/or habituation, BR significantly impaired the maximal isometric performance of the plantar flexors, an effect that continued during the initial 10 days of recovery.Type of Medium: Electronic ResourceURL: -
17Articles: DFG German National LicensesStaff View
ISSN: 1439-6327Keywords: Key words Energy cost of locomotion ; Kayaking ; Metabolic power ; LactateSource: Springer Online Journal Archives 1860-2000Topics: MedicineNotes: Abstract The energy cost of kayaking per unit distance (Ck, kJ · m−1) was assessed in eight middle- to high-class athletes (three males and five females; 45–76 kg body mass; 1.50–1.88 m height; 15–32 years of age) at submaximal and maximal speeds. At submaximal speeds, Ck was measured by dividing the steady-state oxygen consumption (V˙O2, l · s−1) by the speed (v, m · s−1), assuming an energy equivalent of 20.9 kJ · l O−1 2. At maximal speeds, Ck was calculated from the ratio of the total metabolic energy expenditure (E, kJ) to the distance (d, m). E was assumed to be the sum of three terms, as originally proposed by Wilkie (1980): E = AnS + αV˙O2max · t−αV˙O2max · τ(1−e −t·τ−1), were α is the energy equivalent of O2 (20.9 kJ · l O2 −1), τ is the time constant with which V˙O2max is attained at the onset of exercise at the muscular level, AnS is the amount of energy derived from anaerobic energy utilization, t is the performance time, and V˙O2max is the net maximal V˙O2. Individual V˙O2max was obtained from the V˙O2 measured during the last minute of the 1000-m or 2000-m maximal run. The average metabolic power output (E˙, kW) amounted to 141% and 102% of the individual maximal aerobic power (V˙O2max) from the shortest (250 m) to the longest (2000 m) distance, respectively. The average (SD) power provided by oxidative processes increased with the distance covered [from 0.64 (0.14) kW at 250 m to 1.02 (0.31) kW at 2000 m], whereas that provided by anaerobic sources showed the opposite trend. The net Ck was a continuous power function of the speed over the entire range of velocities from 2.88 to 4.45 m · s−1: C k = 0.02 · v 2.26 (r = 0.937, n = 32).Type of Medium: Electronic ResourceURL: