Footstrike pattern has received increased attention within the running community because there is... more Footstrike pattern has received increased attention within the running community because there is a common belief that forefoot strike running (FFS) is more advantageous (i.e., improve performance and reduce running injuries) than rearfoot strike running (RFS) in distance running. Literature reports suggest greater knee joint flexion magnitude and initial knee angle during stance in FFS compared with RFS running We examined the EMG activation of the triceps surae muscles during an acute transition from RFS to FFS strike. We tested the hypothesis that due to larger knee flexion in FFS the gastrocnemius muscles possibly decrease their EMG activity because muscle fascicles operate under unfavorable conditions. Fourteen competitive healthy middle- and long-distance runners who were habitual RFS runners ran on a treadmill at three speeds: 12, 14, and 16 km·h-1. Each running speed was performed with both FFS and RFS patterns. Lower limb kinematics in the sagittal plane and normalized elec...
Purpose The multidimensional role of hamstring muscle group strength in athletic performance and ... more Purpose The multidimensional role of hamstring muscle group strength in athletic performance and injury prevention is well documented, and nordic hamstring exercise (NHE) is a popular method for the development of hamstring strength. Our aim was to examine the EMG characteristics of the eccentric NHE as well as the effects of long-term eccentric NHE training on muscle strength and vertical jump performance in 10- to 11-year-old female handball players. Methods Players from the same handball team were randomly assigned to an eccentric NHE training (13 players) or a control group (10 players). Both groups continued their regular handball training routine, but the NHE group performed additional eccentric NHE exercises once or twice a week, with progressively increasing volume, over 20 weeks. To test training effects, countermovement jump (CMJ) height, eccentric hamstring impulse, peak torque, and angle of peak torque were evaluated before, during and after the training period. In the p...
Based on the current literature, the link between Achilles tendon moment arm length and running e... more Based on the current literature, the link between Achilles tendon moment arm length and running economy is not well understood. Therefore, the aim of this study was to further investigate the connection between Achilles tendon moment arm and running economy and the influence of Achilles tendon moment arm on the function of the plantarflexor muscle-tendon unit during running.Ten male competitive marathon runners volunteered for this study. The participants ran on a treadmill at two running speeds: 3 and 3.5 m s−1. During running the oxygen consumption, lower leg kinematics, electrical activity of plantar flexor muscles, and fascicle behavior of the lateral gastrocnemius were measured simultaneously. On the second occasion, an MRI scan of the right leg was taken and used to estimate the Achilles tendon moment arm length.There was a negative correlation between running economy and the body height normalized moment arm length at both selected speeds (r = −0.68, P = 0.014 and r = −0.70, ...
Introduction. In human locomotion every external condition generates a strategy. The aim of this ... more Introduction. In human locomotion every external condition generates a strategy. The aim of this study is to analyze the kinematics parameters and to indentify the changes in movement pattern and muscle activity of race-walkers (RW). Methods. Twelve elite RW have race walking on a treadmill for 5 minutes each slope (0, 2 and 7%) in iso-efficiency speed (IES1) with heart rate and sEMG on leg muscles constantly monitored. Digital cameras (210 Hz) were used to record; Dartfish 5.5Pro was used to perform a 2D video analysis, while for statistical analysis was used Anova. (1) The IES (km/h) for each subject at 0% grade was the average speed during the best performance in the 10000 m race, minus 1 km/h, which corresponds to the ~50% Vo2MAX and requires an energy cost (Cw0) of 5.0 J/m/kg according to previous studies (Di Prampero 1986). Moreover, according to previous data (Minetti et al. 2002) the increase of Cw as a function of ground slope is: 0.15 * slope (%) + Cw0. We calculated for each ground slope the IES at which the Vo2 was equal to the oxygen consumption during level race walking using the following equation: Vo2= (Cw0/21(J/m) * (IES0/0.06 (m/min)) IES= (Vo2 * 21 * 0.06)/(0.15(Cw) * slope (%) + (Cw0)) Results IES, step length (SL) and frequency (SF) decrease as a function of the increasing slope: IES0 12.5 \u2013 IES2 11.8 \u2013 IES7 10.3; SL= (0-2%= -3.71%, n.s.; 0-7%= -12.23%, p<0.001); SF= (0-2%= -2.38%, n.s.; 0-7%= -6.07%, p<0.01). The contact time (CT) and heart rate (HR) increase at the increasing slope: CT= (0-2%= 2.46%, n.s.; 0-7%= 6.56%, p<0.01); HR= (0-2%= 0.62%, n.s.; 0-7%= 3.25%, p<0.05). The sEMG activity was reduced at the increasing slope in: tibialis anterior (0-2%= 22.49%, p<0.0001; 0-7%= 41.18%, p<0.0001); rectus femoris (0-2%= 15.35%, p<0.0001; 0-7%= 29.13%, p<0.0001). While the sEMG activity was increased in this muscles: vastus lateralis (0-2%= 22.95%, p<0.0001; 0-7%= 31.15%, p<0.0001); gastrocnemius medialis (0-2%= 21.40%, p<0.001; 0-7%= 48.37%, p<0.0001); biceps femoris (0-2%= 190.78%, p<0.0001; 0-7%= 201.37%, p<0.0001). Discussion. These results provide the resultant of the real mechanical work in different slopes without increasing energetic cost, validating the equation to calculate the speed in RW only at IES between zero and 2% gradient. While for higher gradient levels the procedure used in this study seems to overestimate the speed, probably due to the different biomechanics between walking (Minetti et al., 2002) and race walking. References Di Prampero PE. The energy cost of human locomotion on land and in water. (1986). Int J Sports Med, 7 (2), 55-72. Minetti AE, Moia C, Roi GS, Susta D, Ferretti G. Energy cost of walking and running at extreme uphill and downhill slopes. (2002). J Appl Physiol, 93(3),1039-1046
Flexor hallucis longus (FHL) muscle has several functions, including plantarflexion of the ankle,... more Flexor hallucis longus (FHL) muscle has several functions, including plantarflexion of the ankle, flexion of the big toe and support of the medial longitudinal arch. To date, only a few studies have used non-invasive methods to examine FHL behavior during real-life movements, although the proper functioning of this muscle may be important to increase sport performance, the altered FHL function may contribute to the susceptibility to Achilles tendinopathy and the function of FHL is altered in other clinical conditions such as flatfoot. FHL seems to be multifunctional but other active and passive structures also contribute to the same functions. Because of the multifunctionality of the foot structures and FHL itself, it is hard to define the main role of FHL during certain kinds of tasks and real-life movements. It is also more difficult to determine how morphological changes in the FHL affect its function. In this review we summarise studies that have examined FHL function focusing particularly on functionally relevant in vivo measurements, and possible effects of FHL anatomical and functional changes. Furthermore we make suggestions regarding studies that are needed in the future to fill the gaps in our knowledge about the role of FHL.peerReviewe
The human ankle joint and plantar flexor muscle–tendon unit play an important role in endurance r... more The human ankle joint and plantar flexor muscle–tendon unit play an important role in endurance running. It has been assumed that muscle and tendon interactions and their biomechanical behaviours depend on their morphological and architectural characteristics. We aimed to study how plantar flexor muscle characteristics influence marathon running performance and to determine whether there is any difference in the role of the soleus and gastrocnemii. The right lower leg of ten male distance runners was scanned with magnetic resonance imagining. The cross-sectional areas of the Achilles tendon, soleus, and lateral and medial gastrocnemius were measured, and the muscle volumes were calculated. Additional ultrasound scanning was used to estimate the fascicle length of each muscle to calculate the physiological cross-sectional area. Correlations were found between marathon running performance and soleus volume (r = 0.55, p = 0.048), soleus cross-sectional area (r = 0.57, p = 0.04), soleus...
Aims The aim of this study was to examine the effects of gender on the relationship between Funct... more Aims The aim of this study was to examine the effects of gender on the relationship between Functional Movement Screen (FMS) and treadmill-based gait parameters. Methods Twenty elite junior athletes (10 women and 10 men) performed the FMS tests and gait analysis at a fixed speed. Between-gender differences were calculated for the relationship between FMS test scores and gait parameters, such as foot rotation, step length, and length of gait line. Results Gender did not affect the relationship between FMS and treadmill-based gait parameters. The nature of correlations between FMS test scores and gait parameters was different in women and men. Furthermore, different FMS test scores predicted different gait parameters in female and male athletes. FMS asymmetry and movement asymmetries measured by treadmill-based gait parameters did not correlate in either gender. Conclusion There were no interactions between FMS, gait parameters, and gender; however, correlation analyses support the id...
Journal of Strength and Conditioning Research, 2016
Matlák, J, Tihanyi, J, and Rácz, L. Relationship between reactive agility and change of direction... more Matlák, J, Tihanyi, J, and Rácz, L. Relationship between reactive agility and change of direction speed in amateur soccer players. J Strength Cond Res 30(6): 1547-1552, 2016-The aim of the study was to assess the relationship between reactive agility and change of direction speed (CODS) among amateur soccer players using running tests with four directional changes. Sixteen amateur soccer players (24.1 ± 3.3 years; 72.4 ± 7.3 kg; 178.7 ± 6 cm) completed CODS and reactive agility tests with four changes of direction using the SpeedCourt™ system (Globalspeed GmbH, Hemsbach, Germany). Countermovement jump (CMJ) height and maximal foot tapping count (completed in 3 seconds) were also measured with the same device. In the reactive agility test, participants had to react to a series of light stimuli projected onto a screen. Total time was shorter in the CODS test than in the reactive agility test (p < 0.001). Nonsignificant correlations were found among variables measured in the CODS, reactive agility, and CMJ tests. Low common variance (r = 0.03-0.18) was found between CODS and reactive agility test variables. The results of this study underscore the importance of cognitive factors in reactive agility performance and suggest that specific methods may be required for training and testing reactive agility and CODS.
The Journal of sports medicine and physical fitness, 2001
Although the plyometric training has proved its efficiency, it remains generally unknown whether ... more Although the plyometric training has proved its efficiency, it remains generally unknown whether a limited amount of plyometric training could improve movements in subjects who already demonstrate high level of performance. Three different training regimens were performed in order to study effects of plyometric training on elite junior basketball players. While control group (CG) participated only in the regular midseason training activity, another two groups performed a limited amount of plyometric training employing drop jumps from the height of either 50 cm (EG-50) or 100 cm (EG-100). The height of the maximal vertical jump (CMJ), as well as the maximal voluntary force (F) and the rate of force development (RFD) of hip and knee extensors were tested prior to and after the training. An increase in CMJ (4.8 and 5.6 cm in EG-50 and EG-100, respectively), as well as in F of hip extensors and RFD of knee extensors was observed in both experimental groups, while no significant changes ...
Journal of Strength and Conditioning Research, 2014
We examined the susceptibility of fast and slow twitch muscle fibers in the quadriceps muscle to ... more We examined the susceptibility of fast and slow twitch muscle fibers in the quadriceps muscle to eccentric exercise-induced muscle damage. Nine healthy men (age: 22.5 ± 1.6 years) performed maximal eccentric quadriceps contractions at 120°·s-1 over a 120° of knee joint range of motion for 6 consecutive days. Biopsies were taken from the vastus lateralis muscle before repeated bouts of eccentric exercise on the third and seventh day. Immunohistochemical procedures were used to determine fiber composition and fibronectin activity. Creatine kinase (CK) and lactate dehydrogenase (LDH) were determined in serum. Average torque was calculated in each day for each subject. Relative to baseline, average torque decreased 37.4% till day 3 and increased 43.0% from the day 3 to day 6 (p < 0.001). Creatine kinase and LDH were 70.6 and 1.5 times higher on day 3 and 75.5 and 1.4 times higher on day 6. Fibronectin was found in fast fibers in subjects with high CK level on day 3 and 7 after exercise, but on day 7, fibronectin seemed in both slow and fast fibers except in muscles of 2 subjects with high fast fiber percentage. Peak torque and muscle fiber-type composition measured at baseline showed a strong positive association on day 3 (r = 0.76, p < 0.02) and strong negative association during recovery between day 3 and day 6 (r = -0.76, p < 0.02), and day 1 and day 6 (r = 0.84, p < 0.001). We conclude that the damage of fast fibers preceded the damage of slow fibers, and muscles with slow fiber dominance were more susceptible to repeated bouts of eccentric exercise than fast fiber dominance muscles. The data suggest that the responses to repeated bouts of eccentric exercise are fiber-type-dependent in the quadriceps muscle, which can be the basis for the design of individualized strength training protocols.
Journal of Strength and Conditioning Research, 2013
To determine the acute task and stretch-load dependency of neuromuscular impairments after muscle... more To determine the acute task and stretch-load dependency of neuromuscular impairments after muscle-damaging exercises, we examined the magnitude of strength deficits in isometric and stretch-shortening cycle (SSC) contractions after a single bout of exercise. Ten trained men performed 90 unilateral isokinetic eccentric-concentric knee extensions on a dynamometer. Plasma creatine kinase activity, muscle soreness, maximal isometric torque, short-range stiffness, and peak torque in the eccentric phase of the SSC contraction at 3 stretch-loads (120, 150, and 180 J) were determined in the quadriceps before and 24 hours after exercise. During SSC, positive mechanical work and efficiency were also calculated. Creatine kinase and soreness increased at 24 hours (p < 0.05). In each of the 3 stretch-load conditions, muscle damage affected short-range stiffness less than isometric and peak SSC torque (p < 0.05), providing evidence for a selective impairment in contractile function after muscle damage. With greater SSC stretch-load peak, SSC torque deficit increased linearly, whereas short-range stiffness deficit was unaffected. Efficiency declined only at the 180-J condition (p < 0.05) as a result of decreased positive work (p < 0.05). It was concluded that intense exercise produced microtrauma in the muscle, and a selective loss of force generating capacity, which suggests greater damage to the contractile machinery. Practitioners may expect greater acute impairment of force generation in movements that use large loads in their daily training drills. However, altered knee flexion strategy during SSC may compensate for the force deficit, preserving mechanical efficiency at smaller stretch-loads.
Leg extensor muscle characteristics, running speed and serum testosterone were studied in sixteen... more Leg extensor muscle characteristics, running speed and serum testosterone were studied in sixteen males and twelve female sprinters. The rise of center of gravity was measured during squat jumps executed without (SJ) and with extra loads (SJbm), counter movement jump (CMJ) and continuous jumping (CJ) for 5 s. Nine females and nine males performed also half-squat exercises with extra loads ranging from 50% to 200% of the subject's body mass (bm). Average mechanical power (P), force (F) and velocity (v) were calculated and measured during half-squat exercises using the Ergopower®. Total serum testosterone (TT) was determined in venous blood. In women, 60 m dash, SJ, CMJ and CJ performances were significantly lower (P<0.001) than men. Gender differences were not found in F during half-squat exercises and in SJbm. Women demonstrated significantly higher ratios CMJ:SJ and CJ:SJ than men. With loads 50-100 % of bm men demonstrated greater v and P than women. It was suggested that high testosterone level in men might be a factor ensured superiority in explosive power and speed, but not in muscle strength adjusted to body mass.
Footstrike pattern has received increased attention within the running community because there is... more Footstrike pattern has received increased attention within the running community because there is a common belief that forefoot strike running (FFS) is more advantageous (i.e., improve performance and reduce running injuries) than rearfoot strike running (RFS) in distance running. Literature reports suggest greater knee joint flexion magnitude and initial knee angle during stance in FFS compared with RFS running We examined the EMG activation of the triceps surae muscles during an acute transition from RFS to FFS strike. We tested the hypothesis that due to larger knee flexion in FFS the gastrocnemius muscles possibly decrease their EMG activity because muscle fascicles operate under unfavorable conditions. Fourteen competitive healthy middle- and long-distance runners who were habitual RFS runners ran on a treadmill at three speeds: 12, 14, and 16 km·h-1. Each running speed was performed with both FFS and RFS patterns. Lower limb kinematics in the sagittal plane and normalized elec...
Purpose The multidimensional role of hamstring muscle group strength in athletic performance and ... more Purpose The multidimensional role of hamstring muscle group strength in athletic performance and injury prevention is well documented, and nordic hamstring exercise (NHE) is a popular method for the development of hamstring strength. Our aim was to examine the EMG characteristics of the eccentric NHE as well as the effects of long-term eccentric NHE training on muscle strength and vertical jump performance in 10- to 11-year-old female handball players. Methods Players from the same handball team were randomly assigned to an eccentric NHE training (13 players) or a control group (10 players). Both groups continued their regular handball training routine, but the NHE group performed additional eccentric NHE exercises once or twice a week, with progressively increasing volume, over 20 weeks. To test training effects, countermovement jump (CMJ) height, eccentric hamstring impulse, peak torque, and angle of peak torque were evaluated before, during and after the training period. In the p...
Based on the current literature, the link between Achilles tendon moment arm length and running e... more Based on the current literature, the link between Achilles tendon moment arm length and running economy is not well understood. Therefore, the aim of this study was to further investigate the connection between Achilles tendon moment arm and running economy and the influence of Achilles tendon moment arm on the function of the plantarflexor muscle-tendon unit during running.Ten male competitive marathon runners volunteered for this study. The participants ran on a treadmill at two running speeds: 3 and 3.5 m s−1. During running the oxygen consumption, lower leg kinematics, electrical activity of plantar flexor muscles, and fascicle behavior of the lateral gastrocnemius were measured simultaneously. On the second occasion, an MRI scan of the right leg was taken and used to estimate the Achilles tendon moment arm length.There was a negative correlation between running economy and the body height normalized moment arm length at both selected speeds (r = −0.68, P = 0.014 and r = −0.70, ...
Introduction. In human locomotion every external condition generates a strategy. The aim of this ... more Introduction. In human locomotion every external condition generates a strategy. The aim of this study is to analyze the kinematics parameters and to indentify the changes in movement pattern and muscle activity of race-walkers (RW). Methods. Twelve elite RW have race walking on a treadmill for 5 minutes each slope (0, 2 and 7%) in iso-efficiency speed (IES1) with heart rate and sEMG on leg muscles constantly monitored. Digital cameras (210 Hz) were used to record; Dartfish 5.5Pro was used to perform a 2D video analysis, while for statistical analysis was used Anova. (1) The IES (km/h) for each subject at 0% grade was the average speed during the best performance in the 10000 m race, minus 1 km/h, which corresponds to the ~50% Vo2MAX and requires an energy cost (Cw0) of 5.0 J/m/kg according to previous studies (Di Prampero 1986). Moreover, according to previous data (Minetti et al. 2002) the increase of Cw as a function of ground slope is: 0.15 * slope (%) + Cw0. We calculated for each ground slope the IES at which the Vo2 was equal to the oxygen consumption during level race walking using the following equation: Vo2= (Cw0/21(J/m) * (IES0/0.06 (m/min)) IES= (Vo2 * 21 * 0.06)/(0.15(Cw) * slope (%) + (Cw0)) Results IES, step length (SL) and frequency (SF) decrease as a function of the increasing slope: IES0 12.5 \u2013 IES2 11.8 \u2013 IES7 10.3; SL= (0-2%= -3.71%, n.s.; 0-7%= -12.23%, p&lt;0.001); SF= (0-2%= -2.38%, n.s.; 0-7%= -6.07%, p&lt;0.01). The contact time (CT) and heart rate (HR) increase at the increasing slope: CT= (0-2%= 2.46%, n.s.; 0-7%= 6.56%, p&lt;0.01); HR= (0-2%= 0.62%, n.s.; 0-7%= 3.25%, p&lt;0.05). The sEMG activity was reduced at the increasing slope in: tibialis anterior (0-2%= 22.49%, p&lt;0.0001; 0-7%= 41.18%, p&lt;0.0001); rectus femoris (0-2%= 15.35%, p&lt;0.0001; 0-7%= 29.13%, p&lt;0.0001). While the sEMG activity was increased in this muscles: vastus lateralis (0-2%= 22.95%, p&lt;0.0001; 0-7%= 31.15%, p&lt;0.0001); gastrocnemius medialis (0-2%= 21.40%, p&lt;0.001; 0-7%= 48.37%, p&lt;0.0001); biceps femoris (0-2%= 190.78%, p&lt;0.0001; 0-7%= 201.37%, p&lt;0.0001). Discussion. These results provide the resultant of the real mechanical work in different slopes without increasing energetic cost, validating the equation to calculate the speed in RW only at IES between zero and 2% gradient. While for higher gradient levels the procedure used in this study seems to overestimate the speed, probably due to the different biomechanics between walking (Minetti et al., 2002) and race walking. References Di Prampero PE. The energy cost of human locomotion on land and in water. (1986). Int J Sports Med, 7 (2), 55-72. Minetti AE, Moia C, Roi GS, Susta D, Ferretti G. Energy cost of walking and running at extreme uphill and downhill slopes. (2002). J Appl Physiol, 93(3),1039-1046
Flexor hallucis longus (FHL) muscle has several functions, including plantarflexion of the ankle,... more Flexor hallucis longus (FHL) muscle has several functions, including plantarflexion of the ankle, flexion of the big toe and support of the medial longitudinal arch. To date, only a few studies have used non-invasive methods to examine FHL behavior during real-life movements, although the proper functioning of this muscle may be important to increase sport performance, the altered FHL function may contribute to the susceptibility to Achilles tendinopathy and the function of FHL is altered in other clinical conditions such as flatfoot. FHL seems to be multifunctional but other active and passive structures also contribute to the same functions. Because of the multifunctionality of the foot structures and FHL itself, it is hard to define the main role of FHL during certain kinds of tasks and real-life movements. It is also more difficult to determine how morphological changes in the FHL affect its function. In this review we summarise studies that have examined FHL function focusing particularly on functionally relevant in vivo measurements, and possible effects of FHL anatomical and functional changes. Furthermore we make suggestions regarding studies that are needed in the future to fill the gaps in our knowledge about the role of FHL.peerReviewe
The human ankle joint and plantar flexor muscle–tendon unit play an important role in endurance r... more The human ankle joint and plantar flexor muscle–tendon unit play an important role in endurance running. It has been assumed that muscle and tendon interactions and their biomechanical behaviours depend on their morphological and architectural characteristics. We aimed to study how plantar flexor muscle characteristics influence marathon running performance and to determine whether there is any difference in the role of the soleus and gastrocnemii. The right lower leg of ten male distance runners was scanned with magnetic resonance imagining. The cross-sectional areas of the Achilles tendon, soleus, and lateral and medial gastrocnemius were measured, and the muscle volumes were calculated. Additional ultrasound scanning was used to estimate the fascicle length of each muscle to calculate the physiological cross-sectional area. Correlations were found between marathon running performance and soleus volume (r = 0.55, p = 0.048), soleus cross-sectional area (r = 0.57, p = 0.04), soleus...
Aims The aim of this study was to examine the effects of gender on the relationship between Funct... more Aims The aim of this study was to examine the effects of gender on the relationship between Functional Movement Screen (FMS) and treadmill-based gait parameters. Methods Twenty elite junior athletes (10 women and 10 men) performed the FMS tests and gait analysis at a fixed speed. Between-gender differences were calculated for the relationship between FMS test scores and gait parameters, such as foot rotation, step length, and length of gait line. Results Gender did not affect the relationship between FMS and treadmill-based gait parameters. The nature of correlations between FMS test scores and gait parameters was different in women and men. Furthermore, different FMS test scores predicted different gait parameters in female and male athletes. FMS asymmetry and movement asymmetries measured by treadmill-based gait parameters did not correlate in either gender. Conclusion There were no interactions between FMS, gait parameters, and gender; however, correlation analyses support the id...
Journal of Strength and Conditioning Research, 2016
Matlák, J, Tihanyi, J, and Rácz, L. Relationship between reactive agility and change of direction... more Matlák, J, Tihanyi, J, and Rácz, L. Relationship between reactive agility and change of direction speed in amateur soccer players. J Strength Cond Res 30(6): 1547-1552, 2016-The aim of the study was to assess the relationship between reactive agility and change of direction speed (CODS) among amateur soccer players using running tests with four directional changes. Sixteen amateur soccer players (24.1 ± 3.3 years; 72.4 ± 7.3 kg; 178.7 ± 6 cm) completed CODS and reactive agility tests with four changes of direction using the SpeedCourt™ system (Globalspeed GmbH, Hemsbach, Germany). Countermovement jump (CMJ) height and maximal foot tapping count (completed in 3 seconds) were also measured with the same device. In the reactive agility test, participants had to react to a series of light stimuli projected onto a screen. Total time was shorter in the CODS test than in the reactive agility test (p &lt; 0.001). Nonsignificant correlations were found among variables measured in the CODS, reactive agility, and CMJ tests. Low common variance (r = 0.03-0.18) was found between CODS and reactive agility test variables. The results of this study underscore the importance of cognitive factors in reactive agility performance and suggest that specific methods may be required for training and testing reactive agility and CODS.
The Journal of sports medicine and physical fitness, 2001
Although the plyometric training has proved its efficiency, it remains generally unknown whether ... more Although the plyometric training has proved its efficiency, it remains generally unknown whether a limited amount of plyometric training could improve movements in subjects who already demonstrate high level of performance. Three different training regimens were performed in order to study effects of plyometric training on elite junior basketball players. While control group (CG) participated only in the regular midseason training activity, another two groups performed a limited amount of plyometric training employing drop jumps from the height of either 50 cm (EG-50) or 100 cm (EG-100). The height of the maximal vertical jump (CMJ), as well as the maximal voluntary force (F) and the rate of force development (RFD) of hip and knee extensors were tested prior to and after the training. An increase in CMJ (4.8 and 5.6 cm in EG-50 and EG-100, respectively), as well as in F of hip extensors and RFD of knee extensors was observed in both experimental groups, while no significant changes ...
Journal of Strength and Conditioning Research, 2014
We examined the susceptibility of fast and slow twitch muscle fibers in the quadriceps muscle to ... more We examined the susceptibility of fast and slow twitch muscle fibers in the quadriceps muscle to eccentric exercise-induced muscle damage. Nine healthy men (age: 22.5 ± 1.6 years) performed maximal eccentric quadriceps contractions at 120°·s-1 over a 120° of knee joint range of motion for 6 consecutive days. Biopsies were taken from the vastus lateralis muscle before repeated bouts of eccentric exercise on the third and seventh day. Immunohistochemical procedures were used to determine fiber composition and fibronectin activity. Creatine kinase (CK) and lactate dehydrogenase (LDH) were determined in serum. Average torque was calculated in each day for each subject. Relative to baseline, average torque decreased 37.4% till day 3 and increased 43.0% from the day 3 to day 6 (p &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.001). Creatine kinase and LDH were 70.6 and 1.5 times higher on day 3 and 75.5 and 1.4 times higher on day 6. Fibronectin was found in fast fibers in subjects with high CK level on day 3 and 7 after exercise, but on day 7, fibronectin seemed in both slow and fast fibers except in muscles of 2 subjects with high fast fiber percentage. Peak torque and muscle fiber-type composition measured at baseline showed a strong positive association on day 3 (r = 0.76, p &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.02) and strong negative association during recovery between day 3 and day 6 (r = -0.76, p &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.02), and day 1 and day 6 (r = 0.84, p &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.001). We conclude that the damage of fast fibers preceded the damage of slow fibers, and muscles with slow fiber dominance were more susceptible to repeated bouts of eccentric exercise than fast fiber dominance muscles. The data suggest that the responses to repeated bouts of eccentric exercise are fiber-type-dependent in the quadriceps muscle, which can be the basis for the design of individualized strength training protocols.
Journal of Strength and Conditioning Research, 2013
To determine the acute task and stretch-load dependency of neuromuscular impairments after muscle... more To determine the acute task and stretch-load dependency of neuromuscular impairments after muscle-damaging exercises, we examined the magnitude of strength deficits in isometric and stretch-shortening cycle (SSC) contractions after a single bout of exercise. Ten trained men performed 90 unilateral isokinetic eccentric-concentric knee extensions on a dynamometer. Plasma creatine kinase activity, muscle soreness, maximal isometric torque, short-range stiffness, and peak torque in the eccentric phase of the SSC contraction at 3 stretch-loads (120, 150, and 180 J) were determined in the quadriceps before and 24 hours after exercise. During SSC, positive mechanical work and efficiency were also calculated. Creatine kinase and soreness increased at 24 hours (p &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.05). In each of the 3 stretch-load conditions, muscle damage affected short-range stiffness less than isometric and peak SSC torque (p &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.05), providing evidence for a selective impairment in contractile function after muscle damage. With greater SSC stretch-load peak, SSC torque deficit increased linearly, whereas short-range stiffness deficit was unaffected. Efficiency declined only at the 180-J condition (p &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.05) as a result of decreased positive work (p &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.05). It was concluded that intense exercise produced microtrauma in the muscle, and a selective loss of force generating capacity, which suggests greater damage to the contractile machinery. Practitioners may expect greater acute impairment of force generation in movements that use large loads in their daily training drills. However, altered knee flexion strategy during SSC may compensate for the force deficit, preserving mechanical efficiency at smaller stretch-loads.
Leg extensor muscle characteristics, running speed and serum testosterone were studied in sixteen... more Leg extensor muscle characteristics, running speed and serum testosterone were studied in sixteen males and twelve female sprinters. The rise of center of gravity was measured during squat jumps executed without (SJ) and with extra loads (SJbm), counter movement jump (CMJ) and continuous jumping (CJ) for 5 s. Nine females and nine males performed also half-squat exercises with extra loads ranging from 50% to 200% of the subject's body mass (bm). Average mechanical power (P), force (F) and velocity (v) were calculated and measured during half-squat exercises using the Ergopower®. Total serum testosterone (TT) was determined in venous blood. In women, 60 m dash, SJ, CMJ and CJ performances were significantly lower (P<0.001) than men. Gender differences were not found in F during half-squat exercises and in SJbm. Women demonstrated significantly higher ratios CMJ:SJ and CJ:SJ than men. With loads 50-100 % of bm men demonstrated greater v and P than women. It was suggested that high testosterone level in men might be a factor ensured superiority in explosive power and speed, but not in muscle strength adjusted to body mass.
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