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Open accessJournal ArticleDOI: 10.1080/17461391.2020.1753816

Comparison of linear, hyperbolic and double-hyperbolic models to assess the force-velocity relationship in multi-joint exercises.

04 Mar 2021-European Journal of Sport Science (Informa UK Limited)-Vol. 21, Iss: 3, pp 359-369
Abstract: This study assessed the validity of linear, hyperbolic and double-hyperbolic models to fit measured force–velocity (F–V) data in multi-joint exercises and the influence of muscle excitation on the ...

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Open accessJournal ArticleDOI: 10.1371/JOURNAL.PONE.0245791
01 Feb 2021-PLOS ONE
Abstract: The aim of the study was to examine the test-retest reliability and agreement across methods for assessing individual force-velocity (FV) profiles of the lower limbs in athletes Using a multicenter approach, 27 male athletes completed all measurements for the main analysis, with up to 82 male and female athletes on some measurements The athletes were tested twice before and twice after a 2- to 6-month period of regular training and sport participation The double testing sessions were separated by ~1 week Individual FV-profiles were acquired from incremental loading protocols in squat jump (SJ), countermovement jump (CMJ) and leg press A force plate, linear encoder and a flight time calculation method were used for measuring force and velocity during SJ and CMJ A linear regression was fitted to the average force and velocity values for each individual test to extrapolate the FV-variables: theoretical maximal force (F0), velocity (V0), power (Pmax), and the slope of the FV-profile (SFV) Despite strong linearity (R2>095) for individual FV-profiles, the SFV was unreliable for all measurement methods assessed during vertical jumping (coefficient of variation (CV): 14-30%, interclass correlation coefficient (ICC): 036-079) Only the leg press exercise, of the four FV-variables, showed acceptable reliability (CV:37-83%, ICC:082-098) The agreement across methods for F0 and Pmax ranged from (Pearson r): 056-095, standard error of estimate (SEE%): 58-188, and for V0 and SFV r: -039-078, SEE%: 122-372 With a typical error of 15 cm (5-10% CV) in jump height, SFV and V0 cannot be accurately obtained, regardless of the measurement method, using a loading range corresponding to 40-70% of F0 Efforts should be made to either reduce the variation in jumping performance or to assess loads closer to the FV-intercepts Coaches and researchers should be aware of the poor reliability of the FV-variables obtained from vertical jumping, and of the differences across measurement methods

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Topics: Jumping (52%)

5 Citations


Journal ArticleDOI: 10.1123/IJSPP.2020-0308
Abstract: PURPOSE To analyze the differences in the force-velocity (F-v) profile assessed under unconstrained (ie, using free weights) and constrained (ie, on a Smith machine) vertical jumps, as well as to determine the between-day reliability. METHODS A total of 23 trained participants (18 [1] y) performed an incremental load squat jump test (with ∼35%, 45%, 60%, and 70% of the subjects' body mass) on 2 different days using free weights and a Smith machine. Nine of these participants repeated the tests on 2 other days for an exploratory analysis of between-day reliability. F-v variables (ie, maximum theoretical force [F0], velocity [v0], and power, and the imbalance between the actual and the theoretically optimal F-v profile) were computed from jump height. RESULTS A poor agreement was observed between the F-v variables assessed under constrained and unconstrained conditions (intraclass correlation coefficient [ICC] .70). The F-v variables computed under constrained conditions showed an overall good agreement (ICC = .75-.95 for all variables) and no significant differences between days (P > .05), but a high variability for v0, the imbalance between the actual and the theoretically optimal F-v profile, and maximal theoretical power (coefficient of variation = 17.0%-27.4%). No between-day differences were observed for any F-v variable assessed under unconstrained conditions (P > .05), but all of the variables presented a low between-day reliability (coefficient of variation > 10% and ICC < .70 for all). CONCLUSIONS F-v variables differed meaningfully when obtained from constrained and unconstrained loaded jumps, and most importantly seemed to present a low between-day reliability.

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4 Citations


Journal ArticleDOI: 10.1123/IJSPP.2020-0692
Abstract: PURPOSE This study aimed to compare the adaptations provoked by various velocity loss (VL) thresholds used in resistance training on the squat force-velocity (F-V) relationship. METHODS Sixty-four resistance-trained young men were randomly assigned to one of four 8-week resistance training programs (all 70%-85% 1-repetition maximum) using different VL thresholds (VL0 = 0%, VL10 = 10%, VL20 = 20%, and VL40 = 40%) in the squat exercise. The F-V relationship was assessed under unloaded and loaded conditions in squat. Linear and hyperbolic (Hill) F-V equations were used to calculate force at zero velocity (F0), velocity at zero force (V0), maximum muscle power (Pmax), and force produced at mean velocities ranging from 0.0 to 2.0 m·s-1. Changes in parameters derived from the F-V relationship were compared among groups using linear mixed models. RESULTS Linear equations showed increases in F0 (120.7 N [89.4 to 152.1]) and Pmax (76.2 W [45.3 to 107.2]) and no changes in V0 (-0.02 m·s-1 [-0.11 to 0.06]) regardless of VL. Hyperbolic equations depicted increases in F0 (120.7 N [89.4 to 152.1]), V0 (1.13 m·s-1 [0.78 to 1.48]), and Pmax (198.5 W [160.5 to 236.6]) with changes in V0 being greater in VL0 and VL10 versus VL40 (both P < .001). All groups similarly improved force at 0.0 to 2.0 m·s-1 (all P < .001), although in general, effect sizes were greater in VL10 and VL20 versus VL0 and VL40 at velocities ≤0.5 m·s-1. CONCLUSIONS All groups improved linear and hyperbolic F0 and Pmax and hyperbolic V0 (except VL40). The dose-response relationship exhibited an inverted U-shape pattern at velocities ≤0.5 m·s-1 with VL10 and VL20 showing the greatest standardized changes.

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1 Citations


Journal ArticleDOI: 10.1016/J.EXGER.2021.111595
Abstract: Background Lower limb muscle strength is an important determinant of physical function in older adults. However, its measure in clinical settings is limited because of the requirement for large-scale and costly equipment. A new simple protocol based on sit-to-stand test (STS) is developed to measure force velocity (F-v) and power velocity (P-v) profile in the community-dwelling older adults. Objective The objective of this study was to assess the validity of this new methodology for measuring F-v and P-v profile compared to the gold standard isokinetic BIODEX. Participants 46 older people aged 65–85 years (M = 73.7; SD = 7.7). Methods F-v and P-v profiles were assessed in participants on their dominant leg. The concurrent validity of STS was tested using Spearman's rank correlation coefficient and Passing Bablok: maximal power output Pmax, optimal velocity and force Vopt and Fopt, maximal force at null velocity F0, maximal unloaded velocity V0 and coefficient of F-v (SFV) and P-v equation (a_poly, b_poly). Results No proportional difference for F0 and b_poly and a low significant correlation for Pmax (r = 0.314), Sfv (r = 0.229), a_poly (r = 0.335) and b_poly (r = 0.226) whereas the other parameters were non correlated significantly. Conclusion STS method is moderately reliable on force and power parameters whereas further improvements are needing for velocity parameters. However, its feasibility, portability and lower cost compared to other methods makes it very affordable in clinical context and will allow easy investigation of aging population.

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Open accessJournal ArticleDOI: 10.1111/SMS.14035
Abstract: This study aimed to determine deficits in knee extensor muscle function through the torque-time and torque-velocity relationships and whether these deficits are associated with reduced functional performance in postmenopausal women with knee osteoarthritis (KOA). A clinical sample of postmenopausal women with established KOA (n = 18, ≥55 years) was compared to an age-matched healthy control sample (CON) (n = 26). The deficits in different parameters of the knee extensor torque-time (maximal isometric torque and rate of torque development) and torque-velocity relationship (maximum muscle power, maximal velocity and torque at 0-500°·s-1 ) were assessed through a protocol consisting of isometric, isotonic and isokinetic tests. Functional performance was evaluated with sit-to-stand and stair-climbing tasks using a sensor-based technology (ie, time- and power-based outcomes). Postmenopausal women with KOA showed reduced maximal isometric torque (Hedge's g effect size (g) = 1.05, p = 0.001) and rate of torque development (g = 0.77-1.17, all p ≤ 0.02), combined with impaired torque production at slow to moderate velocities (g = 0.92-1.70, p ≤ 0.004), but not at high or maximal velocities (g = 0.16, p > 0.05). KOA were slower (g = 0.81-0.92, p ≤ 0.011) and less powerful (g = 1.11-1.29, p ≤ 0.001) during functional tasks. Additionally, knee extensor deficits were moderately associated with power deficits in stair climbing (r = 0.492-0.659). To conclude, knee extensor muscle weakness was presented in postmenopausal women with KOA, not only as limited maximal and rapid torque development during isometric contractions, but also dynamically at low to moderate velocities. These deficits were related to impaired functional performance. The assessment of knee extensor muscle weakness through the torque-time and torque-velocity relationships might enable individual targets for tailored exercise interventions in KOA.

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Topics: Isometric exercise (53%)

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41 results found


Open accessJournal ArticleDOI: 10.1098/RSPB.1938.0050
Archibald Vivian Hill1Institutions (1)
Abstract: The hope was recently expressed (Hill 1937, p. 116) that with the development of a more accurate and rapid technique for muscle heat measurement, a much more consistent picture might emerge of the energy relations of muscles shortening (or lengthening) and doing positive (or negative) work. This hope has been realized, and some astonishingly simple and accurate relations have been found, relations, moreover, which (among other things) determine the effect of load on speed of shortening, allow the form of the isometric contraction to be predicted, and are the basis of the so-called “visco-elasticity” of skeletal muscle. This paper is divided into three parts. In Part I further developments of the technique are described: everything has depended on the technique, so no apology is needed for a rather full description of it and of the precautions necessary. In Part II the results themselves are described and discussed. In Part III the “visco-elastic” properties of active muscle are shown to be a consequence of the properties described in Part II.

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Topics: Work loop (55%), Hill's muscle model (53%), Isometric exercise (52%)

4,538 Citations


Journal ArticleDOI: 10.1016/S1050-6411(00)00027-4
Abstract: The knowledge of surface electromyography (SEMG) and the number of applications have increased considerably during the past ten years. However, most methodological developments have taken place locally, resulting in different methodologies among the different groups of users. A specific objective of the European concerted action SENIAM (surface EMG for a non-invasive assessment of muscles) was, besides creating more collaboration among the various European groups, to develop recommendations on sensors, sensor placement, signal processing and modeling. This paper will present the process and the results of the development of the recommendations for the SEMG sensors and sensor placement procedures. Execution of the SENIAM sensor tasks, in the period 1996–1999, has been handled in a number of partly parallel and partly sequential activities. A literature scan was carried out on the use of sensors and sensor placement procedures in European laboratories. In total, 144 peer-reviewed papers were scanned on the applied SEMG sensor properties and sensor placement procedures. This showed a large variability of methodology as well as a rather insufficient description. A special workshop provided an overview on the scientific and clinical knowledge of the effects of sensor properties and sensor placement procedures on the SEMG characteristics. Based on the inventory, the results of the topical workshop and generally accepted state-of-the-art knowledge, a first proposal for sensors and sensor placement procedures was defined. Besides containing a general procedure and recommendations for sensor placement, this was worked out in detail for 27 different muscles. This proposal was evaluated in several European laboratories with respect to technical and practical aspects and also sent to all members of the SENIAM club (>100 members) together with a questionnaire to obtain their comments. Based on this evaluation the final recommendations of SENIAM were made and published (SENIAM 8: European recommendations for surface electromyography, 1999), both as a booklet and as a CD-ROM. In this way a common body of knowledge has been created on SEMG sensors and sensor placement properties as well as practical guidelines for the proper use of SEMG.

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4,235 Citations


Journal ArticleDOI: 10.1152/PHYSREV.00031.2010
Stefano Schiaffino1, Carlo Reggiani1Institutions (1)
Abstract: Mammalian skeletal muscle comprises different fiber types, whose identity is first established during embryonic development by intrinsic myogenic control mechanisms and is later modulated by neural and hormonal factors. The relative proportion of the different fiber types varies strikingly between species, and in humans shows significant variability between individuals. Myosin heavy chain isoforms, whose complete inventory and expression pattern are now available, provide a useful marker for fiber types, both for the four major forms present in trunk and limb muscles and the minor forms present in head and neck muscles. However, muscle fiber diversity involves all functional muscle cell compartments, including membrane excitation, excitation-contraction coupling, contractile machinery, cytoskeleton scaffold, and energy supply systems. Variations within each compartment are limited by the need of matching fiber type properties between different compartments. Nerve activity is a major control mechanism of the fiber type profile, and multiple signaling pathways are implicated in activity-dependent changes of muscle fibers. The characterization of these pathways is raising increasing interest in clinical medicine, given the potentially beneficial effects of muscle fiber type switching in the prevention and treatment of metabolic diseases.

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Topics: Myocyte (58%), Skeletal muscle (58%), Myosin (56%) ... show more

1,668 Citations


Richard L. Lieber1, Jan Fridén2Institutions (2)
01 Nov 2000-Muscle & Nerve
Abstract: Skeletal muscle architecture is the structural property of whole muscles that dominates their function. This review describes the basic architectural properties of human upper and lower extremity muscles. The designs of various muscle groups in humans and other species are analyzed from the point of view of optimizing function. Muscle fiber arrangement and motor unit arrangement is discussed in terms of the control of movement. Finally, the ability of muscles to change their architecture in response to immobilization, eccentric exercise, and surgical tendon transfer is reviewed. Future integrative physiological studies will provide insights into the mechanisms by which such adaptations occur. It is likely that muscle fibers transduce both stress and strain and respond by modifying sarcomere number in a way more suited to the new biomechanical environment.

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Topics: Muscle architecture (60%), Physiological cross-sectional area (60%), Skeletal muscle (57%) ... show more

901 Citations


Journal ArticleDOI: 10.1249/00005768-199311000-00013
Abstract: This study was performed to determine which of three theoretically optimal resistance training modalities resulted in the greatest enhancement in the performance of a series of dynamic athletic activities. The three training modalities included 1) traditional weight training, 2) plyometric training, and 3) explosive weight training at the load that maximized mechanical power output. Sixty-four previously trained subjects were randomly allocated to four groups that included the above three training modalities and a control group. The experimental groups trained for 10 wk performing either heavy squat lifts, depth jumps, or weighted squat jumps. All subjects were tested prior to training, after 5 wk of training and at the completion of the training period. The test items included 1) 30-m sprint, 2) vertical jumps performed with and without a countermovement, 3) maximal cycle test, 4) isokinetic leg extension test, and 5) a maximal isometric test. The experimental group which trained with the load that maximized mechanical power achieved the best overall results in enhancing dynamic athletic performance recording statistically significant (P < 0.05) improvements on most test items and producing statistically superior results to the two other training modalities on the jumping and isokinetic tests.

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Topics: Strength training (53%), Squat (51%)

746 Citations


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