The current study aimed to investigate the effect of ankle restriction on the coordination of vertical jumping and discuss the influence of energy transfer through m. gastrocnemius on the multijoint movement. Eight participants performed two types of vertical jumps: a normal squat jump, and a squat jump with restricted ankle joint movement. Mechanical outputs were calculated using an inverse dynamics analysis. Custom-made shoes were used to restrict plantar flexion, resulting in significantly (P < .001) reduced maximum power and work at the ankle joint to below 2% and 3%, while maintaining natural range of motion at the hip and knee. Based on the comparison between the two types of jumps, we determined that the ankle restriction increased (P < .001) the power (827 ± 346 W vs. 1276 ± 326 W) and work (92 ± 34 J vs. 144 ± 36 J) at the knee joint. A large part of the enhanced output at the knee is assumed to be due to ankle restriction, which results in the nullification of energy transport via m. gastrocnemius; that is, reduced contribution of the energy transfer with ankle restriction appeared as augmentation at the knee joint.
Hiroshi Arakawa, Akinori Nagano, Dean C. Hay and Hiroaki Kanehisa
Randy J. Schmitz, John C. Cone, Timothy J. Copple, Robert A. Henson and Sandra J. Shultz
Potential biomechanical compensations allowing for maintenance of maximal explosive performance during prolonged intermittent exercise, with respect to the corresponding rise in injury rates during the later stages of exercise or competition, are relatively unknown.
To identify lower-extremity countermovement-jump (CMJ) biomechanical factors using a principal-components approach and then examine how these factors changed during a 90-min intermittent-exercise protocol (IEP) while maintaining maximal jump height.
Fifty-nine intermittent-sport athletes (30 male, 29 female) participated in experimental and control conditions.
Before and after a dynamic warm-up and every 15 min during the 1st and 2nd halves of an individually prescribed 90-min IEP, participants were assessed on rating of perceived exertion, sprint/cut speed, and 3-dimensional CMJ biomechanics (experimental). On a separate day, the same measures were obtained every 15 min during 90 min of quiet rest (control).
Main Outcome Measures:
Univariate piecewise growth models analyzed progressive changes in CMJ performance and biomechanical factors extracted from a principal-components analysis of the individual biomechanical dependent variables.
While CMJ height was maintained during the 1st and 2nd halves, the body descended less and knee kinetic and energetic magnitudes decreased as the IEP progressed.
The results indicate that vertical-jump performance is maintained along with progressive biomechanical changes commonly associated with decreased performance. A better understanding of lower-extremity biomechanics during explosive actions in response to IEP allows us to further develop and individualize performance training programs.
Niell G. Elvin, Alex A. Elvin and Steven P. Arnoczky
Modern electronics allow for the unobtrusive measurement of accelerations outside the laboratory using wireless sensor nodes. The ability to accurately measure joint accelerations under unrestricted conditions, and to correlate them with jump height and landing force, could provide important data to better understand joint mechanics subject to real-life conditions. This study investigates the correlation between peak vertical ground reaction forces, as measured by a force plate, and tibial axial accelerations during free vertical jumping. The jump heights calculated from force-plate data and accelerometer measurements are also compared. For six male subjects participating in this study, the average coefficient of determination between peak ground reaction force and peak tibial axial acceleration is found to be 0.81. The coefficient of determination between jump height calculated using force plate and accelerometer data is 0.88. Data show that the landing forces could be as high as 8 body weights of the jumper. The measured peak tibial accelerations ranged up to 42 g. Jump heights calculated from force plate and accelerometer sensors data differed by less than 2.5 cm. It is found that both impact accelerations and landing forces are only weakly correlated with jump height (the average coefficient of determination is 0.12). This study shows that unobtrusive accelerometers can be used to determine the ground reaction forces experienced in a jump landing. Whereas the device also permitted an accurate determination of jump height, there was no correlation between peak ground reaction force and jump height.
Pablo Floria, Luis A. Gómez-Landero and Andrew J. Harrison
The purpose of this study was to determine if children exhibit greater variability in center of mass movement and kinetics compared with adults in vertical jumping. Countermovement jumps with arms (CMJA) and without arms (CMJ) performed by 20 female children and 20 female adults were examined using force platform. The data were analyzed using continuous methods to determine differences in variability between groups and between types of jump. Jumping variability was measured by using the average coefficient of variation of the force-, velocity-, displacement-, and rate of force development-time curves across the jump. The analysis indicated that children and adults had similar levels of variability in the CMJ but different levels in the CMJA. In the CMJA, the children had a greater coefficient of variation than adults in force- (20 ± 7% and 12 ± 6%), velocity- (41 ± 14% and 22 ± 9%), displacement- (8 ± 16% and 23 ± 11%) and rate of force development-time (103 ± 46% and 75 ± 42%) curves, as well as in force-velocity relationship (6 ± 2% and 4 ± 2%). The results of analysis suggest that the variability depends on both the level of maturation of the participants as well as the task complexity.
Jason Brandenburg, William A. Pitney, Paul E. Luebbers, Arun Veera and Alicja Czajka
To examine the acute effects of static stretching on countermovement vertical-jump (CMVJ) ability and monitor the time course of any stretch-induced changes.
Once familiarized, 16 experienced jumpers completed 2 testing sessions in a randomized order. Each session consisted of a general warm-up, a pretreatment CMVJ assessment, a treatment, and multiple posttreatment CMVJ assessments. One treatment included lower-body static stretching, and the second treatment, involving no stretching, was the control. Posttreatment CMVJ measures occurred immediately, 3, 6, 12, and 24 minutes posttreatment. Stretching consisted of 3 static-stretching exercises, with each exercise repeated 3 times and each repetition held for 30 s.
Prestretch CMVJ height equaled 47.1 (± 9.7) cm. CMVJ height immediately poststretch was 45.7 (± 9.2) cm, and it remained depressed during the 24-min follow-up period. Pre-no-stretch CMVJ height was 48.4 (± 9.8) cm, whereas immediately post-no-stretch CMVJ height equaled 46.8 (± 9.5) cm, and as in the stretch treatment, post-no-stretch CMVJ height remained lower than pre-no-stretch values. Although there was a significant main effect of time (P = .005), indicating that CMVJ was lower and remained impaired after both treatments, no significant interaction effect (P = .749) was observed.
In comparison with the no-activity control, static stretching resulted in similar reductions in CMVJ ability when examined over the same time course, so athletes preparing for CMVJ should avoid periods of inactivity, as well as static stretching.
Lee N. Burkett, Joana Ziuraitis and Wayne T. Phillips
The effectiveness of two specific and two non-specific warm-ups on the vertical jump test for female athletes was the focus of this research. The four warm-up procedures were: (a) weighted jumping (WT), (b) submaximal vertical jumping (SUB), (c) stretching (ST), and (d) no warm-up (NW). To control for learning and fatigue, a counter-balanced design was used to test all participants over four different days. Thus all groups were tested in a predetermined order. Participants were 15 university female athletes (age 18 to 23 years). After warming up using one of the four warm-up procedures, three vertical jumps were measured and the best score was used for analysis. A single factors repeated measure analysis of variance and LSD post hoc tests revealed that the weighted jump warm-up procedure was statistically superior (p<0.01) to all other warm-up procedures. No warm-up was statistically inferior to all other warm-ups and submaximal vertical jumping was not statistically different than stretching. It was concluded; (a) performing a warmup is better than no warm-up, and (b) utilizing a weighted resistance-jumping warm-up will produce the highest scores when performing the vertical jump test for female athletes.
John R. Harry, Max R. Paquette, Brian K. Schilling, Leland A. Barker, C. Roger James and Janet S. Dufek
The countermovement vertical jump (CMVJ) is a useful physical performance test to evaluate athletic potential 1 – 3 due to its strong positive correlation to speed, power, agility, and strength performance. 2 – 6 Because of this strong relationship, researchers and practitioners aim to understand
K. Katsikari, Eleni Bassa, Dimitrios Skoufas, Savvas Lazaridis, Christos Kotzamanidis and Dimitrios A. Patikas
. This countermovement was followed by a vertical jump. During the DJ, the participants stood on a box and projected slowly 1 foot forward, whereas the contralateral foot left the box without pushing upward or forward. After landing, they jumped immediately as high as possible. Training Program A 10-week
Walter L. Jenkins, Dorsey Shelton Williams, Alex Durland, Brandon Adams and Kevin O’Brien
The use of foot orthoses has been evaluated during a variety of functional activities. Twelve college-aged active females wore two types of foot orthoses and performed a vertical jump to determine the biomechanical effect of the orthoses on lower extremity transverse plane movement during landing. Data collection included three-dimensional analysis of the tibia, knee, and hip. A repeated-measures ANOVA was performed to determine the differences between no orthoses, over-the-counter, and custom-made orthoses with transverse plane motion. At the hip joint, there was significantly less internal rotation (p < .05) in the over-the-counter condition as compared with the no orthoses condition. There was significantly less tibial internal rotation (p < .05) in the custom-made condition as compared with no orthoses. Over-the-counter devices decreased transverse plane motion at the hip, whereas custom-made devices decreased transverse plane motion of the tibia.
Walter L. Jenkins, D.S. Williams, Brandon Bevil, Sara Stanley, Michael Blemker, Drue Taylor and Kevin O’Brien
Excessive hip motion has been linked to lower extremity pathology. Foot orthoses are commonly used to control motion within lower extremity joints when lower extremity pathology and dysfunction are present. Few studies have investigated the effect of foot orthoses on hip angular kinematics during functional activities. Eighteen females and 18 males performed a vertical jump with and without a prefabricated foot orthoses to determine the biomechanical effect of foot orthoses on hip kinematics when landing from a jump. Data collection included three-dimensional motion analysis of the lower extremity. Paired t tests were performed to determine if differences existed within genders with and without foot orthoses. At the hip joint, there was significantly less hip adduction motion in the foot orthoses condition as compared with the no foot orthoses condition in females (p < .05). There were no differences between foot orthoses conditions in males. Females appear to have a different proximal response to foot orthoses when landing from a forward jump than males.