The pattern of stimulation influences the amount of oscillatory work done by frog muscle (original) (raw)
Related papers
Journal of Muscle Research and Cell Motility, 1988
Work per cycle was calculated in isolated frog sartorius muscle by measuring force as the activated muscle was subjected to sinusoidal length changes. Work per cycle was calculated from the area of the loop formed when force was plotted against length. Measurements were made at 20 ~ C using physiological solutions with high plie (7.9) or low plie (6.6). Net work done per cycle was positive when the muscle was activated during the shortening phase of the length cycle. Maximum work done increased as excursion amplitude increased and was about 17J kg -I at a strain of 12% (i.e. Lo + 6%) at a cycle frequency of 2 Hz. Maximum power was 35 W kg -1 and was about 25% less at the lower plie. Power measured in this way is much less than the value calculated from force-velocity curves. However, power calculated from force-velocity curves neglects the time that the muscle must be inactive during locomotion. Thus the measurements of the present study are realistic relative to actual mechanical power output during locomotion.
Canadian Journal of Zoology-revue Canadienne De Zoologie, 1993
LUIKER, E. A., and STEVENS, E.D. 1993. Effect of stimulus train duration and cycle frequency on the capacity to do work in the pectoral fin muscle of the pumpkinseed sunfish, Lepomis gibbosus. Can. J. Zool. 71: 2 185 -2 189. The goal of our experiment was to elucidate the effect of stimulus duty cycle (the percentage of the cycle that the muscle was stimulated), phase (the relative timing of the imposed sinusoidal length change and stimulation), and muscle cycle frequency (the speed at which the muscle was cycled) on work and power in the pectoral fin muscle of a labriform swimmer, the pumpkinseed sunfish, Lepomis gibbosus. Stimulus train duration was varied from a twitch to a 40% duty cycle; cycle frequency was varied from 1 to 8 Hz. Work was calculated as the area of work loops produced by muscle contractions while the muscle was undergoing sinusoidal length changes. Maximum net work per cycle (6.2 Jlkg) was produced at 1 Hz cycle frequency and a 32% duty cycle. Maximum power (26.7 Wlkg) was produced at 5 Hz cycle frequency and a 16% duty cycle. As cycle frequency increased, the duty cycle and the stimulus train duration that produced maximum work decreased. The relatively long relaxation time compared with the length of time required to complete the whole cycle precluded the muscle from doing net positive work at high cycle frequencies.
The frequency response of frog muscle spindles under various conditions
The Journal of Physiology
1. Nerve impulses were recorded from afferents from non-contracting spindles from the isolated extensor longus dig. IV muscle of the frog during small sinusoidal changes in muscle length at frequencies from 0.001 to 100 Hz. A computer of average transients was used to average the spike distribution during a number of cycles, and hence to determine the spindle response in impulses/sec at different phases of the cycle.2. At any one frequency the response could be described by a sinusoid, whose amplitude was approximately proportional to the amplitude of the stretch and whose phase was approximately constant, together with a non-linearity dependent principally upon non-linearities in the static response.3. The frequency response was estimated from the sinusoid responses. In conventional terms, it consisted of a straight line of positive slope below 2 Hz and a maximum between 7 and 16 Hz.4. The slope of the frequency response was dependent on the mean length of the preparation, typicall...
2001
Muscle contractions are extremely dynamic, for being the net result of complex physiological processes regulated by different time constants. Mechanisms leading to either enhancement (potentiation) or decrease (fatigue) in muscle force coexist (Huijing, 1998; Rassier et al., 2000). Furthermore, such mechanisms may have different relative importance at different muscle lengths (Huijing et al., 1996). Even during short sustained contractions, the shape of muscle force-time trace in response to the same stimulus varies with the length of the muscle at which the stimulus is applied. The shape of the response of a muscle stimulated at any isometric length depends on the frequency of the applied pulse train. The main objective of this study was to investigate and model the dynamics of sustained isometric contractions over a range of muscle lengths at submaximal frequencies, with as few parameters as possible. Accurate descriptions of important intrinsic muscle properties over the range of...
Frequency-Dependent Reaction of the Triceps Surae Muscle of the Mouse During Electromyostimulation
Frontiers in Physiology
The difference in the efficacy of altered stimulation parameters in whole-bodyelectromyostimulation training (WB-EMS) has hardly been examined. Higher impulse frequencies (>50 Hz) might be most adequate for strength gains because of the force frequency relationship (FFR), which describes a greater force production by increasing the applied frequency. Frequencies below this value, however, also seem to have positive influences on muscle strength increases. Therefore, the aim of this study was to analyze possible muscle length changes to different stimulation frequencies of the dissected mouse triceps surae muscle. A bending rod transducer was used to measure and compare changes in muscle lengths at different frequencies in relation to the initial length in the prepared muscle. We found significant differences between the muscle shortening at different frequencies (p < 0.001). At 20 Hz the largest muscle shortening was observed (20 Hz = 3.32 ± 2.06, 60 Hz = 0.77 ± 0.58, 85 Hz = 0.32 ± 0.29, 100 Hz = 0.31 ± 0.29). From a frequency of 60 Hz, the muscle shortening decreased progressively, at stimulation frequencies above 60 Hz the lowest shortenings were recorded. The results demonstrate a different behavior of the isolated triceps surae muscle of the mouse in an ex vivo environment. Even if there is no FFR in this investigation, the results indicate a higher metabolic demand using higher frequencies in electromyostimulation, despite the experimental execution in ex vivo design. Therefore, future studies should take this faster fatigue into account when drawing up training protocols in order to counteract possible frequency modulations.
The optimal stimulation pattern for skeletal muscle is dependent on muscle length
IEEE Transactions on Neural Systems and Rehabilitation Engineering, 2002
Stimulation patterns can be optimized by maximizing the force-time integral (FTI) per stimulation pulse of the elicited muscle contraction. Such patterns, providing the desired force output with the minimum number of pulses, may reduce muscle fatigue, which has been shown to correlate to the number of pulses delivered. Applications of electrical stimulation to use muscle as a controllable biological actuator may, therefore, be improved. Although muscle operates over a range of lengths, optimized patterns have been determined only at optimal muscle length. In this study, the patterns with up to four pulses that produced the highest isometric FTI were determined at 10 muscle lengths for 11 rabbit tibialis anterior muscles. The interpulse intervals (IPIs) used ranged from 4 to 54 ms. At high muscle length, the optimal stimulation pattern consisted of an initial short IPI (doublet) followed by longer IPIs, in agreement with previous studies. However, at low length, the third pulse still elicited more than linear summation (triplet); furthermore, the relative enhancement of the FTI per pulse was considerably larger at low length than at high length, suggesting that optimal stimulation patterns are length dependent.
Energetics of activation in frog and toad muscle
The Journal of physiology, 1972
1. If activation heat reflects the operation of the calcium pump it should be independent of actomyosin activity. The semitendinosus preparation affords a technique for removing actomyosin activity since the muscle can be stretched till there is almost no overlap between the filaments.2. Heat production, H, in twitches and tetani of stretched muscle fits the relation H = A+M.P/P(ot) where P/P(ot) is the fraction of the optimal tension remaining at the stretched length and A and M are assumed to be the activation dependent and actomyosin dependent heat components.3. For twitches the A component is early and fast and constitutes 0.26 (S.D. 0.09) of the heat production at normal muscle lengths. Its time course is similar in both frog and toad muscle although both M and P are twofold slower in toad muscle. High concentrations of CO(2) slow only M and P(ot). The A component is associated with a normal recovery heat.4. The twitch-tetanus tension ratio, after correction for the extra short...