Aim The concept of post-activation potentiation(PAP)is still novel from a training perspective and lacks breadth relative to weightlifting exercises.Purpose The purpose of this study was to investigate the acute effec...Aim The concept of post-activation potentiation(PAP)is still novel from a training perspective and lacks breadth relative to weightlifting exercises.Purpose The purpose of this study was to investigate the acute effects of a conditioning activity(clean high pulls)on the performance of a main activity(clean)after the conditioning activity.Methods Eleven volunteers who engaged in weightlifting(Male=5,Female=6)participated in two different testing ses-sions(experimental vs.control).Baseline measurements were taken following the warm-up.The testing condition was performed and additional measurements were taken at 30 s,2 min,4 min,6 min,8 min,10 min,and 12 min into recovery.A linear position transducer was used to collect peak power,peak velocity,and displacement of the barbell during the clean.Multiple 2×8 repeated measures ANOVAs were used to analyze the data along with a paired samples t test between baseline and"best"values.Results There was no interaction or main effect for condition(P>0.05).However,there was a significant main effect for time(P<0.05)for all variables.The"best"values were significantly(P<0.05)greater than baseline values(peak power:experimental=1354.76 ±521.24 W vs.baseline 1216.03 ±492.30 W;peak velocity:experimental=2.66 ±0.44 m/s vs.baseline 2.50 ±0.44 m/s;displacement:experimental=111.07 ± 12.09 cm vs.baseline 107.01 ± 11.32 cm).Conclusions The findings of this study are in partial agreement with previous literature where the warm-up was probably enough to elicit PAP.Therefore,recommendations for future studies could include utilizing a more elite population and to ensure all potential participants can squat at least 2 x their body weight.展开更多
On the slices of sensorimotor and frontal cortex in layer V of guinea pigs the diversity of neuronal spontaneous activity, the mechanism of its origin and functional specificity were studied. In both regions, neurons ...On the slices of sensorimotor and frontal cortex in layer V of guinea pigs the diversity of neuronal spontaneous activity, the mechanism of its origin and functional specificity were studied. In both regions, neurons that did not have spontaneous activity predominated (39% in the sensorimotor cortex and 32% in the frontal cortex) over neurons with any other firing levels. The iontophoretic application of the excitatory transmitter, glutamate, caused activation spike reactions in all registered neurons;moreover, short-term activation reactions to glutamate had a significantly longer after-discharge in neurons of the frontal cortex (up to 2500 ms and more) compared to reactions of neurons of the sensorimotor region. This means that postexcitatory hyperpolarization in nerve cells of the frontal cortex is less expressed and, therefore, they have a lower density of K+ channels on their membranes. With an increase in the level of spontaneous activity, K+ membrane permeability decreases, which is confirmed by the appearance of a long activation reaction to acetylcholine (which blocks K+ channels), exactly when spontaneous firing appears in “silent” neurons. Despite the fact that spontaneous activity is formed by glutamatergic excitation, its considerable diversity is associated with the structural and membrane characteristics of neurons, which determine the different degrees of EPSPs attenuation on the way of moving along dendrites. Acetylcholine regulates this process in different ways, in accordance with different states of K+ membrane permeability. Therefore, the lower content of K+ channels on the membranes of neurons of the frontal cortex does not allow regulating spontaneous activity in the same range as occurs in neurons of the sensorimotor region. The presence of a high proportion of spontaneously inactive neurons in the cortex (higher in the sensorimotor cortex) suggests that cortical neurons are generally characterized by a high density of K+ channels and a significant increase in firing response to acetylcholine, while spontaneously active neurons cannot control the spontaneous activity in a wide range.展开更多
文摘Aim The concept of post-activation potentiation(PAP)is still novel from a training perspective and lacks breadth relative to weightlifting exercises.Purpose The purpose of this study was to investigate the acute effects of a conditioning activity(clean high pulls)on the performance of a main activity(clean)after the conditioning activity.Methods Eleven volunteers who engaged in weightlifting(Male=5,Female=6)participated in two different testing ses-sions(experimental vs.control).Baseline measurements were taken following the warm-up.The testing condition was performed and additional measurements were taken at 30 s,2 min,4 min,6 min,8 min,10 min,and 12 min into recovery.A linear position transducer was used to collect peak power,peak velocity,and displacement of the barbell during the clean.Multiple 2×8 repeated measures ANOVAs were used to analyze the data along with a paired samples t test between baseline and"best"values.Results There was no interaction or main effect for condition(P>0.05).However,there was a significant main effect for time(P<0.05)for all variables.The"best"values were significantly(P<0.05)greater than baseline values(peak power:experimental=1354.76 ±521.24 W vs.baseline 1216.03 ±492.30 W;peak velocity:experimental=2.66 ±0.44 m/s vs.baseline 2.50 ±0.44 m/s;displacement:experimental=111.07 ± 12.09 cm vs.baseline 107.01 ± 11.32 cm).Conclusions The findings of this study are in partial agreement with previous literature where the warm-up was probably enough to elicit PAP.Therefore,recommendations for future studies could include utilizing a more elite population and to ensure all potential participants can squat at least 2 x their body weight.
文摘On the slices of sensorimotor and frontal cortex in layer V of guinea pigs the diversity of neuronal spontaneous activity, the mechanism of its origin and functional specificity were studied. In both regions, neurons that did not have spontaneous activity predominated (39% in the sensorimotor cortex and 32% in the frontal cortex) over neurons with any other firing levels. The iontophoretic application of the excitatory transmitter, glutamate, caused activation spike reactions in all registered neurons;moreover, short-term activation reactions to glutamate had a significantly longer after-discharge in neurons of the frontal cortex (up to 2500 ms and more) compared to reactions of neurons of the sensorimotor region. This means that postexcitatory hyperpolarization in nerve cells of the frontal cortex is less expressed and, therefore, they have a lower density of K+ channels on their membranes. With an increase in the level of spontaneous activity, K+ membrane permeability decreases, which is confirmed by the appearance of a long activation reaction to acetylcholine (which blocks K+ channels), exactly when spontaneous firing appears in “silent” neurons. Despite the fact that spontaneous activity is formed by glutamatergic excitation, its considerable diversity is associated with the structural and membrane characteristics of neurons, which determine the different degrees of EPSPs attenuation on the way of moving along dendrites. Acetylcholine regulates this process in different ways, in accordance with different states of K+ membrane permeability. Therefore, the lower content of K+ channels on the membranes of neurons of the frontal cortex does not allow regulating spontaneous activity in the same range as occurs in neurons of the sensorimotor region. The presence of a high proportion of spontaneously inactive neurons in the cortex (higher in the sensorimotor cortex) suggests that cortical neurons are generally characterized by a high density of K+ channels and a significant increase in firing response to acetylcholine, while spontaneously active neurons cannot control the spontaneous activity in a wide range.
