scholarly journals Effect of Muscle Action on the Kinetic and Kinematic Behavior of the Barbell during Isoinertial Strength Assessment

2021 ◽  
Vol 11 (5) ◽  
pp. 2354
Author(s):  
Manuel Vicente Garnacho-Castaño ◽  
Juan Hernández-Lougedo ◽  
Pablo García-Fernández ◽  
José Luis Maté-Muñoz
Keyword(s):  
Power Output ◽  
Random Order ◽  
Load Test ◽  
Muscle Action ◽  
Peak Acceleration ◽  
Strength Assessment ◽  
Peak Rate ◽  
Kinematic Behavior ◽  
Key Factor ◽  
Force Time

An isoinertial strength assessment was performed to examine the kinetic and kinematic behavior of the barbell during several muscle actions. Velocity–time characteristics, force–time relationship, one repetition maximum (1RM), power output, and acceleration were compared in eccentric–concentric (EC) versus concentric only (C) sequences of the bench press (BP) and military press (MP). In two separate sessions, 28 and 29 resistance-trained athletes executed EC or C sequences in random order of the BP and MP, respectively, in an incremental load test up to their 1RM. Higher values were recorded in BP-EC than in BP-C, MP-EC, or MP-C (p < 0.01) for peak acceleration, peak rate of force development, peak rate of velocity development, and power output. Significant differences were detected between exercises in terms of the portion of the concentric phase (%) at which peak acceleration was detected, or acceleration up until peak velocity was observed (p < 0.05). No differences were observed between exercises in the portion of the concentric phase where acceleration up to the braking phase took place. The eccentric muscle action prior to concentric movement was a key factor to enhance the kinematic and kinetic performance in BP exercise. No such effects of the countermovement were produced in MP.

Oxidation of combined ingestion of glucose and fructose during exercise

2004 ◽  
Vol 96 (4) ◽  
pp. 1277-1284 ◽  
Author(s):  
Roy L. P. G. Jentjens ◽  
Luke Moseley ◽  
Rosemary H. Waring ◽  
Leslie K. Harding ◽  
Asker E. Jeukendrup
Keyword(s):  
Power Output ◽  
Statistical Significance ◽  
Random Order ◽  
Carbohydrate Oxidation ◽  
Maximum Power ◽  
The Other ◽  
Cycling Exercise ◽  
Oxidation Rates ◽  
Maximum Power Output ◽  
Exercise Period

The purpose of the present study was to examine whether combined ingestion of a large amount of fructose and glucose during cycling exercise would lead to exogenous carbohydrate oxidation rates >1 g/min. Eight trained cyclists (maximal O2consumption: 62 ± 3 ml·kg-1·min-1) performed four exercise trials in random order. Each trial consisted of 120 min of cycling at 50% maximum power output (63 ± 2% maximal O2consumption), while subjects received a solution providing either 1.2 g/min of glucose (Med-Glu), 1.8 g/min of glucose (High-Glu), 0.6 g/min of fructose + 1.2 g/min of glucose (Fruc+Glu), or water. The ingested fructose was labeled with [U-13C]fructose, and the ingested glucose was labeled with [U-14C]glucose. Peak exogenous carbohydrate oxidation rates were ∼55% higher ( P < 0.001) in Fruc+Glu (1.26 ± 0.07 g/min) compared with Med-Glu and High-Glu (0.80 ± 0.04 and 0.83 ± 0.05 g/min, respectively). Furthermore, the average exogenous carbohydrate oxidation rates over the 60- to 120-min exercise period were higher ( P < 0.001) in Fruc+Glu compared with Med-Glu and High-Glu (1.16 ± 0.06, 0.75 ± 0.04, and 0.75 ± 0.04 g/min, respectively). There was a trend toward a lower endogenous carbohydrate oxidation in Fruc+Glu compared with the other two carbohydrate trials, but this failed to reach statistical significance ( P = 0.075). The present results demonstrate that, when fructose and glucose are ingested simultaneously at high rates during cycling exercise, exogenous carbohydrate oxidation rates can reach peak values of ∼1.3 g/min.

scholarly journals Effect of Accommodating Elastic Bands on Mechanical Power Output during Back Squats

Sports ◽  
2018 ◽  
Vol 6 (4) ◽  
pp. 151 ◽  
Author(s):  
Takafumi Kubo ◽  
Kuniaki Hirayama ◽  
Nobuhiro Nakamura ◽  
Mitsuru Higuchi
Keyword(s):  
Power Output ◽  
Random Order ◽  
Mechanical Power ◽  
Muscular Force ◽  
Force Output ◽  
Elastic Band ◽  
Free Weight ◽  
Mechanical Power Output ◽  
Elastic Bands ◽  
Acceleration And Deceleration

The aim of this study was to investigate whether accommodating elastic bands with barbell back squats (BSQ) increase muscular force during the deceleration subphase. Ten healthy men (mean ± standard deviation: Age: 23 ± 2 years; height: 170.5 ± 3.7 cm; mass: 66.7 ± 5.4 kg; and BSQ one repetition maximum (RM): 105 ± 23.1 kg; BSQ 1RM/body mass: 1.6 ± 0.3) were recruited for this study. The subjects performed band-resisted parallel BSQ (accommodating elastic bands each sides of barbell) with five band conditions in random order. The duration of the deceleration subphase, mean mechanical power, and the force and velocity during the acceleration and deceleration subphases were calculated. BSQ with elastic bands elicited greater mechanical power output, velocity, and force during the deceleration subphase, in contrast to that elicited with traditional free weight (p < 0.05). BSQ with elastic bands also elicited greater mechanical power output and velocity during the acceleration subphase. However, the force output during the acceleration subphase using an elastic band was lesser than that using a traditional free weight (p < 0.05). This study suggests that BSQ with elastic band elicit greater power output during the acceleration and deceleration subphases.

scholarly journals Public Views on Priority Groups for COVID-19 Vaccination: A Survey from Iran

2021 ◽  
Vol In Press (In Press) ◽  
Author(s):  
Najmeh Moradi ◽  
Seyyed Taghi Heydari ◽  
Leila Zarei ◽  
Jalal Arabloo ◽  
Aziz Rezapour ◽  
...  
Keyword(s):  
Online Survey ◽  
Univariate Analysis ◽  
Random Order ◽  
The Elderly ◽  
Iranian Population ◽  
Vulnerable Groups ◽  
Vaccination Programs ◽  
The Family ◽  
Key Factor ◽  
Allocation Strategies

Background: In the initial coronavirus disease 2019 (COVID-19) vaccination program, prioritizing vulnerable groups is inevitable due to limited supply. Currently, most of the allocation strategies are focused on individuals’ characteristics. Objectives: The present study aimed to assess the opinions of Iranian population in specifying high-priority individuals and groups for COVID-19 vaccination. Methods: An online survey was conducted using some popular social media in Iran. The data was collected from Iranian population (878 individuals) aged 18 years and older during the COVID-19 pandemic (2 - 20 May 2020) to investigate their opinions towards vaccine allocation strategies at the family and society levels. In vaccine prioritizing within family three option and in vaccine prioritizing within society, seven population groups were introduced by the respondents in a random order, respectively. To analyze the data, mean rank and univariate analysis was used. Results: Healthcare workers, high-risk patients, and the elderly were the first priority groups for a vaccination with a mean rank of 2.8, 2.8, and 3.8, respectively. The least priority group was policymakers and executive managers (mean rank = 5.75). At the family level, 64% of the respondents introduced one of the family members as the first priority for vaccination, followed by their children (29%) and themselves (7%). No significant relationship was observed between respondents’ characteristics and their prioritization in vaccine prioritizing within society. Conclusions: Although involving public preference in decision-making is a key factor for the success of policies, careful design and implementation of vaccination programs through considering risk-benefit assessment is strongly recommended.

scholarly journals Physiological aspects and energetic contribution in 20s:10s high-intensity interval exercise at different intensities

PeerJ ◽  
2020 ◽  
Vol 8 ◽  
pp. e9791
Author(s):  
Gabriel V. Protzen ◽  
Charles Bartel ◽  
Victor S. Coswig ◽  
Paulo Gentil ◽  
Fabricio B. Del Vecchio
Keyword(s):  
Heart Rate ◽  
Blood Lactate ◽  
Power Output ◽  
High Intensity ◽  
Interval Training ◽  
Random Order ◽  
Peak Power Output ◽  
Maximal Heart Rate ◽  
Work Intensity ◽  
High Intensity Interval

Background One of the most popular high-intensity interval exercises is the called “Tabata Protocol”. However, most investigations have limitations in describing the work intensity, and this fact appears to be due to the protocol unfeasibility. Furthermore, the physiological demands and energetic contribution during this kind of exercise remain unclear. Methods Eight physically active students (21.8 ± 3.7 years) and eight well-trained cycling athletes (27.8 ± 6.4 years) were enrolled. In the first visit, we collected descriptive data and the peak power output (PPO). On the next three visits, in random order, participants performed interval training with the same time structure (effort:rest 20s:10s) but using different intensities (115%, 130%, and 170% of PPO). We collected the number of sprints, power output, oxygen consumption, blood lactate, and heart rate. Results The analysis of variance for multivariate test (number of sprints, power output, blood lactate, peak heart rate and percentage of maximal heart rate) showed significant differences between groups (F = 9.62; p = 0.001) and intensities (F = 384.05; p < 0.001), with no interactions (F = 0.94; p = 0.57). All three energetic contributions and intensities were different between protocols. The higher contribution was aerobic, followed by alactic and lactic. The aerobic contribution was higher at 115%PPO, while the alactic system showed higher contribution at 130%PPO. In conclusion, the aerobic system was predominant in the three exercise protocols, and we observed a higher contribution at lower intensities.

scholarly journals Changes in Muscle Strength in U19 Soccer Players During an Annual Training Cycle

2014 ◽  
Vol 42 (1) ◽  
pp. 175-185 ◽  
Author(s):  
Michal Lehnert ◽  
Zuzana Xaverová ◽  
Mark De Ste Croix
Keyword(s):  
Peak Torque ◽  
Quadriceps Strength ◽  
Soccer Players ◽  
Muscle Action ◽  
Strength Assessment ◽  
Training Cycle ◽  
Competitive Season ◽  
Post Hoc ◽  
Testing Range ◽  
Knee Flexors

Abstract The aim of the study was to investigate the seasonal variation in isokinetic strength of the knee flexors and extensors, and conventional (H/QCONV) and functional (H/QFUNC) hamstring to quadriceps strength ratios in highly trained adolescent soccer players. The players (n=11; age 17.8±0.3) were measured at the end of the competitive season (autumn), at the beginning and the end of pre-season (winter) and during the sixth week of a new competitive season. Isokinetic peak torque (concentric and eccentric) was measured at 60°•s-1 in a sitting position with the hip flexed at 100°. The testing range of motion was set from 10 - 90° of knee flexion. The players performed a set of five maximum repetitions for both the dominant and non-dominant leg. Statistically significant differences (p<0.001) between the four seasonal measurements were noted for peak torque of the dominant leg knee flexors in concentric muscle action only. A post hoc analysis revealed a statistically significant increase in peak torque from the 1st to the 4th measurement (p<0.001; d=0.692) and from the 2nd to the 4th (p<0.01; d=0.564). The differences in the changes of peak torque of the knee flexors and extensors depending on type of muscle action and tendencies found in the H/Q ratios throughout the annual training cycle indicate that strength assessment of the knee flexors and extensors and their balance throughout the annual training cycle could be beneficial for elite male adolescent soccer players both in terms of performance and risk of injury.

Relationship Between Isometric Force–Time Characteristics and Sprint Kayaking Performance

2020 ◽  
pp. 1-6
Author(s):  
Danny Lum ◽  
Abdul Rashid Aziz
Keyword(s):  
Bench Press ◽  
Isometric Force ◽  
Rate Of Force Development ◽  
Isometric Strength ◽  
Mean Power ◽  
Force Development ◽  
Peak Rate ◽  
Time To Completion ◽  
Strength Tests ◽  
Force Time

Force–time characteristics obtained during isometric strength tests are significantly correlated to various sporting movements. However, data on the relationship between isometric force–time characteristics and sprint kayaking performance are lacking in the literature. Purpose: The purpose of the study was, therefore, to investigate the relationship between sprint kayaking performance with ergometer performance and measures from 3 isometric strength tests: isometric squat, isometric bench press, and isometric prone bench pull. Methods: A total of 23 sprint kayaking athletes performed all 3 tests, at 90° and 120° knee angles for isometric squat and at elbow angles for isometric bench press and isometric prone bench pull, and a 200-m sprint on-water to attain the fastest time-to-completion (OWTT) possible and on a kayak ergometer to attain the highest mean power (LABTT) possible. Results: There was a significant inverse correlation between OWTT and LABTT (r = −.90, P < .001). The peak forces achieved from all isometric strength tests were significantly correlated with time-to-completion for OWTT and mean power for LABTT (r = −.44 to −.88, P < .05 and .47 to .80, P < .05, respectively). OWTT was significantly correlated with the peak rate of force development during all isometric tests except for the isometric squat at a 120° knee angle (r = −.47 to −.62, P < .05). LABTT was significantly correlated with peak rate of force development from the isometric bench press and isometric prone bench pull (r = .64–.86, P < .01). Conclusion: Based on the observed strong correlations, the mean power attained during LABTT is a good predictor of OWTT time-to-completion. Furthermore, upper- and lower-body maximum strength and peak rate of force development are equally important for on-water and ergometer sprint kayaking performance.

Field Determination of Surrounding Rock Strength under TBM Construction in Zhongtianshan Tunnel

2012 ◽  
Vol 468-471 ◽  
pp. 1771-1774 ◽  
Author(s):  
Yu Suo Wang ◽  
Zheng Qun Wu ◽  
Ming Nian Wang ◽  
Hao Chen
Keyword(s):  
Rock Strength ◽  
Point Load ◽  
Surrounding Rock ◽  
Load Test ◽  
Construction Site ◽  
Analysis Method ◽  
Work Site ◽  
Support Measures ◽  
Key Factor

Rock strength is a key factor in the tunneling efficiency of TBM construction. An issue needing special attention on the work site is how to determine rapidly and accurately the strength of the surrounding rock which makes a crucial reference for the choice of TBM tunneling parameters and corresponding support measures. In the study conducted on the TBM construction site of Zhongtianshan Tunnel, point load test (PLT) of rocks is adopted to measure the rock strength and the data is compared with those of the uniaxial compressive strength (UCS). Finally, the correlation between the two is revealed through regression analysis method.

Influence of Position and Power Output on Upper Limb Kinetics in Cycling

2016 ◽  
Vol 32 (2) ◽  
pp. 140-149 ◽  
Author(s):  
Antony Costes ◽  
Nicolas A. Turpin ◽  
David Villeger ◽  
Pierre Moretto ◽  
Bruno Watier
Keyword(s):  
Upper Limb ◽  
Power Output ◽  
Inverse Dynamics ◽  
Random Order ◽  
Standing Position ◽  
Lower Limbs ◽  
Whole Body ◽  
Sit To Stand ◽  
Shoulder Joints ◽  
Limb Kinematics

Several suggestions on the upper limb involvement in cycling exist but, to date, no study has quantified upper limb kinetics in this task. The aim of this study was to determine how crank power and pedaling position (seated or standing) affect upper limb kinetics. Handlebar loadings and upper limb kinematics were collected from 17 participants performing seated or standing pedaling trials in a random order at 6 crank powers ranging from 20% (112 ± 19 W) to 120% (675 ± 113 W) of their spontaneous sit-to-stand transition power. An inverse dynamics approach was used to compute 3D moments, powers, and works at the wrist, elbow, and shoulder joints. Over 29 parameters investigated, increases in crank power were associated with increases in the magnitudes of 23 and 20 of the kinetic variables assessed in seated and standing positions, respectively. The standing position was associated with higher magnitudes of upper limb kinetics. These results suggest that both upper and lower limbs should be considered in future models to better understand whole body coordination in cycling.

The Effects of Carbohydrate Loading on Muscle Glycogen Content and Cycling Performance

1995 ◽  
Vol 5 (1) ◽  
pp. 25-36 ◽  
Author(s):  
Laurie H.G. Rauch ◽  
Ian Rodger ◽  
Gary R. Wilson ◽  
Judy D. Belonje ◽  
Steven C. Dennis ◽  
...  
Keyword(s):  
Body Mass ◽  
Muscle Glycogen ◽  
Power Output ◽  
Glycogen Content ◽  
Potato Starch ◽  
Random Order ◽  
Cycling Performance ◽  
Muscle Glycogen Content ◽  
Glycogen Utilization ◽  
And Performance

This study compared the effects of supplementing the normal diets of 8 endurance-trained cyclists with additional carbohydrate (CHO), in the form of potato starch, for 3 days on muscle glycogen utilization and performance during a 3-hr cycle ride. On two occasions prior to the trial, the subjects ingested in random order either their normal CHO intake of 6.15 ± 0.23 g/kg body mass/day or a high-CHO diet of 10.52 ± 0.57 g/kg body mass/day. The trial consisted of 2 hr of cycling at ~75% ofwith five 60-s sprints at 100%at 20-min intervals, followed by a 60-min performance ride. Increasing CHO intake by 72 ± 9% for 3 days prior to the trial elevated preexercise muscle glycogen contents, improved power output, and extended the distance covered in 1 hr. Muscle glycogen contents were similar at the end of the 3-hr trial, indicating a greater utilization of glycogen when subjects were CHO loaded, which may have been responsible for their improved cycling performance.

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