학술논문
Mechanical and Morphological Adaptations at the Lower Limb of Competitive American Football Players Through a Cluster Analysis
Document Type
Academic Journal
Author
Source
Brazilian Journal of Motor Behavior. July, 2023, Vol. 17 Issue 2, p315, 1 p.
Subject
Language
English
Abstract
Bibliographic references: Harman, EA, Rosenstein, MT, Frykman, PN, Rosenstein, RM, Kraemer, WJ. Estimation of Human Power Output from Vertical Jump. JStrength CondRes. 1991;5(3):116-20. Heinrich Leon Souza Viera Universidade Federal de [...]
Background: American football is a team sport in which the players are disposed in different attack and defense positions, where the main physical capabilities are strength, speed and power output. However, it is not clear how these different demands can lead to different musculoskeletal functional adaptations, and what their consequences are in the ability to produce forces. Aim: Investigate muscle mechanical, morphological properties of knee extensors muscles and power output of lower limb on competitive American football players. Material and methods: Twentytwo American football amateur players composed the sample. Vastus lateralis (VL) of the dominant limb muscle architecture was assessed using a b-mode ultrasound (Siemens Healthcare, Germany), where three images were taken for further analysis. One image was taken to analyze VL elastography. Torque-Velocity relationship and work knee extensors was assessed in an isokinetic dynamometer (Biodex Medical System 4, Shirley, USA) at three different angular velocities, such as 60[degrees]/s, 180[degrees]/s and 300[degrees]/s. The three velocities were normalized by the maximum voluntary isometric contraction. Lower limb power output was assessed using vertical squat jump (SJ) and countermovement jump (CMJ) in a force platform (AMTI OR6-6-2000), based on previous equations (1). SJ and CMJ peak and mean power were normalized by subject's body weight. A cluster analysis was employed to determine performance profiles within the American football players. Independent student t-test was used to compare the clusters, with significance level of a=0.05. Results: The results of the current research were that Cluster-1 group presented significant values, compared to Cluster-2, for SJ height, normalized peak power output of SJ (27%), and CMJ (25%); P<0.05. Cluster-2 presented higher values in the absolute knee torque at three velocities (16-21%) and work (23-26%); P<0.05, but after normalized, no significant values were found (P>0.05). These outcomes suggest that, physical capabilities of American Football players are related to the biological demand's dependent on the technical-tactical function performed during the game. Conclusions: In summary, American Football players with greater body mass (Cluster-2) have greater torque and work of the knee extensor muscles and power output in vertical jumps SJ and CMJ. In addition, Cluster-2 also presented greater VL muscle thickness, when compared to players with lower body mass (Cluster-1), without alterations between the clusters in the other variables of muscle architecture and elastography of VL. However, Cluster-1 players had higher relative output power and vertical jump height SJ and CMJ.
Background: American football is a team sport in which the players are disposed in different attack and defense positions, where the main physical capabilities are strength, speed and power output. However, it is not clear how these different demands can lead to different musculoskeletal functional adaptations, and what their consequences are in the ability to produce forces. Aim: Investigate muscle mechanical, morphological properties of knee extensors muscles and power output of lower limb on competitive American football players. Material and methods: Twentytwo American football amateur players composed the sample. Vastus lateralis (VL) of the dominant limb muscle architecture was assessed using a b-mode ultrasound (Siemens Healthcare, Germany), where three images were taken for further analysis. One image was taken to analyze VL elastography. Torque-Velocity relationship and work knee extensors was assessed in an isokinetic dynamometer (Biodex Medical System 4, Shirley, USA) at three different angular velocities, such as 60[degrees]/s, 180[degrees]/s and 300[degrees]/s. The three velocities were normalized by the maximum voluntary isometric contraction. Lower limb power output was assessed using vertical squat jump (SJ) and countermovement jump (CMJ) in a force platform (AMTI OR6-6-2000), based on previous equations (1). SJ and CMJ peak and mean power were normalized by subject's body weight. A cluster analysis was employed to determine performance profiles within the American football players. Independent student t-test was used to compare the clusters, with significance level of a=0.05. Results: The results of the current research were that Cluster-1 group presented significant values, compared to Cluster-2, for SJ height, normalized peak power output of SJ (27%), and CMJ (25%); P<0.05. Cluster-2 presented higher values in the absolute knee torque at three velocities (16-21%) and work (23-26%); P<0.05, but after normalized, no significant values were found (P>0.05). These outcomes suggest that, physical capabilities of American Football players are related to the biological demand's dependent on the technical-tactical function performed during the game. Conclusions: In summary, American Football players with greater body mass (Cluster-2) have greater torque and work of the knee extensor muscles and power output in vertical jumps SJ and CMJ. In addition, Cluster-2 also presented greater VL muscle thickness, when compared to players with lower body mass (Cluster-1), without alterations between the clusters in the other variables of muscle architecture and elastography of VL. However, Cluster-1 players had higher relative output power and vertical jump height SJ and CMJ.