Intensity- and muscle-specific fascicle behavior during human drop jumps

2007 ◽  
Vol 102 (1) ◽  
pp. 382-389 ◽  
Author(s):  
F. Sousa ◽  
M. Ishikawa ◽  
J. P. Vilas-Boas ◽  
P. V. Komi
Keyword(s):  
Length Change ◽  
Medial Gastrocnemius ◽  
Ground Contact ◽  
Contact Phase ◽  
Drop Jumps ◽  
Synergistic Muscles ◽  
Braking Phase ◽  
Whole Muscle ◽  
Specific Length

The present study was designed to examine fascicle-tendon interaction in the synergistic medial gastrocnemius (MG) and soleus (Sol) muscles during drop jumps (DJ) performed from different drop heights (DH). Eight subjects performed unilateral DJ with maximal rebounds on a sledge apparatus from different DH. During the exercises, fascicle lengths (using ultrasonography) and electromyographic activities were recorded. The results showed that the fascicles of the MG and Sol muscles behaved differently during the contact phase, but the whole muscle-tendon unit and its tendinous tissue lengthened before shortening in both muscles. The Sol fascicles also lengthened before shortening during the ground contact in all conditions. During the braking phase, the Sol activation increased with increasing DH. However, the amplitude of Sol fascicle lengthening was not dependent on DH during the same phase. In the MG muscle, the fascicles primarily shortened during the braking phase in the lower DH condition. However, in the higher DH conditions, the MG fascicles either behaved isometrically or were lengthened during the braking phase. These results suggest that the fascicles of synergistic muscles (MG and Sol) can behave differently during DJ and that, with increasing DH, there may be specific length change patterns of the fascicles of MG but not of Sol.

scholarly journals Assessing Plyometric Ability during Vertical Jumps Performed by Adults and Adolescents

Sports ◽  
2018 ◽  
Vol 6 (4) ◽  
pp. 132 ◽  
Author(s):  
Brandon Snyder ◽  
Shawn Munford ◽  
Chris Connaboy ◽  
Hugh Lamont ◽  
Shala Davis ◽  
...  
Keyword(s):  
Contact Time ◽  
Analysis Data ◽  
Adolescent Male ◽  
Ground Contact ◽  
Strength Index ◽  
Basketball Players ◽  
Contact Phase ◽  
Adult Men ◽  
Drop Jumps ◽  
Vertical Jumps

The purpose of this study was to compare different methods for assessing plyometric ability during countermovement (CMJ) and drop jumps (DJ) in a group of adults and adolescents. Ten resistance-trained adult men (age: 22.6 ± 1.6 years) and ten adolescent male basketball players (age: 16.5 ± 0.7 years) performed a CMJ and a DJ from a height of 0.40 m. Jump height (JH), contact time, normalized work (WNORM), and power output (PONORM) during the absorption and propulsion phases were calculated from force platforms and 3-D motion analysis data. Plyometric ability was assessed using the modified reactive strength index (RSIMOD during CMJ) and the reactive strength index (RSI during DJ) as well as three indices using propulsion time, propulsion work (PWI), and propulsion power. Adults jumped significantly higher than adolescents (mean difference [MD]: 0.05 m) while JH (MD: 0.05 m) and ground contact time (MD: 0.29 s) decreased significantly from CMJ to DJ. WNORM (MD: 4.2 J/kg) and PONORM (MD: 24.2 W/kg) during the absorption phase of CMJ were significantly less than these variables during the propulsion phases of the jumps. The reactive strength index variants increased significantly from the CMJ to DJ (MD: 0.23) while all other plyometric indices decreased significantly. Neither RSIMOD nor RSI contributed significantly to the prediction of JH during CMJ and DJ, respectively, while PWI was able to explain ≥68% of the variance in JH. Variants of the reactive strength index do not reflect the changes in mechanical variables during the ground contact phase of CMJ and DJ and may not provide an accurate assessment of plyometric ability during different vertical jumps.

Interaction between fascicle and tendinous tissues in short-contact stretch-shortening cycle exercise with varying eccentric intensities

2005 ◽  
Vol 99 (1) ◽  
pp. 217-223 ◽  
Author(s):  
M. Ishikawa ◽  
E. Niemelä ◽  
P. V. Komi
Keyword(s):  
Vastus Lateralis ◽  
Reaction Force ◽  
Flight Time ◽  
Medial Gastrocnemius ◽  
Elastic Recoil ◽  
Fascicle Length ◽  
Short Contact ◽  
Drop Jumps ◽  
Braking Force ◽  
Braking Phase

The interaction between fascicle and tendinous tissues (TT) in short-contact drop jumps (DJ) with three different drop heights [low (Low), optimal (OP), and high (High)] was examined with 11 subjects. The ground reaction force (F z) and ankle and knee joint angles were measured together with real-time ultrasonography (fascicle length) and electromyographic activities of the medial gastrocnemius (MG) and vastus lateralis (VL) muscles during the movement. With increasing drop height, the braking force and flight time increased from Low to OP ( P < 0.05). In High, the braking force increased but the flight time decreased compared with OP ( P < 0.05). During contact of Low and OP conditions, the length of muscle-tendon unit and TT underwent lengthening before shortening in both MG and VL muscles. However, the two muscles differed in the fascicle behaviors. The MG fascicles behaved isometrically or shortened, and the VL fascicles underwent lengthening before shortening during contact. In High, the TT lengthening in both muscles decreased compared with OP ( P < 0.05). The rapid stretch occurred in the MG fascicles but not in VL fascicles during the braking phase. The elastic recoil ratio decreased in both muscles with increasing the intensity during DJ. These findings demonstrated that TT underwent lengthening before shortening during DJ. However, the efficacy of elastic recoil decreased with increasing the drop intensity. The effective catapult action in TT can be limited by the drop intensity. In addition, the measured muscles behaved differently during DJ, providing evidence that each muscle may have a specific means of fascicle-TT interaction.

The role of the stretch reflex in the gastrocnemius muscle during human locomotion at various speeds

2007 ◽  
Vol 103 (3) ◽  
pp. 1030-1036 ◽  
Author(s):  
M. Ishikawa ◽  
P. V. Komi
Keyword(s):  
Stretch Reflex ◽  
High Speed ◽  
Stance Phase ◽  
Gastrocnemius Muscle ◽  
Human Locomotion ◽  
Medial Gastrocnemius ◽  
Ground Contact ◽  
Fascicle Length ◽  
Braking Phase

In the present study, the fascicle length ( Lfa) of the human medial gastrocnemius (MG) muscle was monitored to evaluate possible input from the short-latency stretch reflex (SLR) during the stance phase of running and to examine its timing at various running speeds. Eight subjects ran at 2.0, 3.5, 5.0, and 6.5 m/s. The Lfa was measured with the high-speed ultrasound fascicle scanning together with kinematics and myoelectrical activities. The amplitudes and onset latency of SLR activities were determined. During ground contact, the sudden MG fascicle stretch occurred during the early contact at all running speeds. This was followed by the fascicle shortening. The timing of fascicle stretch depended on running speed and type of foot contact. In slower speed conditions (2.0, 3.5, 5 m/s), the MG fascicle stretch and the corresponding SLR activities occurred during the middle of the braking phase. In fast-speed running (6.5 m/s), however, the MG fascicle stretch occurred later compared with the lower speed. The corresponding SLR activities occurred significantly later at the end of the braking phase. In addition to the clear demonstration of the different timings of SLR in MG during ground contact of running, the results imply that the role of the MG SLR during the stance phase of running can be different between fast- and slow-speed running conditions.

Biomechanics Differ for Individuals With Similar Self-Reported Characteristics of Patellofemoral Pain During a High-Demand Multiplanar Movement Task

2020 ◽  
pp. 1-10
Author(s):  
Matthew K. Seeley ◽  
Seong Jun Son ◽  
Hyunsoo Kim ◽  
J. Ty Hopkins
Keyword(s):  
Ground Reaction Force ◽  
Injury Risk ◽  
Reaction Force ◽  
Patellofemoral Pain ◽  
Joint Torque ◽  
Whole Body ◽  
Ground Contact ◽  
High Demand ◽  
Contact Phase ◽  
Hip Extension

Context: Patellofemoral pain (PFP) is often categorized by researchers and clinicians using subjective self-reported PFP characteristics; however, this practice might mask important differences in movement biomechanics between PFP patients. Objective: To determine whether biomechanical differences exist during a high-demand multiplanar movement task for PFP patients with similar self-reported PFP characteristics but different quadriceps activation levels. Design: Cross-sectional design. Setting: Biomechanics laboratory. Participants: A total of 15 quadriceps deficient and 15 quadriceps functional (QF) PFP patients with similar self-reported PFP characteristics. Intervention: In total, 5 trials of a high-demand multiplanar land, cut, and jump movement task were performed. Main Outcome Measures: Biomechanics were compared at each percentile of the ground contact phase of the movement task (α = .05) between the quadriceps deficient and QF groups. Biomechanical variables included (1) whole-body center of mass, trunk, hip, knee, and ankle kinematics; (2) hip, knee, and ankle kinetics; and (3) ground reaction forces. Results: The QF patients exhibited increased ground reaction force, joint torque, and movement, relative to the quadriceps deficient patients. The QF patients exhibited: (1) up to 90, 60, and 35 N more vertical, posterior, and medial ground reaction force at various times of the ground contact phase; (2) up to 4° more knee flexion during ground contact and up to 4° more plantarflexion and hip extension during the latter parts of ground contact; and (3) up to 26, 21, and 48 N·m more plantarflexion, knee extension, and hip extension torque, respectively, at various times of ground contact. Conclusions: PFP patients with similar self-reported PFP characteristics exhibit different movement biomechanics, and these differences depend upon quadriceps activation levels. These differences are important because movement biomechanics affect injury risk and athletic performance. In addition, these biomechanical differences indicate that different therapeutic interventions may be needed for PFP patients with similar self-reported PFP characteristics.

Scratch responses in normal cats: hindlimb kinematics and muscle synergies

1990 ◽  
Vol 64 (6) ◽  
pp. 1653-1667 ◽  
Author(s):  
P. C. Kuhta ◽  
J. L. Smith
Keyword(s):  
Muscle Activity ◽  
Knee Flexion ◽  
Knee Extensor ◽  
Head Movements ◽  
Medial Gastrocnemius ◽  
Emg Activity ◽  
Circular Path ◽  
Contact Phase ◽  
Ankle Joints ◽  
Flexor Muscles

1. Scratch responses evoked by a tactile stimulus applied to the outer ear canal were characterized in nine adult cats. Chronic electromyographic (EMG) electrodes were surgically implanted in selected flexor and extensor muscles of the hip, knee, and ankle joints to determine patterns of muscle activity during scratching. In some trials EMG records were synchronized with kinematic data obtained by digitizing high-speed cine film, and in one cat, medial gastrocnemius (MG) tendon forces were recorded along with EMG. For analysis the response was divided into three components: the approach, cyclic, and return periods. Usually scratch responses were initiated with the cat in a sitting position, but in some trials the animal initiated the response from a standing or lying posture. 2. During the approach period the hindlimb ipsilateral to the stimulated ear was lifted diagonally toward the head by a combination of hip and ankle flexion with knee extension. Hindlimb motions during the approach period were associated with sustained EMG activity in hip-flexor, knee-extensor (occasionally), and ankle-flexor muscles. Initial hindlimb motions were typically preceded by head movements toward the hindpaw, and at the end of the approach period, the head was tilted downward with the stimulated pinna lower than the contralateral ear. During the return period movements were basically the reverse of the approach period, with the hindpaw returning to the ground and the head moving away from the hindlimb. 3. During the cyclic period the number of cycles per response varied widely from 1 to 60 cycles with an average of 13 cycles, and cycle frequency ranged from 4 to 8 cycles/s, with a mean of 5.6 cycles/s. During each cycle the paw trajectory followed a fairly circular path, and the cycle was defined by three phases: precontact, contact, and postcontact. On average the contact phase occupied approximately 50% of the cycle and was characterized by extensor muscle activity and extension at the hip, knee, and ankle joints. The hindpaw contacted the pinna or neck at the base of the pinna throughout the contact phase, and paw contact typically resulted in a rostral motion of the head as the hindlimb extended. 4. The postcontact phase constituted approximately 24% of scratch cycle and was usually initiated by the onset of knee flexion. Ankle and then hip flexion followed knee flexion, and flexor muscles were active during the postcontact phase as the paw was withdrawn from the head. The precontact phase constituted approximately 26% of scratch cycle and was initiated by knee joint extension and knee-extensor activity.(ABSTRACT TRUNCATED AT 400 WORDS)

Activation of type-identified motor units during centrally evoked contractions in the cat medial gastrocnemius muscle. III. Muscle-unit force modulation

1996 ◽  
Vol 75 (1) ◽  
pp. 51-59 ◽  
Author(s):  
K. E. Tansey ◽  
A. K. Yee ◽  
B. R. Botterman
Keyword(s):  
Firing Rate ◽  
Motor Unit ◽  
Muscle Force ◽  
Motor Units ◽  
Medial Gastrocnemius ◽  
Rate Variation ◽  
Unit Force ◽  
Rate Modulation ◽  
Force Modulation ◽  
Whole Muscle

1. The aim of this study was to examine the extent of muscle-unit force modulation due to motoneuron firing-rate variation in type-identified motor units of the cat medial gastrocnemius (MG) muscle, and to investigate the contribution of muscle-unit force modulation to whole-muscle force regulation. The motoneuron discharge patterns recorded from 8 pairs of motor units during 12 smoothly graded muscle contractions evoked by stimulation of the mesencephalic locomotor region (MLR) were used to reactivate those units in isolation to estimate what their force profiles would have been like during the evoked whole-muscle contractions. 2. For most motor units, muscle-unit force modulation was similar to motoneuron firing-rate modulation, in that muscle-unit force increased over a limited range (120-600 g) of increasing whole-muscle tension and was then maintained at a near maximal (> 70%) output level as muscle force continued to rise. Most muscle units also decreased their force outputs over a slightly larger range of declining whole-muscle force before relaxing. This second finding was best explained by the counterclockwise hysteresis recorded in the motor units' frequency-tension (f-t) relationships. 3. In those instances when whole-muscle force fluctuated just above the recruitment threshold of a motor unit, a substantial percentage (10-25%) of the change in whole-muscle force could be accounted for by force modulation in that motor unit alone. This finding suggested that few motor units in the pool were simultaneously simultaneously undergoing force modulation. To evaluate this possibility, the extent of parallel muscle-unit force modulation within the 8 pairs of simultaneously active motor units was evaluated. As with parallel motoneuron firing-rate modulation, the extent of parallel muscle-unit force modulation was limited to unit pairs of the same physiological type and recruitment threshold. In several instances, pairs of motor units displayed parallel motoneuron firing-rate modulation but did not show parallel muscle-unit force modulation because of the nature of the motor units' f-t relationships. 4. The limited extent of parallel muscle-unit force modulation seen in these experiments implies that the major strategy for force modulation in the cat MG muscle, involving contractions estimated to reach 30-40% of maximum, may be motor-unit recruitment rather than motor-unit firing-rate variation with resulting force modulation. Given, however, that the majority of motor units are already recruited at these output levels (< 40%), it is proposed that motor-unit firing-rate variation with resulting force modulation may take over as the major muscle force modulating strategy at higher output levels.

Rises in whole muscle passive tension of mammalian muscle after eccentric contractions at different lengths

2003 ◽  
Vol 95 (3) ◽  
pp. 1224-1234 ◽  
Author(s):  
N. P. Whitehead ◽  
D. L. Morgan ◽  
J. E. Gregory ◽  
U. Proske
Keyword(s):  
Isometric Tension ◽  
The Other ◽  
Medial Gastrocnemius ◽  
Eccentric Contractions ◽  
Passive Tension ◽  
Active Length ◽  
Before And After ◽  
Two Factors ◽  
In Series ◽  
Whole Muscle

This is a report of experiments carried out on the medial gastrocnemius muscle of the anesthetized cat, investigating the effects of eccentric contractions carried out at different muscle lengths on the passive and active length-tension relationships. In one series of experiments, the motor supply to the muscle was divided into three approximately equal parts; in the other, whole muscles were used. Fifty eccentric contractions were carried out over different regions of the active length-tension curve for each partial or whole muscle. Active and passive length-tension curves were measured before and after the eccentric contractions. When eccentric contractions were carried out at longer lengths, there was a larger shift of the optimum length for active tension in the direction of longer muscle lengths and a larger fall in peak isometric tension. Passive tension was higher immediately after the eccentric contractions, and if the muscle was left undisturbed for 40 min, it increased further to higher values, particularly after contractions at longer lengths. A series of 20 passive stretches of the same speed and amplitude and covering the same length range as the active stretches, reduced the passive tension which redeveloped over a subsequent 40-min period. It is hypothesized that there are two factors influencing the level of passive tension in a muscle after a series of eccentric contractions. One is injury contractures in damaged muscle fibers tending to raise passive tension; the other is the presence of disrupted sarcomeres in series with still-functioning sarcomeres tending to reduce it.

scholarly journals An Approach for Simulation of the Muscle Force Modeling It by Summation of Motor Unit Contraction Forces

2013 ◽  
Vol 2013 ◽  
pp. 1-10 ◽  
Author(s):  
Rositsa Raikova ◽  
Hristo Aladjov ◽  
Jan Celichowski ◽  
Piotr Krutki
Keyword(s):  
Muscle Force ◽  
Cumulative Effect ◽  
Motor Units ◽  
Medial Gastrocnemius ◽  
Size Principle ◽  
Firing Patterns ◽  
Force Modeling ◽  
The Individual ◽  
Whole Muscle ◽  
Medial Gastrocnemius Muscle

Muscle force is due to the cumulative effect of repetitively contracting motor units (MUs). To simulate the contribution of each MU to whole muscle force, an approach implemented in a novel computer program is proposed. The individual contraction of an MU (the twitch) is modeled by a 6-parameter analytical function previously proposed; the force of one MU is a sum of its contractions due to an applied stimulation pattern, and the muscle force is the sum of the active MUs. The number of MUs, the number of slow, fast-fatigue-resistant, and fast-fatigable MUs, and their six parameters as well as a file with stimulation patterns for each MU are inputs for the developed software. Different muscles and different firing patterns can be simulated changing the input data. The functionality of the program is illustrated with a model consisting of 30 MUs of rat medial gastrocnemius muscle. The twitches of these MUs were experimentally measured and modeled. The forces of the MUs and of the whole muscle were simulated using different stimulation patterns that included different regular, irregular, synchronous, and asynchronous firing patterns of MUs. The size principle of MUs for recruitment and derecruitment was also demonstrated using different stimulation paradigms.

Application of Center-of-Pressure Data to Indicate Rearfoot Inversion-Eversion in Shod Running

2006 ◽  
Vol 96 (4) ◽  
pp. 305-312 ◽  
Author(s):  
Sharon J. Dixon
Keyword(s):  
Range Of Motion ◽  
Center Of Pressure ◽  
Correlation Coefficients ◽  
Ground Contact ◽  
Pressure Data ◽  
Contact Phase ◽  
Movement Data ◽  
Versus Peak ◽  
Rearfoot Eversion ◽  
Selection Of

Although pressure plates are used to help in the selection of appropriate footwear for runners, evidence relating aspects of pressure data to movement is lacking. A study was conducted to investigate whether center-of-pressure (COP) data obtained for shod running could be used to indicate the amount of rearfoot eversion. It was hypothesized that subjects exhibiting high rearfoot eversion during the initial ground contact phase of running would also show a large lateral-to-medial deviation in the COP. Pressure plate and rearfoot movement data were collected for 33 subjects. The COP was characterized using the lateral-to-medial deviation of the COP during the eversion phase of ground contact. Correlation coefficients were determined for COP deviation versus rearfoot range of motion and versus peak rearfoot eversion (P &lt; .05). In addition, subjects were grouped as high, moderate, or low pronators, and analysis of variance was used to test whether there were significant differences in COP deviation for these three groups (P &lt; .05). The COP deviation was found to have a low correlation with rearfoot range of motion (R = 0.46; P &lt; .05) and with peak rearfoot eversion (R = .54; P &lt; .05). High pronators had significantly higher COP deviation than the medium- and low-pronation groups (P &lt; .05). These findings support the use of COP deviation to detect high pronation. However, caution is advised in using the COP to indicate absolute rearfoot eversion. (J Am Podiatr Med Assoc 96(4): 305–312, 2006)

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