Alterations in kinetic patterns of pedal force and crank torque due to changes in surface grade (level vs. 8% uphill) and posture (seated vs. standing) were investigated during cycling on a computerized ergometer. Kinematic data from a planar cine analysis and force data from a pedal instrumented with piezoelectric crystals were recorded from multiple trials of 8 elite cyclists. These measures were used to calculate pedal force, pedal orientation, and crank torque profiles as a function of crank angle in three conditions: seated level, seated uphill, and standing uphill. The change in surface grade from level to 8% uphill resulted in a shift in pedal angle (toe up) and a moderately higher peak crank torque, due at least in part to a reduction in the cycling cadence. However, the overall patterns of pedal and crank kinetics were similar in the two seated conditions. In contrast, the alteration in posture from sitting to standing on the hill permitted the subjects to produce different patterns of pedal and crank kinetics, characterized by significantly higher peak pedal force and crank torque that occurred much later in the downstroke. These kinetic changes were associated with modified pedal orientation (toe down) throughout the crank cycle. Further, the kinetic changes were linked to altered nonmuscular (gravitational and inertial) contributions to the applied pedal force, caused by the removal of the saddle as a base of support.
Search Results
Pedal and Crank Kinetics in Uphill Cycling
Graham E. Caldwell, Li Li, Steve D. McCole, and James M. Hagberg
The Effects of Postseason Break on Knee Biomechanics and Lower Extremity EMG in a Stop-Jump Task: Implications for ACL Injury
Boyi Dai, Christopher J. Sorensen, Timothy R. Derrick, and Jason C. Gillette
The effects of training on biomechanical risk factors for anterior cruciate ligament (ACL) injuries have been investigated, but the effects of detraining have received little attention. The purpose of this study was to evaluate the effects of a one-month postseason break on knee biomechanics and lower extremity electromyography (EMG) during a stop-jump task. A postseason break is the phase between two seasons when no regular training routines are performed. Twelve NCAA female volleyball players participated in two stop-jump tests before and after the postseason break. Knee kinematics, kinetics, quadriceps EMG, and hamstring EMG were assessed. After one month of postseason break, the players demonstrated significantly decreased jump height, decreased initial knee flexion angle, decreased knee flexion angle at peak anterior tibial resultant force, decreased prelanding vastus lateralis EMG, and decreased prelanding biceps femoris EMG as compared with prebreak. No significant differences were observed for frontal plane biomechanics and quadriceps and hamstring landing EMG between prebreak and postbreak. Although it is still unknown whether internal ACL loading changes after a postseason break, the more extended knee movement pattern may present an increased risk factor for ACL injuries.
Variability in the Application of Force During the Vertical Jump in Children and Adults
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.
No Combined Effect of Caffeinated Chewing Gum and Priming Exercise on Oxygen Uptake and Muscle Near-Infrared Spectroscopy-Derived Kinetics: A Double-Blind Randomized Crossover Placebo-Controlled Trial in Cyclists
Eduardo Marcel Fernandes Nascimento, Fernando Klitzke Borszcz, Thiago Pereira Ventura, Brunna Cristina Bremer Boaventura, Paulo Cesar do Nascimento Salvador, Luiz Guilherme Antonacci Guglielmo, and Ricardo Dantas de Lucas
Priming exercise has been widely used to explore the mechanistic bases of oxygen uptake ( V ˙ O 2 ) kinetics due to an enhanced oxidative energy turnover across the transition to exercise, which enables faster V ˙ O 2 kinetics and lesser disturbance of intracellular homeostasis ( Burnley et
Assessment of Gait Kinetics Using Triaxial Accelerometers
Emma Fortune, Melissa M.B. Morrow, and Kenton R. Kaufman
Repeated durations of dynamic activity with high ground reaction forces (GRFs) and loading rates (LRs) can be beneficial to bone health. To fully characterize dynamic activity in relation to bone health, field-based measurements of gait kinetics are desirable to assess free-living lower-extremity loading. The study aims were to determine correlations of peak vertical GRF and peak vertical LR with ankle peak vertical accelerations, and of peak resultant GRF and peak resultant LR with ankle peak resultant accelerations, and to compare them to correlations with tibia, thigh, and waist accelerations. GRF data were collected as ten healthy subjects (26 [19–34] years) performed 8–10 walking trials at velocities ranging from 0.19 to 3.05 m/s while wearing ankle, tibia, thigh, and waist accelerometers. While peak vertical accelerations of all locations were positively correlated with peak vertical GRF and LR (r 2 > .53, P < .001), ankle peak vertical accelerations were the most correlated (r 2 > .75, P < .001). All peak resultant accelerations were positively correlated with peak resultant GRF and LR (r 2 > .57, P < .001), with waist peak resultant acceleration being the most correlated (r 2 > .70, P < .001). The results suggest that ankle or waist accelerometers give the most accurate peak GRF and LR estimates and could be useful tools in relating physical activity to bone health.
Kinematics and Kinetics of Vigorous Head Shaking
James R. Funk, Richard A. Watson, Joseph M. Cormier, Herb Guzman, and Enrique Bonugli
Previous studies on neck muscle strength and motion have assumed or imposed varying constraints on the heads and bodies of the subjects. In this study, we asked 20 subjects to vigorously shake their heads 5−10 times in a completely unconstrained manner. The kinematics and kinetics of the head and neck were measured from video analysis and instrumentation mounted inside the mouth. Subjects shook their heads at self-selected tempos ranging from 1.9−4.7 Hz over a 20−91° range of motion. The motion of each subject’s head could be approximated by a fixed center of rotation that was typically located in the midcervical spine, but varied widely among subjects. Significant differences between men and women were observed. Peak head accelerations were low (4.3 ± 1.1 g and 250 ± 103 rad/s2 for men, 3.0 ± 0.9 g and 182 ± 58 rad/s2 for women) and estimated peak generated neck moments at C7/T1 were comparable to values reported in isometric neck strength studies (47 ± 14 N·m in extension and 22 ± 9 N·m in flexion for men, 25 ± 8 N·m in extension and 9 ± 7 N·m in flexion for women).
Kinetics of Badminton Lunges in Four Directions
Youlian Hong, Shao Jun Wang, Wing Kai Lam, and Jason Tak-Man Cheung
The lunge is the most fundamental skill in badminton competitions. Fifteen university-level male badminton players performed lunge maneuvers in four directions, namely, right-forward, left-forward, right-backward, and left-backward, while wearing two different brands of badminton shoes. The test compared the kinetics of badminton shoes in performing typical lunge maneuvers. A force plate and an insole measurement system measured the ground reaction forces and plantar pressures. These measurements were compared across all lunge maneuvers. The left-forward lunge generated significantly higher first vertical impact force (2.34 ± 0.52 BW) than that of the right-backward (2.06 ± 0.60 BW) and left-backward lunges (1.78 ± 0.44 BW); higher second vertical impact force (2.44 ± 0.51 BW) than that of the left-backward lunge (2.07 ± 0.38 BW); and higher maximum anterior-posterior shear force (1.48 ± 0.36 BW) than that of the left-backward lunge (1.18 ± 0.38 BW). Compared with other lunge directions, the left-forward lunge showed higher mean maximum vertical impact anterior-posterior shear forces and their respective maximum loading rates, and the plantar pressure at the total foot and heel regions. Therefore, the left-forward lunge is a critical maneuver for badminton biomechanics and related footwear research because of the high loading magnitude generated during heel impact.
Do Experienced Adolescent Competition Dancers Alter Landing Kinematics and Kinetics for Split Leaps or Center Leaps After Fatigue?
Zoie R. Mink and Amanda Esquivel
occurrence and reoccurrence are possible. 7 Most studies regarding kinematics and kinetics in dancers focus on the adult and professional dancer populations instead of youth dancers. 9 – 15 Along with this, the majority of previous research has utilized nondance-related jumps to quantify the effects of
The Effect of Backpack Load Carriage on the Kinetics and Kinematics of Ankle and Knee Joints During Uphill Walking
Jinkyu Lee, Yong-Jin Yoon, and Choongsoo S. Shin
shown, 29 but uphill walking can cause musculoskeletal pain and injuries to the body. 30 Therefore, several research groups have analyzed the effects of uphill walking on postural adaptations, 26 muscle activity, 31 kinematics, and joint kinetics. 31 , 32 However, the effects of
Children Who Are Overweight Display Altered Vertical Jump Kinematics and Kinetics From Children Who Are Not Overweight
Jeffrey C. Cowley, Steven T. McCaw, Kelly R. Laurson, and Michael R. Torry
exhibited by children who are overweight are not well documented. The purpose of this study was to compare the sagittal plane kinematics and kinetics of the ankle, knee, and hip joints during the countermovement vertical jump between children who are overweight and normal weight. It was hypothesized that
