Search results for "physical exertion"
showing 10 items of 204 documents
Effects of oxygen fraction in inspired air on force production and electromyogram activity during ergometer rowing
1997
Six male rowers rowed maximally for 2500 m in ergometer tests during normoxia (fractional concentration of oxygen in inspired air, F IO2 0.209), in hyperoxia (F IO2 0.622) and in hypoxia (F IO2 0.158) in a randomized single-blind fashion. Oxygen consumption (V˙O2), force production of strokes as well as integrated electromyographs (iEMG) and mean power frequency (MPF) from seven muscles were measured in 500-m intervals. The iEMG signals from individual muscles were summed to represent overall electrical activity of these muscles (sum-iEMG). Maximal force of a stroke (F max) decreased from the 100% pre-exercise maximal value to 67 (SD 12)%, 63 (SD 15)% and 76 (SD 13)% (P<0.05 to normoxia, AN…
The influence of extra load on the mechanical behavior of skeletal muscle
1984
Eleven international jumpers and throwers engaged in year round training were divided into experimental (n = 6) and control (n = 5) groups. The experimental group was tested before and after a 3 weeks simulated hypergravity period, and again 4 weeks after the hypergravity period. The high gravity condition was created by wearing a vest weighing about 13% of the subjects body weight. The vest was worn from morning to evening including the training sessions, and only removed during sleep. The daily training of all subjects consisted of classical weight training and jumping drills. No changes in the ordinary training program were allowed in the experimental group, except for the use of the ves…
Mechanical step variability during treadmill running.
1995
The present study was designed to study intra-individual step variability measured both on vertical displacement of the body (delta Z) and on step time (delta t) parameters by means of a kinematic arm and during treadmill running. A group of 17 subjects ran successively at 60%, 80%, 100% and 140% of their maximal aerobic velocity (Vamax). The total number of steps analysed was 6116. The absolute delta Z step variability (sigma delta Z) ranged between 5 mm and 21 mm while the absolute delta t variability (sigma delta t) ranged between 6 ms and 40 ms. Step variabilities were due to step asymmetry (from 38.5% to 48.5% of the step variability) and to stride variability. For submaximal velocitie…
Differences in ground reaction forces and shock impacts between nordic walking and walking.
2014
The regular practice of Nordic walking (NW) has increased in recent years, in part thanks to the health benefits described by the scientific literature. However, there is no consensus on the effects of shock-impact absorption during its practice. Purpose: The aim of this study was to compare the levels of impact and ground reaction forces (GRF) between NW and walking (W). Method: Twenty physically active and experienced participants were assessed using a dynamometric platform and accelerometry analysis. Results: The results show statistically significantly higher levels of acceleration in the tibia (12%) and head (21%) during NW compared with W. Equally, GRF were significantly higher (27%) …
Glucocorticoid receptor expression on human B cells in response to acute heavy resistance exercise.
2011
<i>Objective:</i> To examine glucocorticoid receptor (GCR) expression on B lymphocytes in response to an acute bout of resistance exercise. <i>Methods:</i> Using a within-subject design, resistance-trained women (n = 7; age: 22.13 ± 3.09 years; height: 1.69 ± 0.084 m; body weight: 65.60 ± 10.01 kg; body mass index: 22.63 ± 2.03 kg/m<sup>2</sup>; means ± SD) and men (n = 8; age: 23.28 ± 4.26 years; height: 1.73 ± 0.086 m; body weight: 73.93 ± 12.71 kg; body mass index: 24.51 ± 2.61 kg/m<sup>2</sup>; means ± SD) performed an acute resistance exercise protocol (6 sets of 5 repetition maximum heavy squats) and a control test in a balanced, randomi…
Acute hormonal responses to two different fatiguing heavy-resistance protocols in male athletes.
1993
To examine endogenous hormonal responses to heavy-resistance exercise, ten male strength athletes performed two fatiguing but different types of sessions on separate days. In session A the loads for the leg extensor muscles in the squat-lift exercise were maximal so that the subjects performed 20 sets at 1 repetition maximum (RM) (20 x 1 RM x 100%), whereas during session B the loads were submaximal (70%) but the subjects performed each of the 10 sets until the RM (i.e., 10 repetitions/set or 10 x 10 x 70%). The recovery time between the sets was always 3 min. A decrease of 10.3 +/- 4.7% (P < 0.001) occurred in the squat-lift in 1 RM during session A, whereas session B led to a decrease…
Adaptive response of human skeletal muscle to simulated hypergravity condition
1985
The mechanical behaviour of leg extensor muscles of five international-level athletes was evaluated during 13 months training period. Drop jumps, average mechanical power during 15 S continuous jump, and vertical jumps performed with and without extra weights were used to measure explosive power characteristics. The data recorded in vertical jumps was utilized for construction of force-velocity relationship (F-V curve). The athletes did not show improvement in any of the variables studied after 12 months of intensive systematic training programme. It was assumed that the subjects already had reached their upper limit of performance. However, after that the athletes underwent a simulated 3 w…
Leg stiffness modulation during exhaustive stretch-shortening cycle exercise.
2007
The present study examined the effects of muscle activity modulation on leg stiffness during an exhaustive stretch-shortening cycle (SSC) exercise in eight male subjects. Reaction force, electromyography (EMG) of the soleus (Sol), gastrocnemius (Ga) and vastus lateralis (VL) muscles and sledge seat position were recorded during the SSC exercise, consisting of 100 maximal intermittent drop jumps followed by a continuous submaximal jumping until exhaustion, on a sledge apparatus. Metabolic loading was determined by measuring blood lactate (La). No change was found in leg stiffness during the maximal jumps, whereas the subsequent submaximal jumping induced a significant reduction by 27+/-12% (…
Reliability of knee extension and flexion measurements using the Con-Trex isokinetic dynamometer.
2007
The aim of this study was to evaluate the reliability of isokinetic and isometric assessments of the knee extensor and the flexor muscle function using the Con-Trex isokinetic dynamometer. Thirty healthy subjects (15 males, 15 females) were tested and retested 7 days later for maximal strength (isokinetic peak torque, work, power and angle of peak torque as well as isometric maximal voluntary contraction torque and rate of torque development) and fatigue (per cent loss and linear slope of torque and work across a series of 20 contractions). For both the knee extensor and the flexor muscle groups, all strength data - except angle of peak torque - demonstrated moderate-to-high reliability, wi…
Perceived physical exertion is a good indicator of neuromuscular fatigue for the core muscles
2019
Although several studies have assessed core training, specific prescription recommendations remain lacking. The purpose of the present study was to determine the association between the rate of perceived exertion (RPE) and neuromuscular fatigue of the core muscles during the prone bridging endurance test. Fifteen healthy and moderately active subjects participated. Neuromuscular fatigue was assessed with surface electromyography on the rectus abdominis (RA), external oblique, internal oblique, and lumbar erector spinae. Participants rated the RPE (Borg CR 10) every 5 s. The time to failure was 123.7 ± 58.1 s. From the midpoint of the time to failure, the RPE significantly increased (p 0.05…