Catchlike-inducing train activation of human muscle during isotonic contractions: burst modulation

Stimulation trains that exploit the catchlike property [catchlike-inducing trains (CITs)] produce greater forces and rates of rise of force than do constant-frequency trains (CFTs) during isometric contractions and isovelocity movements. This study examined the effect of CITs during isotonic contractions in healthy subjects. Knee extension was electrically elicited against a load of 10% of maximum voluntary isometric contraction. The stimulation intensity was set to produce 20% of maximum voluntary isometric contraction. The muscle was tested before and after fatigue with a 6-pulse CFT and 6-pulse CITs that contained an initial doublet, triplet, or quadruplet. For prefatigue responses, the greatest isotonic performance was produced by CITs with initial doublets. When the muscles were fatigued, triplet CITs were best. CITs produce greater excursion, work, peak power, and average power than do CFTs, because CITs produced more rapid rates of rise of force. Faster rates of rise of force enabled the preload on the muscle to be exceeded earlier during the stimulation train.

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Response to Three Weeks of Sprint Interval Training Cannot Be Explained by the Exertional Level

Medicina ◽

10.3390/medicina56080395 ◽

2020 ◽

Vol 56 (8) ◽

pp. 395

Author(s):

Raulas Krusnauskas ◽

Nerijus Eimantas ◽

Neringa Baranauskiene ◽

Tomas Venckunas ◽

Audrius Snieckus ◽

...

Keyword(s):

Average Power ◽

Lactate Concentration ◽

Training Session ◽

Blood Lactate Concentration ◽

Interval Training ◽

Knee Extension ◽

Peak Oxygen Uptake ◽

Sprint Interval Training ◽

Low Responders ◽

Before And After

Background and Objectives: The all-out mode of sprint interval training (SIT) has been shown to be an efficient method for improving sports performance, exercise capacity, and aerobic fitness. Although the benefits of SIT are well described, the mechanisms underlying the different degrees of response remain largely unexplored. We aimed to assess the effects of exertion on the responsiveness to SIT. Materials and Methods: The participants were 28 young untrained men (mean ± SD age 25.7 ± 6.03 years) who exhibited either a large or small increase in Wingate test average power in response to nine SIT sessions performed over three weeks. Each training session comprised four–six bouts of 30 s all-out cycling interspaced with 4 min of rest. Individual responses were assessed using heart rate (HR) during exercise for all nine sessions, as well as blood lactate concentration up to 1 h, and the decrement in maximal voluntary knee extension torque (MVC) up to 24 h after the first and last training sessions. Peak oxygen uptake (VO2peak) and maximum HR were measured before and after training during an incremental cycling test to exhaustion. Results: Although all participants showed benefits of SIT such as increased VO2peak, the increase in anaerobic cycling power varied between participants. We identified 17 high responders and nine low responders, whose average power outputs were 0.80 ± 0.22 and 0.22 ± 0.19 W/kg, respectively. The HR achieved during any of the training sessions did not differ between high and low responders. The lactate kinetics did not differ between groups before and after the intervention. Training resulted in a more rapid recovery of MVC without any discernible differences between the high and low responders. Conclusion: The differences in the responses to SIT are not dependent on the exertion level during training.

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Contraction-mediated inactivation of glycogen synthase is accompanied by inactivation of glycogen synthase phosphatase in human skeletal muscle

Biochemical Journal ◽

10.1042/bj2590901 ◽

1989 ◽

Vol 259 (3) ◽

pp. 901-904 ◽

Cited By ~ 10

Author(s):

Y Kida ◽

A Katz ◽

A D Lee ◽

D M Mott

Keyword(s):

Skeletal Muscle ◽

Isometric Contraction ◽

Human Skeletal Muscle ◽

Glycogen Synthase ◽

Active Form ◽

Human Muscle ◽

Maximal Voluntary Force ◽

Before And After ◽

Muscle Biopsies

Activities of glycogen synthase (GS) and GS phosphatase were determined on human muscle biopsies before and after isometric contraction at 2/3 maximal voluntary force. Total GS activity did not change during contraction (4.92 +/- 0.70 at rest versus 5.00 +/- 0.42 mmol/min per kg dry wt.; mean +/- S.E.M.), whereas both the active form of GS and the ratio of active form to total GS decreased by approximately 35% (P less than 0.01). GS phosphatase was inactivated in all subjects by an average of 39%, from 5.95 +/- 1.30 to 3.63 +/- 0.97 mmol/min per kg dry wt. (P less than 0.01). It is suggested that at least part of the contraction-induced inactivation of GS is due to an inactivation of GS phosphatase.

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Pulsed Shortwave Diathermy and Joint Mobilizations for Achieving Normal Elbow Range of Motion After Injury or Surgery With Implanted Metal: A Case Series

Journal of Athletic Training ◽

10.4085/1062-6050.49.3.45 ◽

2014 ◽

Vol 49 (6) ◽

pp. 851-855 ◽

Cited By ~ 8

Author(s):

David O. Draper

Keyword(s):

Range Of Motion ◽

Peak Power ◽

Average Power ◽

Case Series ◽

Normal Extension ◽

Therapeutic Modalities ◽

Active Range Of Motion ◽

Before And After ◽

Cubital Fossa ◽

Shortwave Diathermy

Context: Regaining full, active range of motion (ROM) after trauma to the elbow is difficult. Objective: To report the cases of 6 patients who lacked full ROM in the elbow because of trauma. The treatment regimen was thermal pulsed shortwave diathermy and joint mobilizations. Design: Case series. Setting: University therapeutic modalities laboratory. Patients or Other Participants: Six patients (5 women [83%], 1 man [17%]) lacked a mean active ROM of 24.5° of extension approximately 4.8 years after trauma or surgery. Intervention(s): Treatment consisted of 20 minutes of pulsed shortwave diathermy at 800 pulses per second for 400 microseconds (40–48 W average power, 150 W peak power) applied to the cubital fossa, immediately followed by 7 to 8 minutes of joint mobilizations. After posttreatment ROM was recorded, ice was applied to the area for about 30 minutes. Main Outcomes Measure(s): Changes in extension active ROM were assessed before and after each treatment. Once the patient achieved full, active ROM or failed to improve on 2 consecutive visits, he or she was discharged from the study. Results: By the fifth treatment, 4 participants (67%) achieved normal extension active ROM, and 2 of the 4 (50%) exceeded the norm. Five participants (83%) returned to normal activities and full use of their elbows. One month later, the 5 participants had maintained, on average, (mean ± SD) 92% ± 6% of their final measurements. Conclusions: A combination of thermal pulsed shortwave diathermy and joint mobilizations was effective in restoring active ROM of elbow extension in 5 of the 6 patients (83%) who lacked full ROM after injury or surgery.

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The effects of BCAA and creatine supplementation on anaerobic capacity and ball kicking speed in male football players

10.31083/jomh.2021.058 ◽

2021 ◽

Keyword(s):

Peak Power ◽

Average Power ◽

Anaerobic Capacity ◽

Creatine Supplementation ◽

Football Players ◽

Performance Tests ◽

Fatigue Index ◽

Tests And Measurements ◽

Before And After ◽

Branched Chain

Background and objective: The use of nutritional supplements has increased in recent years. This study analyzes the effects of Branched-Chain Amino Acids (BCAA) and creatine (CR) supplementation on anaerobic capacity and ball kicking speed in football players. Material and methods: 24 volunteer-active male amateur football players between 18--26 were recruited for this study. Football players were randomly divided into three groups as BCAA (n = 8), CR (n = 8), and placebo (PLA) (n = 8). Experimental groups were given 5 g BCAA and 2 g creatine before and after exercise, whereas the placebo group ingested bran, performance tests and measurements were performed, and results were assessed. Results: BCAA group average power (pre: 530.70 ± 53.73 W vs. post: 567.65 ± 66.68 W; p = 0.028), CR group minimum power (pre: 413.75 ± 51.13 W vs. post: 462.82 ± 71.93 W; p = 0.043) increased, while there were decreases in peak power (pre: 659.34 ± 121.03 W vs. post: 613.20 ± 124.24 W; p = 0.043) and fatigue index (pre: 6.55 ± 2.12 W/s vs. post: 4.34 ± 2.37 W/s; p = 0.043) parameters of PLA group (p < 0.05). There were statistically signiﬁcant differences in the BCAA group in rest, pre-and post-supplementation; CR group in pre-and post-supplementation; PLA group in rest, pre-and post-supplementation (p < 0.05). Conclusions: BCAA and creatine consumption do not affect recovery rates in football players regarding obtained data. But, regarding other ﬁndings of this study, BCAA and creatine supplementation improves anaerobic capacity, provides strength endurance against fatigue, and prevents the decrement of ball-kicking speed in exhaustion.

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The Effect of the Cranial Electrotherapy on the Muscle Motor Function in Different Operating Modes

SOCIETY INTEGRATION EDUCATION Proceedings of the International Scientific Conference ◽

10.17770/sie2014vol3.691 ◽

2015 ◽

Vol 3 ◽

pp. 391

Author(s):

Leonīds Čupriks ◽

Andris Rudzītis ◽

Aleksandra Čuprika ◽

Sergejs Boičenko ◽

Gundega Knipše ◽

...

Keyword(s):

Isometric Contraction ◽

Muscle Function ◽

Function Analysis ◽

Peak Torque ◽

Knee Extension ◽

Maximum Voluntary Isometric Contraction ◽

Isotonic Contraction ◽

Isokinetic Contraction ◽

Cranial Electrotherapy Stimulation ◽

Study Results

The aim of the present study was to analyze the effect of cranial electrotherapy stimulation on muscle function analysis indicators. Instrumental assessment of muscle function (on a REV9000, Technogym, Italy) was performed before and after cranial electrotherapy stimulation, assessments of the muscle function was performed during knee extension maximum voluntary, isometric contraction (MVIC), angle velocity with load 45Nm isotonic contraction and maximum pick torque in isokinetic contraction on 30°/s, 200°/s and 300°/s and neuromuscular efficiency measurements. To analyze data was used Excel program Statistics 3.1. Subjects of our study were twenty healthy athletes of sport fitness. 1 minute after cranial electrotherapy application the indicators of the analysis in 80% of cases are lower than before the cranial electrotherapy. After the application of the cranial electrotherapy the inhibition phase. 10 minutes after the cranial electrotherapy application the activation phase begins. During this phase the indicators of maximum voluntary isometric contraction increase in 41% of cases, the indicators of angle velocity with load 45Nm in isotonic contraction increase in 78% of cases and maximum peak torque indicators in isokinetic contraction on 30°/s increase in 25% of cases, on 200°/s increase in 80% of cases and on 300°/s indicators increase in 25% of cases. The results obtained in the research prove that the 20 minute effect of cranial electrotherapy stimulation partly influenced by the maximum isometric muscle strength, angular velocity and peak torque. The study results could be partially useful to optimize the different modes of operation of sports.

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Change in hamstrings flexibility: A comparison between three different manual therapeutic techniques in normal individuals

10.25259/aujmsr_4_2020 ◽

2020 ◽

Vol 2 ◽

pp. 49-51

Author(s):

Sutantar Singh ◽

Kavita Kaushal

Keyword(s):

Knee Extension ◽

Treatment Session ◽

Maximum Voluntary Isometric Contraction ◽

Normal Individuals ◽

Hamstring Muscles ◽

Before And After ◽

Group A ◽

Relaxation Maximum ◽

Mean Differences ◽

Group B

Objectives: The objectives of the study were to find the effective techniques out of post isometric relaxation, Maximum voluntary isometric contraction and PNF hold relax in increasing the flexibility of hamstring muscles. Materials and Methods: An observational study on 90 subjects (both sexes; between 18 and 30 years) was given one of three interventions – PIR, 10 Sec MVIC, and PNF HR and assigned into three groups – Group A, B, and C (each group with 30 subjects). Three repetitions of the protocol were given to each subject for regular 2 days. Active knee extension ROM was measured by the AKE test (90–90 test) before and after the treatment session both days. The data were collected, and percentage analysis was used to interpret the results. Results: All the groups showed a significant increase in active knee extension ROM. However, the results were more significant for Group B than Group A than Group C with mean differences 5.53, 4.97, and 3.83, respectively. Conclusion: Hence, it is concluded that 10 s, MVIC was the most effective among the three manual techniques.

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Midfoot Function Before and After Total Ankle Arthroplasty

Foot & Ankle International ◽

10.1177/1071100721995787 ◽

2021 ◽

pp. 107110072199578

Author(s):

Frank E. DiLiberto ◽

Steven L. Haddad ◽

Steven A. Miller ◽

Anand M. Vora

Keyword(s):

Cohort Study ◽

Prospective Cohort Study ◽

Prospective Cohort ◽

Peak Power ◽

Nonparametric Tests ◽

Total Ankle Arthroplasty ◽

Control Group ◽

Ankle Arthroplasty ◽

First Metatarsal ◽

Before And After

Background: Information regarding the effect of total ankle arthroplasty (TAA) on midfoot function is extremely limited. The purpose of this study was to characterize midfoot region motion and power during walking in people before and after TAA. Methods: This was a prospective cohort study of 19 patients with end-stage ankle arthritis who received a TAA and 19 healthy control group participants. A motion capture and force plate system was used to record sagittal and transverse plane first metatarsal and lateral forefoot with respect to hindfoot motion, as well as sagittal plane midfoot region positive and negative peak power during walking. Parametric or nonparametric tests to examine differences and equivalence across time were conducted. Comparisons to examine differences between postoperative TAA group and control group foot function were also performed. Results: Involved-limb midfoot function was not different between the preoperative and 6-month postoperative time point in the TAA group (all P ≥ .17). Equivalence testing revealed similarity in all midfoot function variables across time (all P < .05). Decreased first metatarsal and lateral forefoot motion, as well as positive peak power generation, were noted in the TAA group postoperative involved limb in comparison to the control group (all P ≤ .01). Conclusion: The similarity of midfoot function across time, along with differences in midfoot function in comparison to controls, suggests that TAA does not change midfoot deficits by 6 months postoperation. Level of Evidence: Level II, prospective cohort study.

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An Eye-Safe, SBS-Free Coherent Fiber Laser LIDAR Transmitter with Millijoule Energy and High Average Power

Photonics ◽

10.3390/photonics8010015 ◽

2021 ◽

Vol 8 (1) ◽

pp. 15

Author(s):

Mehmetcan Akbulut ◽

Leonid Kotov ◽

Kort Wiersma ◽

Jie Zong ◽

Maohe Li ◽

...

Keyword(s):

Fiber Laser ◽

Repetition Rate ◽

Peak Power ◽

Figure Of Merit ◽

Current System ◽

Glass Fibers ◽

Average Power ◽

High Gain ◽

Short Length ◽

High Average Power

We report on an eye-safe, transform-limited, millijoule energy, and high average power fiber laser. The high gain and short length of the NP phosphate-glass fibers enable the SBS-free operation with kW level peak power. The output energy is up to 1.3 mJ, and the average power is up to 23 W at an 18 kHz repetition rate with 600 ns pulses (peak power > 2.1 kW). The PER is ≈16 dB and the M2 of the beam is 1.33 × 1.18. The coherent LIDAR Figure Of Merit (FOM) is 174 mJ*sqrt(Hz), which to our knowledge is the highest reported for a fiber laser. We also report 0.75 mJ energy and >3.7 kW peak power with down to 200 ns pulses and up to 1.21 mJ energy with a 3–5 kHz repetition rate operation of the current system.

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Near-Infrared Spectroscopy for Monitoring Sternocleidomastoid Muscular Oxygenation during Isometric Flexion for Patients with Mild Nonspecific Neck Pain: A Pilot Study

Sensors ◽

10.3390/s20082197 ◽

2020 ◽

Vol 20 (8) ◽

pp. 2197

Author(s):

Chia-Chi Yang ◽

Po-Ching Yang ◽

Jia-Jin J. Chen ◽

Yi-Horng Lai ◽

Chia-Han Hu ◽

...

Keyword(s):

Infrared Spectroscopy ◽

Neck Pain ◽

Near Infrared Spectroscopy ◽

Isometric Contraction ◽

Oxidative Metabolism ◽

Near Infrared ◽

Maximum Voluntary Isometric Contraction ◽

Clinical Scenarios ◽

Wide Range ◽

Asymptomatic Individuals

Since there is merit in noninvasive monitoring of muscular oxidative metabolism for near-infrared spectroscopy in a wide range of clinical scenarios, the present study attempted to evaluate the clinical usability for featuring the modulatory strategies of sternocleidomastoid muscular oxygenation using near-infrared spectroscopy in mild nonspecific neck pain patients. The muscular oxygenation variables of the dominant or affected sternocleidomastoid muscles of interest were extracted at 25% of the maximum voluntary isometric contraction from ten patients (5 males and 5 females, 23.6 ± 4.2 years) and asymptomatic individuals (6 males and 4 females, 24.0 ± 5.1 years) using near-infrared spectroscopy. Only a shorter half-deoxygenation time of oxygen saturation during a sternocleidomastoid isometric contraction was noted in patients compared to asymptomatic individuals (10.43 ± 1.79 s vs. 13.82 ± 1.42 s, p < 0.001). Even though the lack of statically significant differences in most of the muscular oxygenation variables failed to refine the definite pathogenic mechanisms underlying nonspecific neck pain, the findings of modulatory strategies of faster deoxygenation implied that near-infrared spectroscopy appears to have practical potential to provide relevant physiological information regarding muscular oxidative metabolism and constituted convincing preliminary evidences of the adaptive manipulations rather than pathological responses of oxidative metabolism capacity of sternocleidomastoid muscles in nonspecific neck patients with mild disability.

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Impact of COVID-19 Lockdown on Serie A Soccer Players’ Physical Qualities

International Journal of Sports Medicine ◽

10.1055/a-1345-9262 ◽

2021 ◽

Author(s):

Ermanno Rampinini ◽

Federico Donghi ◽

Marco Martin ◽

Andrea Bosio ◽

Marco Riggio ◽

...

Keyword(s):

Aerobic Fitness ◽

Mixed Models ◽

Peak Power ◽

Vertical Jump ◽

Soccer Players ◽

Limited Evidence ◽

Professional Soccer ◽

Home Based ◽

Before And After ◽

Different Seasons

AbstractIn March 2020, the COVID-19 pandemic forced most activities in Italy, including soccer, to cease. During lockdown, players could only train at home, with limited evidence regarding the effect of this period. Therefore, this study aimed to investigate the effect of COVID-19 lockdown on professional soccer players’ physical performance. Aerobic fitness and vertical jump were assessed before and after four periods in two different seasons: COVID-19 lockdown, competitive period before lockdown, competitive period and summer break of the 2016–2017 season. Linear mixed models were used to examine within-period changes and between-period differences in changes observed during COVID-19 lockdown and the three other periods. Within-period changes in aerobic fitness showed a significant improvement following COVID-19 lockdown (p<0.001) and a significant decline during summer break (p<0.001). Between-period differences were significant in the comparison of COVID-19 lockdown with both the competitive 2019–2020 season (p<0.01) and summer break (p<0.001). For the vertical jump, only the between-period comparison revealed significant differences as the changes associated with COVID-19 lockdown were worse than those of the two competitive periods, for both absolute (p<0.05; p<0.001) and relative peak power (p<0.01; p<0.001). Home-based training during lockdown was effective to improve aerobic fitness, although it did not allow players to maintain their competitive period’s power levels.

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