56 research outputs found
THROWING PERFORMANCE AFTER RESISTANCE TRAINING AND DETRAINING
Terzis, G, Stratakos, G, Manta, P, and Georgiadis, G. Throwing
performance after resistance training and detraining. J Strength Cond
Res 22: 1198-1204, 2008-The purpose of the present study was to
investigate the effect of short-term resistance training and detraining
on shot put throwing performance. Eleven young healthy subjects with
basic shot put skills participated in 14 weeks of resistance training,
which was followed by 4 weeks of detraining. Shot put performance in
four field tests was measured before (T1) and after (T2) resistance
training and after detraining (T3). At the same time points, one
repetition maximum (1RM) was measured in squat, bench press, and leg
press. Fat-free mass (FFM) was determined with dual x-ray absorptiometry
and muscle biopsies obtained from vastus lateralis for the determination
of fiber type composition and cross-sectional area (CSA). 1RM strength
increased 22-34% (p < 0.01) at T2 and decreased 4-5% (not
significantly different) at T3. Shot put performance increased 6-12% (p
< 0.05) after training and remained unaltered after detraining. FFM
increased at T2 (p < 0.05) but remained unchanged between T2 and T3.
Muscle fiber CSA increased 12-18% (p < 0.05) at T2. Type I muscle fiber
CSA was not altered after detraining, but type IIa and IIx fiber CSA was
reduced 10-12% (p < 0.05). The percentage of type IIx muscle fibers was
reduced after training (T1 = 18.7 +/- 4, T2 = 10.4 +/- 1; p < 0.05), and
it was increased at T3 compared with T2 (T3 = 13.7 +/- 1; p < 0.05).
These results suggest that shot put performance remains unaltered after
4 weeks of complete detraining in moderately resistance-trained
subjects. This might be linked to the concomitant reduction of muscle
fiber CSA and increase in the percentage of type IIx muscle fibers
Gastrocnemius Medialis Architectural Properties at Rest and During Stretching in Female Athletes with Different Flexibility Training Background
Background: This study examined gastrocnemius medialis (GM) architectural properties and ankle joint range of motion (ROM) between female athletes with different flexibility training background. Methods: Elite rhythmic gymnasts (n = 10) were compared to national level volleyball athletes (n = 10). Fascicle length, pennation angle and muscle thickness at the medial and the distal part of GM, and ankle ROM were measured at rest and during 1 min of static stretching. Results: At rest, rhythmic gymnasts displayed longer fascicles compared to volleyball athletes, at the medial (5.93 ± 0.27 vs. 4.74 ± 0.33 mm, respectively, p = 0.001) and the distal part of GM (5.63 ± 0.52 vs. 4.57 ± 0.51 mm, respectively, p = 0.001), smaller pennation angle at the medial part (22.4 ± 2.5 vs. 25.8 ± 2.4°; respectively, p = 0.001) and greater ankle angle (121.7 ± 4.1 vs. 113.2 ± 3.7°, respectively, p = 0.001). During the 1 min of static stretching, gymnasts displayed greater fascicle elongation at the distal part (p = 0.026), greater maximal ankle dorsiflexion (p < 0.001) and muscle tendon junction displacement (p < 0.001) with no difference between groups in pennation angles (p > 0.145), muscle thickness (p > 0.105), and fascicle elongation at mid-belly (p = 0.063). Conclusions: Longer muscle fascicles at rest and greater fascicle elongation at the distal part of GM may contribute to the greater ankle ROM observed in rhythmic gymnasts
MUSCLE FIBRE TYPE COMPOSITION AND BODY COMPOSITION IN HAMMER THROWERS
Aim of the present study was to describe the muscle fibre type composition and body composition of well-trained hammer throwers. Six experienced hammer throwers underwent the following measurements: one repetition maximum in squat, snatch, and clean, standing broad jump, backward overhead shot throw and the hammer throw. Dual x-ray absorptiometry was used for body composition analysis. Fibre type composition and cross sectional area was determined in muscle biopsy samples of the right vastus lateralis. Eight physical education students served as a control group. One repetition maximum in squat, snatch and clean for the hammer throwers was 245 ± 21, 132 ± 13 and 165 ± 12kg, respectively. Lean body mass was higher in hammer throwers (85.9 ± 3. 9kg vs. 62.7 ± 5.1kg (p < 0.01). The percentage area of type II muscle fibres was 66.1 ± 4% in hammer throwers and 51 ± 8% in the control group (p < 0.05). Hammer throwers had significantly larger type IIA fibres (7703 ± 1171 vs. 5676 ± 1270μm2, p < 0.01). Hammer throwing performance correlated significantly with lean body mass (r = 0.81, p < 0.05). These data indicate that hammer throwers have larger lean body mass and larger muscular areas occupied by type II fibres, compared with relatively untrained subjects. Moreover, it seems that the enlarged muscle mass of the hammer throwers contributes significantly to the hammer throwing performanc
The Acute Effects of Plyometric Exercises on Sprint Performance and Kinematics
Background: Post-activation potentiation refers to the acute and temporary enhancement of performance in explosive movements after performing a conditioning activity, such as plyometrics. The current study aimed to investigate the acute effects of horizontal leg bounding on 30 m acceleration performance, 5 m split times, and sprint kinematics (step frequency and length, flight and contact time). Methods: Fourteen young sprinters, nine females and five males, performed two experimental conditions and one control condition in randomized and crossover orders. The experimental conditions included 3 × 10 repetitions of alternate-leg horizontal bounding or 3 × 5 repetitions of single-leg horizontal bounding for each leg. Active recovery was performed in the control condition. A 30 m sprint test was executed before and 5 min after each condition. Results: Sprint times at 5 m (p = 0.014) and 10 m (p = 0.041) were improved after performing alternate-leg horizontal bounding. Additionally, an increase in running velocity (p = 0.017) and step frequency (p = 0.028) was observed in the 0–5 m segment of the sprint. Sprint performance and kinematics showed no significant differences after performing single-leg horizontal bounding. Conclusions: Alternate-leg horizontal bounding, which is a sprint-specific exercise that emphasizes a horizontal impulse, can be used effectively to improve performance in the initial phase of sprint acceleration
FIBER TYPE COMPOSITION AND CAPILLARY DENSITY IN RELATION TO SUBMAXIMAL NUMBER OF REPETITIONS IN RESISTANCE EXERCISE
The purpose of this study was to investigate the relationship between
skeletal muscle fiber type composition and the maximum number of
repetitions performed during submaximal resistance exercise. Twelve
young men performed a maximum repetitions test at 85% of 1 repetition
maximum (1RM) in the leg press, which was repeated after 1 week. Seven
days after the second 85% 1RM test, they performed a maximum
repetitions test at 70% of 1RM in the leg press. This test, at 70%
1RM, was repeated 7 days later. One week before the initiation of the
testing sessions, a biopsy sample was obtained from the vastus lateralis
muscle and analyzed for fiber type distribution, fiber cross-sectional
area, and capillary density (capillaries.mm(-2)). A low and
nonsignificant relationship was found between the fiber type
distribution or percent fiber type area and the number of repetitions
performed at either 70% or 85% 1RM. Moreover, the number of
repetitions performed at 70% or 85% of 1RM was not related
significantly with 1RM strength. In contrast, the number of repetitions
performed at 70% 1RM was significantly correlated with the number of
capillaries per mm(2) of muscle cross-sectional area (r = 0.70; p =
0.01). These results suggest that fiber type composition is not the
major biological variable regulating the number of repetitions performed
in submaximal resistance exercise. Rather, it seems that submaximal
strength performance depends on muscle capillary density, which is
linked with the endurance capacity of the muscle tissue
Lean Body Mass, Muscle Architecture, and Performance in Well-Trained Female Weightlifters
Lean mass and quadriceps muscle architecture have been associated with performance in male well-trained weightlifters, but no data exist for female weightlifters. The aim of the study is to investigate the relationship between lean mass, quadriceps cross sectional area (CSA), and muscle architecture with weightlifting performance in female weightlifters. Eight well-trained female weightlifters (age 23.5 ± 6.3 years, maximum total lifting performance = 147.4 ± 34.1 kg) participated in the study. Five of the athletes were members of the national team and three were among the nation’s top-five performers of the respective body-weight category. Measurements included maximum lifting performance in snatch and clean and jerk, body composition (dual x-ray absorptiometry), vastus lateralis (VL) muscle architecture, vastus intermedius (VI) muscle thickness and quadriceps muscles’ CSA and countermovement jump (CMJ). Very large to nearly perfect correlations were found between snatch and clean and jerk for trunk lean body mass (r = 0.959 and 0.929), for total CSA (r = 0.732 and 0.608), and CMJ power (r = 0.933 and 0.896). These results suggest that lean body mass, quadriceps’ CSA and CMJ should be monitored regularly in female weightlifters to detect potential modifications in lifting performance
Exercise-Induced Changes in Tumor Growth via Tumor Immunity
Immunity in the tumor microenvironment plays a central role in tumor development. Cytotoxic immune cells act against tumors, while tumors manage to trigger immunosuppressive mechanisms for defense. One bout of physical exercise acutely regulates the immune system inducing short-term redistribution of immune cells among body organs. Repeated acute immune cell mobilization with continuing exercise training results in long-term adaptations. These long-term exercise-induced changes in the immune system arise both in healthy and in diseased populations, including cancer patients. Recent preclinical studies indicate that physical exercise may have a positive impact on intra-tumoral immune cell processes, resulting in tumor suppression. This short narrative review describes the effect of physical exercise on tumor growth as detected via changes in tumor immunity. Research evidence shows that exercise may improve tumor-suppressive functions and may reduce tumor-progressive responses and mechanisms of immune cells, controlling tumor development. Specifically, it seems that exercise in rodents triggers shifts in tumor infiltration of macrophages, neutrophils, natural killer cells, cytotoxic and regulatory T lymphocytes, resulting in tumor suppression. These recent promising data suggest that physical exercise could be combined with anticancer immunotherapies, although exercise parameters like intensity, duration, and frequency need to be evaluated in more detail. More research is needed to investigate the effect of exercise in other immune cell subtypes and their possible connection with tumor growth, whilst information from human tumors is also required. Copyright: © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/)
Muscle Ultrasound Echo Intensity and Fiber Type Composition in Young Females
Ultrasonography has been extensively used to evaluate skeletal muscle morphology. The echo intensity, i.e., the mean pixel intensity of a specific region of interest in an ultrasound image, may vary among muscles and individuals with several intramuscular parameters presumed to influence it. The purpose of this study was to investigate the correlation between muscle echo intensity and muscle fiber type composition in humans. Thirteen female physical education students (age: 22.3 ± 5.4 years, height: 1.63 ± 0.06 m, body mass: 59.9 ± 7.4 kg) with no history of systematic athletic training participated in the study. Body composition with dual X-ray absorptiometry, leg-press maximum strength (1-RM), echo intensity, and the cross-sectional area (CSA) of the vastus lateralis (VL) muscle according to ultrasonography were measured. Muscle biopsies were harvested from the VL site where the echo intensity was measured. VL echo intensity was not significantly correlated with the percentage of type I muscle fibers or with the percentage area of type I muscle fibers. However, when VL echo intensity was corrected for the subcutaneous fat thickness at the site of the measurement, it was significantly correlated with the percentage of type I muscle fibers (r = 0.801, p p < 0.01). These results suggest that the echo intensity of the vastus lateralis muscle corrected for the subcutaneous fat thickness at the measurement site may provide an estimate of the muscle fiber type composition, at least in young moderately trained females
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