scholarly journals Prolonged low-frequency force depression is underestimated when assessed with doublets compared with tetani in the dorsiflexors

2019 ◽  
Vol 126 (5) ◽  
pp. 1352-1359 ◽  
Author(s):  
Luca Ruggiero ◽  
Christina D. Bruce ◽  
Paul D. Cotton ◽  
Gabriel U. Dix ◽  
Chris J. McNeil
Keyword(s):  
Eccentric Exercise ◽  
Gold Standard ◽  
Low Frequency ◽  
Valid Measure ◽  
Tetanic Force ◽  
Paired Stimuli ◽  
Force Depression ◽  
Before And After ◽  
Supramaximal Stimulation ◽  
Voluntary Contractions

Prolonged low-frequency force depression (PLFFD) after damaging eccentric exercise may last for several days. Historically, PLFFD has been calculated from the tetanic force responses to trains of supramaximal stimuli. More recently, for methodological reasons, stimulation has been reduced to two pulses. However, it is unknown whether doublet responses provide a valid measure of PLFFD in the days after eccentric exercise. In 12 participants, doublets and tetani were elicited at 10 and 100 Hz before and after (2, 3, 5 min, 48 and 96 h) 200 eccentric maximal voluntary contractions of the dorsiflexors. Doublet and tetanic torque responses at 10 Hz were similarly depressed throughout recovery ( P > 0.05; e.g., 2 min: 58.9 ± 12.8% vs. 57.1 ± 14.5% baseline; 96 h: 85.6 ± 11.04% vs. 85.1 ± 10.8% baseline). At 100 Hz, doublet torque was impaired more than tetanic torque at all time points ( P < 0.05; e.g., 2 min: 70.5 ± 14.2% vs. 88.1 ± 11.7% baseline; 96 h: 83.0 ± 14.2% vs. 98.7 ± 9.5% baseline). As a result, the postfatigue reduction of the 10 Hz-to-100 Hz ratio (PLFFD) was markedly greater for tetani than for doublets ( P < 0.05; e.g., 2 min: 64.3 ± 15.1% vs. 83.0 ± 5.8% baseline). In addition, the doublet ratio recovered by 48 h (99.2 ± 5.0% baseline), whereas the tetanic ratio was still impaired at 96 h (88.2 ± 9.7% baseline). Our results indicate that doublets are not a valid measure of PLFFD in the minutes and days after eccentric exercise. If study design favors the use of paired stimuli, it should be acknowledged that the true magnitude and duration of PLFFD are likely underestimated.NEW & NOTEWORTHY Prolonged low-frequency force depression (PLFFD) will result from damaging exercise and may last for several days. After 200 eccentric maximal dorsiflexor contractions, we compared the gold-standard measure of PLFFD (calculated using trains of supramaximal stimulation) to the value obtained from an alternative technique that is becoming increasingly common (paired supramaximal stimuli). Doublets underestimated the magnitude and duration of PLFFD compared with tetani, so caution must be used when reporting PLFFD derived from paired stimuli.

Maximal results with minimal stimuli: the fewest high-frequency pulses needed to measure or model prolonged low-frequency force depression in the dorsiflexors

2021 ◽  
Author(s):  
Luca Ruggiero ◽  
Christina D. Bruce ◽  
Hannah B. Streight ◽  
Chris J. McNeil
Keyword(s):  
Gold Standard ◽  
High Frequency ◽  
Low Frequency ◽  
Pulse Number ◽  
Limits Of Agreement ◽  
Force Depression ◽  
Before And After ◽  
Minimum Number ◽  
Experimental Values ◽  
Further Development

Quantifying prolonged low-frequency force depression (PLFFD) with the gold-standard 1-s trains presents challenges so paired-pulses have been used. Owing to greater impairment of high-frequency doublet than tetanic torque, paired-pulses underestimate PLFFD. This study aimed to approximate the minimum number of high-frequency pulses needed to avoid such underestimation and assess the feasibility of modelling PLFFD from a limited number of experimental pulses. In 13 participants, a 1-s 10-Hz train and 100-Hz trains with 2, 4, 7, 12, 15, 25, 50, or 100 pulses were evoked before and after (15 min, 2, 4, and 7 d) eccentric exercise of the dorsiflexors. With ≤ 12 pulses, impairment of 100-Hz torque was greater than the 1-s train (P ≤ 0.05; e.g., 12 vs. 100 pulses at 4d: 97.8 ± 8.5% vs. 100.5 ± 8.2% baseline). Consequently, with ≤ 12 pulses, PLFFD was underestimated compared to the gold-standard measure (P ≤ 0.05; e.g., 12 vs. 100 pulse 10:100 Hz torque ratio at 4d: 86.8 ± 12.8% vs. 84.6 ± 13.5% baseline). Modelling reproduced 10:100 Hz ratios (PLFFD) with 95% limits of agreement of −13.6-16.7% of experimental values with ≥ 12 pulses. Our results indicate that a minimum of 13-25 100-Hz pulses are needed to accurately quantify PLFFD in the dorsiflexors. Although this may not be the minimum range for other muscles, a similar relationship with pulse number likely exists. Modelling may eventually provide an option to estimate PLFFD from experimental trains with relatively few pulses; however, further development is imperative to reduce variability.

Females and males do not differ for fatigability, muscle damage and magnitude of the repeated bout effect following maximal eccentric contractions

2020 ◽  
Author(s):  
Christina D. Bruce ◽  
Luca Ruggiero ◽  
Gabriel U. Dix ◽  
Paul D. Cotton ◽  
Chris J McNeil
Keyword(s):  
Muscle Fatigue ◽  
Muscle Damage ◽  
Low Frequency ◽  
Calcium Handling ◽  
High Frequency Stimulation ◽  
Repeated Bout Effect ◽  
Indirect Measure ◽  
Force Depression ◽  
Before And After ◽  
Repeated Bout

Unaccustomed eccentric (ECC) exercise induces muscle fatigue as well as damage and initiates a protective response to minimize impairments from a subsequent bout (i.e., repeated bout effect; RBE). It is uncertain if the sexes differ for neuromuscular responses to ECC exercise and the ensuing RBE. Twenty-six young adults (13 females) performed two bouts (four weeks apart) of 200 ECC maximal voluntary contractions (MVCs) of the dorsiflexors. Isometric (ISO) MVC torque and the ratio of ISO torque in response to low- vs. high-frequency stimulation (10:100Hz) were compared before and after (2-10min and 2, 4, and 7d) exercise. The decline in ECC and ISO MVC torque, and the 10:100Hz ratio following bout one did not differ between sexes (P > 0.05), with reductions from baseline of 31.5 ± 12.3, 24.1 ± 15.4, and 51.3 ± 12.2%, respectively. After bout two, the 10:100Hz ratio declined less (45.0 ± 12.4% from baseline) and ISO MVC torque recovered sooner compared to bout one but no differences between sexes were evident for the magnitude of the RBE (P > 0.05). These data suggest that fatigability with ECC exercise does not differ for the sexes and adaptations that mitigate impairments to calcium handling are independent of sex. NOVELTY BULLETS: • One bout of 200 maximal eccentric dorsiflexor contractions caused equivalent muscle fatigue and damage for females and males • The repeated bout effect observed after a second bout four weeks later also had no sex-related differences • Prolonged low-frequency force depression is promoted as an indirect measure of muscle damage in humans

Low-frequency depression of tension in the cat gastrocnemius muscle after eccentric exercise

2004 ◽  
Vol 97 (4) ◽  
pp. 1195-1202 ◽  
Author(s):  
S. Parikh ◽  
D. L. Morgan ◽  
J. E. Gregory ◽  
U. Proske
Keyword(s):  
Eccentric Exercise ◽  
Muscle Activation ◽  
Low Frequency ◽  
Muscle Length ◽  
Isometric Tension ◽  
Medial Gastrocnemius ◽  
Eccentric Contractions ◽  
Optimum Length ◽  
Length Dependence ◽  
Before And After

Subjecting a muscle to a series of eccentric contractions in which the contracting muscle is lengthened results in a number of changes in its mechanical properties. These include a fall in isometric tension that is particularly pronounced during low-frequency stimulation, a phenomenon known as low-frequency depression (LFD). Reports of LFD have not taken into account the shift in optimum length for active tension generation to longer muscle lengths that takes place after eccentric contractions. Given the length dependence of the stimulation frequency-tension curve, we tested the hypothesis that the change in this relationship after eccentric exercise is due to the shift in optimum length. We measured LFD by recording tension in response to a linearly increasing rate of stimulation of the nerve to medial gastrocnemius of anesthetized cats, over the range 0–100 pulses per second. Tension responses were measured before and after 50 eccentric contractions consisting of 6-mm stretches starting at 3 mm below optimum length and finishing at 3 mm above it. An index of LFD was derived from the tension responses to ramp stimulation. It was found that LFD after the eccentric contractions was partly, but not entirely, due to changes in the muscle's optimum length. An additional factor was the effect of fatigue. These observations led to the conclusion that the muscle length dependence of LFD was reduced by eccentric contractions. All of this means that after eccentric exercise the tension deficit at low rates of muscle activation is likely to be less severe than first thought.

Postcontractile force depression in humans is associated with an impairment in SR Ca2+ pump function

2000 ◽  
Vol 278 (1) ◽  
pp. R87-R94 ◽  
Author(s):  
R. Tupling ◽  
H. Green ◽  
S. Grant ◽  
M. Burnett ◽  
D. Ranney
Keyword(s):  
Atpase Activity ◽  
Mechanical Performance ◽  
Vastus Lateralis ◽  
Recovery Period ◽  
Isometric Exercise ◽  
Low Frequency ◽  
Voluntary Contraction ◽  
Free Calcium ◽  
Force Depression ◽  
Before And After

To investigate the hypothesis that intrinsic changes in sarcoplasmic reticulum (SR) Ca2+-sequestration function can be implicated in postcontractile depression (PCD) of force in humans, muscle tissue was obtained from the vastus lateralis and determinations of maximal Ca2+ uptake and maximal Ca2+-ATPase activity were made on homogenates obtained before and after the induction of PCD. Eight untrained females, age 20.6 ± 0.75 yr (mean ± SE), performed a protocol consisting of 30 min of isometric exercise at 60% maximal voluntary contraction and at 50% duty cycle (5-s contraction and 5-s relaxation) to induce PCD. Muscle mechanical performance determined by evoked activation was measured before (0 min), during (15 and 30 min), and after (60 min) exercise. The fatiguing protocol resulted in a progressive reduction ( P < 0.05) in evoked force, which by 30 min amounted to 52% for low frequency (10 Hz) and 20% for high frequency (100 Hz). No force restoration occurred at either 10 or 100 Hz during a 60-min recovery period. Maximal SR Ca2+-ATPase activity (nmol ⋅ mg protein− 1 ⋅ min− 1) and maximal SR Ca2+ uptake (nmol ⋅ mg protein− 1 ⋅ min− 1) were depressed ( P < 0.05) by 15 min of exercise [192 ± 45 vs. 114 ± 8.7 and 310 ± 59 vs. 205 ± 47, respectively; mean ± SE] and remained depressed at 30 min of exercise. No recovery in either measure was observed during the 60-min recovery period. The coupling ratio between Ca2+-ATPase and Ca2+ uptake was preserved throughout exercise and during recovery. These results illustrate that during PCD, Ca2+uptake is depressed and that the reduction in Ca2+ uptake is due to intrinsic alterations in the Ca2+ pump. The role of altered Ca2+ sequestration in Ca2 release, cytosolic-free calcium, and PCD remains to be determined.

Effects of activation frequency and force on low-frequency fatigue in human skeletal muscle

1999 ◽  
Vol 86 (4) ◽  
pp. 1337-1346 ◽  
Author(s):  
Stuart A. Binder-Macleod ◽  
David W. Russ
Keyword(s):  
Healthy Subjects ◽  
Human Skeletal Muscle ◽  
Low Frequency ◽  
Variable Frequency ◽  
Activation Pattern ◽  
Constant Frequency ◽  
Mean Frequency ◽  
Before And After ◽  
Low Frequency Fatigue ◽  
Force Time

No comparison of the amount of low-frequency fatigue (LFF) produced by different activation frequencies exists, although frequencies ranging from 10 to 100 Hz have been used to induce LFF. The quadriceps femoris of 11 healthy subjects were tested in 5 separate sessions. In each session, the force-generating ability of the muscle was tested before and after fatigue and at 2, ∼13, and ∼38 min of recovery. Brief (6-pulse), constant-frequency trains of 9.1, 14.3, 33.3, and 100 Hz and a 6-pulse, variable-frequency train with a mean frequency of 14.3 Hz were delivered at 1 train/s to induce fatigue. Immediately postfatigue, there was a significant effect of fatiguing protocol frequency. Muscles exhibited greater LFF after stimulation with the 9.1-, 14.3-, and variable-frequency trains. These three trains also produced the greatest mean force-time integrals during the fatigue test. At 2, ∼13, and ∼38 min of recovery, however, the LFF produced was independent of the fatiguing protocol frequency. The findings are consistent with theories suggesting two independent mechanisms behind LFF and may help identify the optimal activation pattern when functional electrical stimulation is used.

Effect of High Dose Vitamin C Supplementation on Muscle Soreness, Damage, Function, and Oxidative Stress to Eccentric Exercise

2006 ◽  
Vol 16 (3) ◽  
pp. 270-280 ◽  
Author(s):  
S.C. Bryer ◽  
A.H. Goldfarb
Keyword(s):  
Oxidative Stress ◽  
Vitamin C ◽  
Eccentric Exercise ◽  
Muscle Function ◽  
Muscle Soreness ◽  
Damage Function ◽  
High Dose ◽  
Before And After ◽  
Vitamin C Supplementation ◽  
Glutathione Oxidation

This study investigated if vitamin C supplementation before and after eccentric exercise could reduce muscle soreness (MS), oxidative stress, and muscle function. Eighteen healthy men randomly assigned to either a placebo (P) or vitamin C (VC) (3 g/d) treatment group took pills for 2 wk prior and 4 d after performing 70 eccentric elbow extensions with their non-dominant arm. MS increased in both groups with significantly reduced MS for the first 24 h with VC. Range of motion was reduced equally in both groups after the exercise (P ≥ 0.05). Muscle force declined equally and was unaffected by treatment. VC attenuated the creatine kinase (CK) increase at 48 h after exercise with similar CK after this time. Gluta-thione ratio (oxidized glutathione/total glutathione) was significantly increased at 4 and 24 h with P but VC prevented this change. These data suggest that vitamin C pretreatment can reduce MS, delay CK increase, and prevent blood glutathione oxidation with little influence on muscle function loss.

Effect of Incisions in the Brainstem Commissural Network on the Short-Term Vestibulo-Ocular Adaptation of the CAT

1991 ◽  
Vol 1 (3) ◽  
pp. 223-239
Author(s):  
G. Cheron
Keyword(s):  
Low Frequency ◽  
Adaptive Plasticity ◽  
Training Procedure ◽  
Optokinetic Response ◽  
Mean Values ◽  
Ocular Reflex ◽  
Optokinetic Reflex ◽  
Before And After ◽  
Vestibulo Ocular Reflex ◽  
Vor Adaptation

This study was intended to test the adaptive plasticity of the vestibulo-ocular reflex before and after either a midsagittal or parasagittal incision in the brainstem. Eye movements were measured with the electromagnetic search coil technique during the vestibulo-ocular reflex (VORD) in the dark, the optokinetic reflex (OKN), and the visuo-vestibular adaptive training procedure. Two types of visual-vestibular combined stimulation were applied by means of low frequency stimuli (0.05 to 0.10 Hz). In order to increase or decrease the VORD gain, the optokinetic drum was oscillated either 180∘ out-of-phase or in-phase with the vestibular stimulus turntable. This “training” procedure was applied for 4 hours. Initial measurements of the VORD were normal with a mean gain value of 0.92 ± 0.08. After 4 hours of “training” with the out-of-phase condition (180∘), VORD gain reached mean values of 1.33 ± 0.11 (n = 6 cats). In the in-phase combination, the mean VORD gain decreased from 1.0 to 0.63 ± 0.02 (n = 2 cats). No significant change of VORD phase was found in any of the cats. Midsagittal or parasagittal pontomedullary brainstem incisions were performed in 4 cats. Recovery of the VOR was tested on the 2nd, 7th, and 30th day after operation. After the 30th day, recovery of the VORD gain stabilized at about 66% of the initial preoperative value. At this stage of the recovery, the optokinetic response (OKN) of the midsagittal-Iesioned cats was practically normal: in the parasagittal-Jesioned cats, the postoperative OKN responses were asymmetric. After stabilization of recovery, lesioned cats were trained with the same adaptation procedure. Although the direct effect of the visuo-vestibular combined stimulation during the training was still operative in all lesioned cats, the adaptive plasticity was completely abolished by the lesions. These results suggest that the commissural brainstem network may play a crucial role in the acquisition of the forced VOR adaptation.

Comparative study on effect of neutral spinal bath and neutral spinal spray on blood pressure, heart rate and heart rate variability in healthy volunteers

2018 ◽  
Vol 16 (2) ◽  
Author(s):  
Arundhati Goley ◽  
A. Mooventhan ◽  
NK. Manjunath
Keyword(s):  
Blood Pressure ◽  
Heart Rate ◽  
Heart Rate Variability ◽  
Healthy Volunteers ◽  
Group Analysis ◽  
Low Frequency ◽  
Single Session ◽  
Arterial Blood ◽  
Before And After ◽  
Instantaneous Heart Rate

Abstract Background Hydrotherapeutic applications to the head and spine have shown to improve cardiovascular and autonomic functions. There is lack of study reporting the effect of either neutral spinal bath (NSB) or neutral spinal spray (NSS). Hence, the present study was conducted to evaluate and compare the effects of both NSB and NSS in healthy volunteers. Methods Thirty healthy subjects were recruited and randomized into either neutral spinal bath group (NSBG) or neutral spinal spray group (NSSG). A single session of NSB, NSS was given for 15 min to the NSBG and NSSG, respectively. Assessments were taken before and after the interventions. Results Results of this study showed a significant reduction in low-frequency (LF) to high-frequency (HF) (LF/HF) ratio of heart rate variability (HRV) spectrum in NSBG compared with NSSG (p=0.026). Within-group analysis of both NSBG and NSSG showed a significant increase in the mean of the intervals between adjacent QRS complexes or the instantaneous heart rate (HR) (RRI) (p=0.002; p=0.009, respectively), along with a significant reduction in HR (p=0.002; p=0.004, respectively). But, a significant reduction in systolic blood pressure (SBP) (p=0.037) and pulse pressure (PP) (p=0.017) was observed in NSSG, while a significant reduction in diastolic blood pressure (DBP) (p=0.008), mean arterial blood pressure (MAP) (p=0.008) and LF/HF ratio (p=0.041) was observed in NSBG. Conclusion Results of the study suggest that 15 min of both NSB and NSS might be effective in reducing HR and improving HRV. However, NSS is particularly effective in reducing SBP and PP, while NSB is particularly effective in reducing DBP and MAP along with improving sympathovagal balance in healthy volunteers.

Reversal of muscle fatigue during 16 h of heavy intermittent cycle exercise

2004 ◽  
Vol 97 (6) ◽  
pp. 2166-2175 ◽  
Author(s):  
H. J. Green ◽  
T. A. Duhamel ◽  
S. Ferth ◽  
G. P. Holloway ◽  
M. M. Thomas ◽  
...  
Keyword(s):  
Oxygen Consumption ◽  
Muscle Fatigue ◽  
Intermittent Exercise ◽  
Low Frequency ◽  
Quadriceps Muscle ◽  
Stimulation Frequency ◽  
Peak Oxygen Consumption ◽  
Force Frequency ◽  
Reduction In Force ◽  
Before And After

This study examined the effects of extended sessions of heavy intermittent exercise on quadriceps muscle fatigue and weakness. Twelve untrained volunteers (10 men and 2 women), with a peak oxygen consumption of 44.3 ± 2.3 ml·kg−1·min−1, exercised at ∼91% peak oxygen consumption for 6 min once per hour for 16 h. Muscle isometric properties assessed before and after selected repetitions (R1, R2, R4, R7, R12, and R15) were used to quantitate fatigue (before vs. after repetitions) and weakness (before vs. before repetitions). Muscle fatigue at R1 was indicated by reductions ( P < 0.05) in peak twitch force (135 ± 13 vs. 106 ± 11 N) and by a reduction ( P < 0.05) in the force-frequency response, which ranged between ∼53% at 10 Hz (113 ± 12 vs. 52.6 ± 7.4 N) and ∼17% at 50 Hz (324 ± 27 vs. 270 ± 30 N). No recovery of force, regardless of stimulation frequency, was observed during the 54 min between R1 and R2. At R2 and for all subsequent repetitions, no reduction in force, regardless of stimulation frequency, was generally found after the exercise. The only exception was for R2, where, at 20 Hz, force was reduced ( P < 0.05) by 18%. At R15, force before repetitions for high frequencies (i.e., 100 Hz) returned to R1 (333 ± 29 vs. 324 ± 27 N), whereas force at low frequency (i.e., 10 Hz) was only partially ( P < 0.05) recovered (113 ± 12 vs. 70 ± 6.6 N). It is concluded that multiple sessions of heavy exercise can reverse the fatigue noted early and reduce or eliminate weakness depending on the frequency of stimulation.

Sign in / Sign up

Export Citation Format

Share Document