scholarly journals Lower Extremity Stiffness in Collegiate Distance Runners Pre- and Post-Competition

2020 ◽  
Vol 71 (1) ◽  
pp. 69-77
Author(s):  
Jake P. Tavernite ◽  
Matthew F. Moran
Keyword(s):  
Ground Reaction Forces ◽  
Distance Runners ◽  
Countermovement Jump ◽  
Squat Jump ◽  
Leg Stiffness ◽  
Main Effect ◽  
Before And After ◽  
Reaction Forces ◽  
Cross Country ◽  
Post Hoc

AbstractPrevious evidence has suggested that there is a relationship between leg stiffness and improved running performance. The purpose of this investigation was to determine how leg stiffness of runners was influenced in the 24 and 48 hour period following a cross country race. Twenty-two collegiate cross-country runners (13 males, 9 females, 19.5 ± 1.4 yr) were recruited and participated in the study. Leg stiffness was assessed 24 hours before and after a race as well as 48 hours post-race. Three jumping protocols were conducted: 1) a static jump, 2) a countermovement jump, and 3) a vertical hopping test. Two embedded force plates (1000 Hz) were utilized to measure ground reaction forces for each test and a metronome was utilized to maintain hopping frequency (2.2 Hz). A significant main effect was found for a static jump, a countermovement jump and leg stiffness. Leg stiffness was significantly reduced 24 hours post-race (pre-race 36.84 kN·m-1, 24h post 33.11 kN·m-1, p < 0.05), but not 48 hours post-race (36.30 kN·m-1). No significant differences were found in post-hoc analysis for the squat jump, countermovement jump height and the eccentric utilization ratio. Following a cross-country race, leg stiffness significantly declined in a group of collegiate runners in the immediate 24 hours post-race, but returned to baseline 48 hours post-race. Sport scientists and running coaches may be able to monitor leg stiffness as a metric to properly prescribe training regiments.

scholarly journals Effects of Short-Term Plyometric Training on Agility, Jump and Repeated Sprint Performance in Female Soccer Players

2021 ◽  
Vol 18 (5) ◽  
pp. 2274
Author(s):  
Marcin Maciejczyk ◽  
Renata Błyszczuk ◽  
Aleksander Drwal ◽  
Beata Nowak ◽  
Marek Strzała
Keyword(s):  
Physical Performance ◽  
Sprint Performance ◽  
Soccer Players ◽  
Plyometric Training ◽  
Countermovement Jump ◽  
Short Term ◽  
Jump Performance ◽  
Squat Jump ◽  
Repeated Sprint ◽  
Before And After

The aim of the study was to determine the effects of short-term (4 weeks, twice a week: 8 sessions) plyometric training on agility, jump, and repeated sprint performance in female soccer players. The study comprised 17 females performing this sports discipline. The players were randomly divided into two groups: with plyometric training (PLY) and the control (CON). All players followed the same training program, but the PLY group also performed plyometric exercises. Tests used to evaluate physical performance were carried out immediately before and after PLY. After implementing the short PLY training, significant improvement in jump performance (squat jump: p = 0.04, ES = 0.48, countermovement jump: p = 0.009, ES = 0.42) and agility (p = 0.003, ES = 0.7) was noted in the PLY group. In the CON group, no significant (p > 0.05) changes in physical performance were observed. In contrast, PLY did not improve repeated sprint performance (p > 0.05) among female soccer players. In our research, it was shown that PLY can also be effective when performed for only 4 weeks instead of the 6–12 weeks typically applied.

Reduced prosthetic stiffness lowers the metabolic cost of running for athletes with bilateral transtibial amputations

2017 ◽  
Vol 122 (4) ◽  
pp. 976-984 ◽  
Author(s):  
Owen N. Beck ◽  
Paolo Taboga ◽  
Alena M. Grabowski
Keyword(s):  
Lower Limb ◽  
Metabolic Cost ◽  
Ground Reaction Forces ◽  
Metabolic Rates ◽  
Distance Running ◽  
Cost Of Transport ◽  
Leg Stiffness ◽  
Metabolic Costs ◽  
In Series ◽  
Reaction Forces

Inspired by the springlike action of biological legs, running-specific prostheses are designed to enable athletes with lower-limb amputations to run. However, manufacturer’s recommendations for prosthetic stiffness and height may not optimize running performance. Therefore, we investigated the effects of using different prosthetic configurations on the metabolic cost and biomechanics of running. Five athletes with bilateral transtibial amputations each performed 15 trials on a force-measuring treadmill at 2.5 or 3.0 m/s. Athletes ran using each of 3 different prosthetic models (Freedom Innovations Catapult FX6, Össur Flex-Run, and Ottobock 1E90 Sprinter) with 5 combinations of stiffness categories (manufacturer’s recommended and ± 1) and heights (International Paralympic Committee’s maximum competition height and ± 2 cm) while we measured metabolic rates and ground reaction forces. Overall, prosthetic stiffness [fixed effect (β) = 0.036; P = 0.008] but not height ( P ≥ 0.089) affected the net metabolic cost of transport; less stiff prostheses reduced metabolic cost. While controlling for prosthetic stiffness (in kilonewtons per meter), using the Flex-Run (β = −0.139; P = 0.044) and 1E90 Sprinter prostheses (β = −0.176; P = 0.009) reduced net metabolic costs by 4.3–4.9% compared with using the Catapult prostheses. The metabolic cost of running improved when athletes used prosthetic configurations that decreased peak horizontal braking ground reaction forces (β = 2.786; P = 0.001), stride frequencies (β = 0.911; P < 0.001), and leg stiffness values (β = 0.053; P = 0.009). Remarkably, athletes did not maintain overall leg stiffness across prosthetic stiffness conditions. Rather, the in-series prosthetic stiffness governed overall leg stiffness. The metabolic cost of running in athletes with bilateral transtibial amputations is influenced by prosthetic model and stiffness but not height. NEW & NOTEWORTHY We measured the metabolic rates and biomechanics of five athletes with bilateral transtibial amputations while running with different prosthetic configurations. The metabolic cost of running for these athletes is minimized by using an optimal prosthetic model and reducing prosthetic stiffness. The metabolic cost of running was independent of prosthetic height, suggesting that longer legs are not advantageous for distance running. Moreover, the in-series prosthetic stiffness governs the leg stiffness of athletes with bilateral leg amputations.

The Effects of Posture and Technique on Forces Experienced When Hanging Continuous Miner Cable

1993 ◽  
Vol 37 (10) ◽  
pp. 779-783 ◽  
Author(s):  
Sean Gallagher ◽  
Christopher A. Hamrick ◽  
Mark S. Redfern
Keyword(s):  
Injury Risk ◽  
Underground Mines ◽  
Ground Reaction Forces ◽  
Shear Forces ◽  
Lateral Shear ◽  
Continuous Miner ◽  
Underground Coal Mines ◽  
Reaction Forces ◽  
Post Hoc ◽  
Resultant Forces

Analysis of lost-time back injuries in underground coal mines indicates that handling continuous miner cable places workers at high risk of injury. Manual hanging of this type of cable is a common lifting task in underground mines. This study was performed to assess the ground reaction forces associated with hanging cable in various postures and employing different methods of securing the cable. Seven experienced coal miners (mean age: 41.4 years ± 2.1) performed a series of 12 cable hanging tasks. Independent variables included a set of six posture/vertical space constraint conditions (LIFTCOND), and two techniques of securing the cable to the ceiling (METHOD). The dependent variables consisted of ground reaction forces measured using two force plates. LIFTCOND ( F5.66 = 21.31, p < 0.0001) and METHOD ( F1,66 = 10.89, p < 0.005) both significantly affected the magnitude of the peak resultant forces generated during the tasks. Post hoc analysis indicated that kneeling postures resulted in significantly lower forces than stooping for the same ceiling heights. Greater forces were associated with higher lifting conditions, attributable in part to the fact that higher lifts require more cable to be hoisted. Forces were also increased when subjects twisted baling wire to secure the cable, as compared to hanging it on a hook. An interaction between LIFTCOND and METHOD was identified with lateral shear forces - stooping conditions where the subjects twisted the cable with wire resulted in higher lateral shear forces. Results of this study will be used to develop recommendations to reduce back injury risk when handling cable.

Sex and stride length impact leg stiffness and ground reaction forces when running with body borne load

2019 ◽  
Vol 86 ◽  
pp. 96-101 ◽  
Author(s):  
Nicholas J. Lobb ◽  
AuraLea C. Fain ◽  
Kayla D. Seymore ◽  
Tyler N. Brown
Keyword(s):  
Stride Length ◽  
Ground Reaction Forces ◽  
Leg Stiffness ◽  
Reaction Forces

The Effects of Uni- and Bilateral Fatigue on Postural and Power Tasks

2013 ◽  
Vol 29 (1) ◽  
pp. 44-48 ◽  
Author(s):  
Paulo H. Marchetti ◽  
Maria I.V. Orselli ◽  
Marcos Duarte
Keyword(s):  
Lower Limb ◽  
Healthy Subjects ◽  
Postural Sway ◽  
Center Of Pressure ◽  
Lower Limbs ◽  
Quiet Standing ◽  
Ground Reaction Forces ◽  
Before And After ◽  
Reaction Forces ◽  
The Mean

The aim of this study was to investigate the effects of unilateral and bilateral fatigue on both postural and power bipedal tasks. Ten healthy subjects performed two tasks: bipedal quiet standing and a maximal bipedal counter-movement jumping before and after unilateral (with either the dominant or nondominant lower limb) and bilateral (with both lower limbs) fatigue. We employed two force plates (one under each lower limb) to measure the ground reaction forces and center of pressure produced by subjects during the tasks. To quantify the postural sway during quiet standing, we calculated the resultant center of pressure (COP) speed and COP area of sway, as well as the mean weight distribution between lower limbs. To quantify the performance during the countermovement jumping, we calculated the jump height and the peak force of each lower limb. We observed that both unilateral and bilateral fatigue affected the performance of maximal voluntary jumping and standing tasks and that the effects of unilateral and bilateral fatigue were stronger in the dominant limb than in the nondominant limb during bipedal tasks. We conclude that unilateral neuromuscular fatigue affects both postural and power tasks negatively.

scholarly journals Spring-like leg behaviour, musculoskeletal mechanics and control in maximum and submaximum height human hopping

2011 ◽  
Vol 366 (1570) ◽  
pp. 1516-1529 ◽  
Author(s):  
Maarten F. Bobbert ◽  
L. J. Richard Casius
Keyword(s):  
Energy Expenditure ◽  
Muscle Activation ◽  
Mechanical Energy ◽  
Reaction Force ◽  
Ground Reaction Forces ◽  
Centre Of Mass ◽  
Leg Stiffness ◽  
Reaction Forces ◽  
And Control ◽  
The Relationship

The purpose of this study was to understand how humans regulate their ‘leg stiffness’ in hopping, and to determine whether this regulation is intended to minimize energy expenditure. ‘Leg stiffness’ is the slope of the relationship between ground reaction force and displacement of the centre of mass (CM). Variations in leg stiffness were achieved in six subjects by having them hop at maximum and submaximum heights at a frequency of 1.7 Hz. Kinematics, ground reaction forces and electromyograms were measured. Leg stiffness decreased with hopping height, from 350 N m −1 kg −1 at 26 cm to 150 N m −1 kg −1 at 14 cm. Subjects reduced hopping height primarily by reducing the amplitude of muscle activation. Experimental results were reproduced with a model of the musculoskeletal system comprising four body segments and nine Hill-type muscles, with muscle stimulation STIM( t ) as only input. Correspondence between simulated hops and experimental hops was poor when STIM( t ) was optimized to minimize mechanical energy expenditure, but good when an objective function was used that penalized jerk of CM motion, suggesting that hopping subjects are not minimizing energy expenditure. Instead, we speculated, subjects are using a simple control strategy that results in smooth movements and a decrease in leg stiffness with hopping height.

scholarly journals The effect of eight-week elastic walking exercise on the pattern of plantar pressure distribution in women with chronic low back pain during walking

2021 ◽  
Vol 42 (6) ◽  
pp. 713-721
Author(s):  
Farnaz Seify ◽  
Elahe Mamashli ◽  
AmirAli Jafarnejadgero ◽  
Mahrokh Dehghani ◽  
Mohsen Katanchi ◽  
...  
Keyword(s):  
Low Back Pain ◽  
Back Pain ◽  
Distribution Pattern ◽  
Plantar Pressure ◽  
Reaction Force ◽  
Ground Reaction Forces ◽  
Low Back ◽  
Main Effect ◽  
Reaction Forces ◽  
Experimental Group

Background: Training of elastic walking is a new method for elasticity in gait and correction of the distribution pattern of plantar pressure in patients with low back pain during gait. This study aimed to investigate the distribution pattern of plantar pressure during gait in women with low back pain following 8 weeks-training of elastic walking. Methods: The present study was quasi-experimental. In this research, 20 women with low back pain were divided into control (n=11) and experimental (n=9) groups. Subjects from the experimental group performed elastic gait training for 3 sessions per week for 8 weeks while the control group didn’t have any exercise program. The plantar pressure variables included the peak of vertical ground reaction forces, the time to peak of ground reaction forces, loading rate, the peak of plantar pressure on the ten foot regions, the peak of ground reaction forces on the ten foot regions, and displacement of the pressure center in two internal-external (copx) and anterior-posterior (copy) lines. The distribution pattern of plantar pressure during gait was recorded by a foot scan system (Sampling rate 300 Hz) in pre-training and post-training. Two-way ANOVA was used to analyze the data. The significance level was set at P < 0.05. Results: In the experimental group, the results of this study demonstrated lower peak vertical reaction force (FzMS component) during post-test compared with pre-test (P = 0.002). Moreover, findings showed that the main effect of group on peak pressure in the mid-foot region was significant (P = 0.011). The results showed no significant difference concerning the main effect of group, the main effect of time and effect, interaction time and group on peak vertical reaction force, displacement of pressure center, vertical loading rate, and walking stance time (P > 0.05). Conclusion: The findings of this study showed that training of elastic walking does not have a significant effect on stance time. Also, training of elastic walking in the experimental group reduced the peak vertical ground reaction force (FzMS component) during the post-test compared with the pre-test that can correct the walking pattern and improve the chronic low back pain.

scholarly journals Immediate Effect on Ground Reaction Forces Induced by Step Training Based on Discrete Skill during Gait in Poststroke Individuals: A Pilot Study

2020 ◽  
Vol 2020 ◽  
pp. 1-8
Author(s):  
Masanori Wakida ◽  
Koji Ohata ◽  
Yu Hashiguchi ◽  
Kimihiko Mori ◽  
Kimitaka Hase ◽  
...  
Keyword(s):  
Pilot Study ◽  
Walking Speed ◽  
Community Dwelling ◽  
Ground Reaction Forces ◽  
Clear Understanding ◽  
Walking Ability ◽  
Training Methods ◽  
Before And After ◽  
Reaction Forces ◽  
Response Phase

Background/Aim. Improving walking ability, especially the step-to-step transition control, is important in individuals after stroke. Although walking is a continuous skill, the discrete skills of gait, defined as movements with a clear beginning and end, may effectively modify walking performance. This pilot study shows the immediate effects of a discrete skill-based step training on ground reaction forces (GRFs) during gait in individuals with chronic hemiplegia following stroke. Methods. Twenty-two community-dwelling patients with chronic hemiplegia participated in this study. Eight participants performed only discrete-skill step training during the loading response phase, focusing on paretic hip extension movement (LR group). Another eight performed only discrete-skill step training during the preswing phase, focusing on paretic swing movement (PSw group). The remaining six were trained using both training methods, with at least 6 months in each group to washout the influence of previous training. Therefore, the final number of participants in each group was 14. The braking and propulsive forces of GRFs were measured during gait before and after 30 repetitions of the discrete-skill step training. Results. Although both groups showed a significant increase in stride length, walking speed was increased only in the LR group. The PSw group showed an increase in braking forces of both sides without any change in propulsion. In the LR group, paretic braking impulse did not change, while nonparetic propulsion increased. Conclusion. The discrete-skill step training during loading response phase induced an increase in nonparetic propulsion, resulting in increased walking speed. This study provides a clear understanding of immediate effects of the discrete-skill step training in patients with chronic stroke and helps improve interventions in long-term rehabilitation.

Force Measurements during Cross-Country Skiing

1987 ◽  
Vol 3 (4) ◽  
pp. 370-381 ◽  
Author(s):  
Paavo V. Komi
Keyword(s):  
Functional Significance ◽  
Force Platform ◽  
Ground Reaction Forces ◽  
Force Measurements ◽  
Experimental Conditions ◽  
Reaction Forces ◽  
Cross Country Skiing ◽  
Cross Country ◽  
Platform System ◽  
Component Force

To understand cross-country (X-C) siding it is important to record and identity forces of skis and poles separately and together. They both contribute to the forward progression, but their functional significance may be more complex than that of the ground reaction forces in running and walking. This report presents two methods to record forces on skis and poles during normal X-C skiing. A long force-platform system with four rows of 6-m long plates is placed under the snow track for recording of Fz and Fy forces of each ski and pole separately. This system is suitable especially for the study of diagonal technique under more strict experimental conditions. The second system consists of small lightweight Fz and Fy component force plates which are installed under the boot and binding. These plates can be easily changed from one ski to another, and telemetric recording allows free skiing over long distances and with different skiing techniques, including skating. The presentation emphasizes the integrated use of either system together with simultaneous cinematographic and electromyographic recordings.

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