Refine
Year of publication
Document Type
- Article (191)
- Postprint (91)
- Review (15)
- Other (9)
- Monograph/Edited Volume (1)
- Conference Proceeding (1)
Is part of the Bibliography
- yes (308) (remove)
Keywords
- football (26)
- resistance training (19)
- adolescents (17)
- athletic performance (14)
- exercise (14)
- youth (14)
- balance (13)
- performance (11)
- strength training (11)
- stretch-shortening cycle (11)
- training (11)
- children (10)
- monitoring (10)
- muscle strength (10)
- training load (10)
- postural control (9)
- power (9)
- Exercise (8)
- Gait (8)
- electromyography (8)
- elite athletes (8)
- gait (8)
- injury risk (8)
- strength (8)
- young athletes (8)
- plyometric training (7)
- Stretch-shortening cycle (6)
- aging (6)
- muscle power (6)
- physical fitness (6)
- physiology (6)
- postural stability (6)
- Electromyography (5)
- Ground reaction force (5)
- Resistance training (5)
- force (5)
- injury (5)
- jumping (5)
- movement (5)
- periodization (5)
- plyometric exercise (5)
- recovery (5)
- speed (5)
- sport-specific performance (5)
- striking combat sports (5)
- working memory (5)
- youth sports (5)
- Aging (4)
- Balance (4)
- EMG (4)
- Performance (4)
- Team sports (4)
- Youth (4)
- agility (4)
- change of direction (4)
- elderly (4)
- global positioning system (4)
- ground reaction force (4)
- human physical conditioning (4)
- inertial measurement unit (4)
- loading rate (4)
- modality compatibility (4)
- muscle (4)
- physical performance (4)
- postural sway (4)
- rate of perceived exertion (4)
- rolling averages (4)
- running (4)
- sensitivity (4)
- soccer (4)
- validity (4)
- weighted moving averages (4)
- Body composition (3)
- COVID-19 (3)
- EEG (3)
- Fatigue (3)
- Physical fitness (3)
- Postural stability (3)
- Power (3)
- RPE (3)
- Seniors (3)
- Trunk muscle strength (3)
- Walking (3)
- adolescent (3)
- apoptosis (3)
- attentional demand (3)
- biomechanics (3)
- cardiomyopathy (3)
- cardiorespiratory fitness (3)
- child (3)
- cognitive performance (3)
- cognitive-postural dual task (3)
- diabetes (3)
- dual task (3)
- fatigue (3)
- gait analysis (3)
- ground reaction forces (3)
- hospitalization (3)
- maturation (3)
- maturity (3)
- miRNAs (3)
- motor skills (3)
- musculoskeletal and neural physiological phenomena (3)
- oarsmen (3)
- on-water performance (3)
- overreaching (3)
- overtraining (3)
- peak height velocity (3)
- physical conditioning human (3)
- plyometrics (3)
- range of motion (3)
- rate of torque development (3)
- reliability (3)
- running mechanics (3)
- somatic variables (3)
- talent (3)
- youth athletes (3)
- youth soccer (3)
- ACWR (2)
- Acceleration (2)
- Acute Recovery and Stress Scale (ARSS) (2)
- Children (2)
- Cognitive fatigue (2)
- Cognitive interference (2)
- Cognitive/motor interference (2)
- Computer Software (2)
- Conditioning activity (2)
- Countermovement jump (2)
- Crossover (2)
- DXA (2)
- Daily life (2)
- Detraining (2)
- EMOTIKON (2)
- Exertion (2)
- Flat feet (2)
- Football (2)
- Footwear (2)
- Ginkgo biloba extract (2)
- Healthy aging (2)
- Injury risk (2)
- Jugendliche (2)
- Jump height (2)
- Kampfsport (2)
- Kinder (2)
- Kinematics (2)
- Linear regression analysis (2)
- Maximalkraft (2)
- Mobility (2)
- Motion (2)
- Muscle (2)
- Muscle mass (2)
- Muscle power (2)
- Muscle strength (2)
- OptoGait (2)
- Overhead athletes (2)
- Postural control (2)
- Principal component analysis (2)
- Proactive/reactive balance (2)
- RGB-D cameras (2)
- Recovery (2)
- Repeated sprint (2)
- Scanning electron microscopy (2)
- Schnellkraft (2)
- Short‐term effect (2)
- Shoulder (2)
- Single/dual tasking (2)
- Speed (2)
- Sport-specific performance (2)
- Steady-state balance (2)
- Stress levels (2)
- Sway (2)
- Swimming performance (2)
- Tiredness (2)
- Velocity (2)
- Widerstandstraining (2)
- Young swimmers (2)
- Zebris (2)
- academy (2)
- acute chronic workload ratio (2)
- aerobic exercise (2)
- aerobic metabolism (2)
- aerobic power (2)
- allometry (2)
- alpha-2 (2)
- ankles (2)
- anterior cruciate ligament (2)
- anthropometry (2)
- anxiety (2)
- balance training (2)
- barbell velocity (2)
- biological age (2)
- biological maturation (2)
- blood (2)
- blood sample (2)
- body density (2)
- body limbs (2)
- body shape (2)
- calcaneal eversion (2)
- canoe racing (2)
- change of direction speed (2)
- change-of-direction speed (2)
- cognitive interference (2)
- cognitive/muscular fatigue (2)
- combat sport (2)
- comparison of devices (2)
- concurrent training (2)
- conditioning activity (2)
- conditioning exercise (2)
- core strength (2)
- cross-education (2)
- data pipeline (2)
- depression (2)
- diabetes mellitus (2)
- diabetic (2)
- digital health (2)
- drop jump (2)
- dual-task costs (2)
- early sport specialization (2)
- eccentric-plyometric (2)
- endurance performance (2)
- evaluation (2)
- exercise intervention (2)
- exercise test (2)
- exercise training (2)
- external load (2)
- external training load (2)
- eyedness (2)
- fMRI (2)
- feet (2)
- fitness tests (2)
- flat feet (2)
- footedness (2)
- force production (2)
- functional performance (2)
- gait analysis algorithm (2)
- gait speed (2)
- gender differences (2)
- hamstring muscles (2)
- heart rate (2)
- hematocrit (2)
- high-intensity-interval training (2)
- hip (2)
- hormones (2)
- human motion (2)
- immune system (2)
- internal load (2)
- jump performance (2)
- jump training (2)
- jumps (2)
- kinetics (2)
- knee joint angle (2)
- knee osteoarthritis (2)
- knees (2)
- late childhood (2)
- latency (2)
- laterality (2)
- limb overuse conditions (2)
- linear sprint (2)
- long-term (2)
- low-back-pain (2)
- lower limb mechanics (2)
- lower-extremity kinematics (2)
- martial arts (2)
- matched time (2)
- material fatigue (2)
- medial longitudinal arch (2)
- mental imagery (2)
- meta-analysis (2)
- methodological quality (2)
- mitochondrial adaptation (2)
- mobility disability (2)
- motion capture (2)
- motor-performance (2)
- muscle activation (2)
- muscle fitness (2)
- muscle metabolism (2)
- muscular endurance (2)
- muscular strength (2)
- of-direction speed (2)
- oxygen consumption (2)
- passive stretching (2)
- peak torque (2)
- pelvic alignment (2)
- pervasive healthcare (2)
- physical fitness expertise (2)
- physiological strain (2)
- postural balance (2)
- power training (2)
- prevention (2)
- public dataset (2)
- race time (2)
- randomized controlled-trial (2)
- responses (2)
- return-to-sport (2)
- rotation (2)
- rugby league players (2)
- schedule (2)
- scholastic demands (2)
- school baseball players (2)
- sensorimotor training (2)
- sex-differences (2)
- skeletal joints (2)
- specific assessment (2)
- specificity (2)
- sportliche Leistung (2)
- sports (2)
- sprint (2)
- sprinting (2)
- sprints (2)
- stability (2)
- standing position (2)
- taekwondo electronic scoring system (2)
- taekwondo-specific testing (2)
- tasks (2)
- team sport (2)
- theta (2)
- time-efficient exercise (2)
- track and field (2)
- training adaptation (2)
- twitch torque (2)
- unstable walkway (2)
- virus infection (2)
- water sports (2)
- weight lifting (2)
- weight loss (2)
- weight training (2)
- weightlifting (2)
- whole-body vibratoin (2)
- women (2)
- work-rate distribution (2)
- young soccer players (2)
- youth sport (2)
- Accelerometer (1)
- Alpha-2 (1)
- Association (1)
- Athlete testing (1)
- Attention (1)
- Balance Tests (1)
- Biomechanics (1)
- Bow leg (1)
- Cardiorespiratory endurance (1)
- Central activation (1)
- Cognition motor (1)
- Cognitive enhancer (1)
- Cognitive skills (1)
- Cohort study (1)
- Core stability (1)
- Core strength (1)
- Cross-over fatigue (1)
- Crossover fatigue (1)
- Developmental gains (1)
- Dual tasks (1)
- EXERCISE (1)
- Elderly (1)
- Electric stimulation (1)
- Electroencephalography (EEG) (1)
- Electromyography (EMG) (1)
- Elite sports (1)
- Endocrine (1)
- Endurance (1)
- Executive function (1)
- Exercise therapy (1)
- Exhaustion (1)
- Explosive force production (1)
- Fall risk (1)
- Fall risk assessment (1)
- Falls (1)
- Field test (1)
- Flexibility (1)
- Force (1)
- Force production (1)
- Frail elderly (1)
- Free moment (1)
- Functional magnetic resonance imaging (fMRI) (1)
- Gait biomechanics (1)
- Gait kinematics (1)
- Gait kinetics (1)
- Gym-based/home-based training (1)
- Health care (1)
- ICA (1)
- Instability (1)
- Intensity Dose -response relationship (1)
- Isokinetic (1)
- Judo-specific pulling movement (1)
- Jumping height (1)
- Keyage children (1)
- Kindergarten (1)
- Knee valgus (1)
- Knee valgus motion (1)
- Lateral jumps (1)
- Linear Mixed Models (1)
- Linear mixed models (1)
- Loading rate (1)
- Lower-extremity muscle power (1)
- MUSCLE (1)
- Maturation (1)
- Maximal isometric force (1)
- Maximal voluntary contraction (MVC) (1)
- Mental fatigue (1)
- Metabolism (1)
- Mild cognitive impairment (1)
- Morote-seoi-nage (1)
- Motor function (1)
- Motor performance (1)
- Motor skills (1)
- Movement velocity (1)
- Multiple sclerosis (1)
- Muscle contraction (1)
- Muscle torque (1)
- Neural inhibition (1)
- Oberflächenelektromyografie (1)
- Older-than-keyage children (1)
- Optojump system (1)
- Paediatrics (1)
- Parkinson's disease (1)
- Pediatric gait (1)
- Performance gains (1)
- Physical Fitness (1)
- Physical performance (1)
- Physiology (1)
- Plyometric exercise (1)
- Plyometrics (1)
- Post-activation potentiation (1)
- Postactivation potentiation (1)
- Postural Control (1)
- Postural balance (1)
- Power training (1)
- Preventive therapy (1)
- Primary school (1)
- Primary school children (1)
- Quadriceps muscle (1)
- Quadriceps strength (1)
- Quarantine (1)
- Reactive movement (1)
- Reflex (1)
- Sars-CoV-2 (1)
- Sensorimotor training (1)
- Skill (1)
- Squat jump (1)
- Strength training (1)
- Stress (1)
- Theraband training (1)
- Theta (1)
- Transcranial magnetic brain stimulation (TMS) (1)
- Vertec device (1)
- WALKING (1)
- Walking speed (1)
- Work ability (1)
- activities (1)
- adolescent athletes (1)
- age (1)
- annual training (1)
- assessment (1)
- athlete testing (1)
- athlete. (1)
- athletes (1)
- athletic (1)
- attention (1)
- balance strategy (1)
- ball speed (1)
- ballistic training (1)
- blood lactate (1)
- blood lactate; (1)
- bone (1)
- boys (1)
- causal mediation analysis (1)
- climbing (1)
- cognitive enhancer (1)
- cognitive function (1)
- cognitive skills (1)
- cognitive/motor interference (1)
- combat sports (1)
- conditioning stimulus (1)
- congested calendar (1)
- core (1)
- crosstalk (1)
- deconditioning (1)
- detraining (1)
- directed acyclic graphs (1)
- dominant limb (1)
- dose response (1)
- dose-response relation (1)
- dose-response relationship (1)
- electroencephalography (1)
- elite (1)
- elite sport (1)
- endocrine (1)
- endurance (1)
- energetic systems (1)
- executive control (1)
- executive function (1)
- exercise prescription (1)
- exhaustion (1)
- explosive force production (1)
- fall risk assessment (1)
- field test (1)
- fitness (1)
- flat foot (1)
- flexibility (1)
- footwear (1)
- free moment (1)
- function (1)
- fundamental movement skill (1)
- gender (1)
- girls (1)
- hearing loss (1)
- high effect size (1)
- high-intensity interval training (1)
- impact loading (1)
- infection (1)
- injury prevention (1)
- instability resistance training (1)
- intermittent sport (1)
- intervention (1)
- jump (1)
- jump height (1)
- jump height/power (1)
- jump performances (1)
- jump/sprint exercises (1)
- jumping ability (1)
- kindergarten (1)
- knee (1)
- knee flexion angle (1)
- knee valgus angle (1)
- knee valgus motion (1)
- leg extensors (1)
- load carriage (1)
- load-velocity (1)
- load–velocity relationship (1)
- locomotor skill (1)
- maximal isometric contraction (1)
- maximal isometric torque (1)
- maximal strength (1)
- maximum voluntary contraction (1)
- metabolism (1)
- mild cognitive impairment (1)
- motivational climate (1)
- motor performance (1)
- motor skill (1)
- muscle activity (1)
- muscle coactivation (1)
- muscular power (1)
- musculature (1)
- myofascial (1)
- neuromuscular rolling (1)
- non-dominant limb (1)
- of daily living (1)
- optimal load (1)
- patients (1)
- performance gains (1)
- physical activity (1)
- physical activity program (1)
- physical fitness test (1)
- post-activation potentiation (1)
- practice (1)
- preactivation (1)
- pressure (1)
- primary school (1)
- proactive/reactive balance (1)
- progression (1)
- proprioception (1)
- race (1)
- rate of force development (1)
- rating of perceived exertion (1)
- reactive movement (1)
- reflex (1)
- region/point elastic gym floor (1)
- relationship (1)
- relationships (1)
- running velocity (1)
- sedentary (1)
- self massage (1)
- self-massage therapy (1)
- self-myofascial release (1)
- seniors (1)
- sensory input (1)
- shoe (1)
- short latency response (1)
- shoulder girdle (1)
- shoulder strength (1)
- single/dual tasking (1)
- ski jumping (1)
- skill (1)
- snatch (1)
- soccer players (1)
- specific strength training (1)
- spezifisches Krafttraining (1)
- sport profile (1)
- static/dynamic postural control (1)
- steady-state balance (1)
- stroke (1)
- structured (1)
- surface electromyography (1)
- task difficulty (1)
- tendon stiffness (1)
- test-retest reliability (1)
- therapy (1)
- time (1)
- time series analysis (1)
- torque (1)
- training intensity (1)
- training intervention (1)
- training specificity (1)
- vertical jump height (1)
- vestibular (1)
- virus (1)
- walking (1)
- walking capacity (1)
- walking speed (1)
- work (1)
- young (1)
- young adults (1)
Institute
- Department Sport- und Gesundheitswissenschaften (143)
- Strukturbereich Kognitionswissenschaften (104)
- Humanwissenschaftliche Fakultät (22)
- Extern (14)
- Department Psychologie (8)
- Hasso-Plattner-Institut für Digital Engineering GmbH (6)
- Fakultät für Gesundheitswissenschaften (3)
- Mathematisch-Naturwissenschaftliche Fakultät (3)
- Fachgruppe Soziologie (1)
- Hasso-Plattner-Institut für Digital Engineering gGmbH (1)
Associations between measures of physical fitness and cognitive performance in preschool children
(2022)
Background:
Given that recent studies report negative secular declines in physical fitness, associations between fitness and cognition in childhood are strongly discussed. The preschool age is characterized by high neuroplasticity which effects motor skill learning, physical fitness, and cognitive development. The aim of this study was to assess the relation of physical fitness and attention (including its individual dimensions (quantitative, qualitative)) as one domain of cognitive performance in preschool children. We hypothesized that fitness components which need precise coordination compared to simple fitness components are stronger related to attention.
Methods:
Physical fitness components like static balance (i.e., single-leg stance), muscle strength (i.e., handgrip strength), muscle power (i.e., standing long jump), and coordination (i.e., hopping on one leg) were assessed in 61 healthy children (mean age 4.5 +/- 0.6 years; girls n = 30). Attention was measured with the "Konzentrations-Handlungsverfahren fur Vorschulkinder" [concentration-action procedure for preschoolers]). Analyses were adjusted for age, body height, and body mass.
Results:
Results from single linear regression analysis revealed a significant (p < 0.05) association between physical fitness (composite score) and attention (composite score) (standardized ss = 0.40), showing a small to medium effect (F-2 = 0.14). Further, coordination had a significant relation with the composite score and the quantitative dimension of attention (standardized ss = 0.35; p < 0.01; standardized ss = - 0.33; p < 0.05). Coordination explained about 11% (composite score) and 9% (quantitative dimension) of the variance in the stepwise multiple regression model.
Conclusion:
The results indicate that performance in physical fitness, particularly coordination, is related to attention in preschool children. Thus, high performance in complex fitness components (i.e., hopping on one leg) tends to predict attention in preschool children. Further longitudinal studies should focus on the effectiveness of physical activity programs implementing coordination and complex exercises at preschool age to examine cause-effect relationships between physical fitness and attention precisely.
The purpose of this study was to compare the effects of combined resistance and plyometric/sprint training with plyometric/sprint training or typical soccer training alone on muscle strength and power, speed, change-of-direction ability in young soccer players. Thirty-one young (14.5 ± 0.52 years; tanner stage 3–4) soccer players were randomly assigned to either a combined- (COMB, n = 14), plyometric-training (PLYO, n = 9) or an active control group (CONT, n = 8). Two training sessions were added to the regular soccer training consisting of one session of light-load high-velocity resistance exercises combined with one session of plyometric/sprint training (COMB), two sessions of plyometric/sprint training (PLYO) or two soccer training sessions (CONT). Training volume was similar between the experimental groups. Before and after 7-weeks of training, peak torque, as well as absolute and relative (normalized to torque; RTDr) rate of torque development (RTD) during maximal voluntary isometric contraction of the knee extensors (KE) were monitored at time intervals from the onset of contraction to 200 ms. Jump height, sprinting speed at 5, 10, 20-m and change-of-direction ability performances were also assessed. There were no significant between–group baseline differences. Both COMB and PLYO significantly increased their jump height (Δ14.3%; ES = 0.94; Δ12.1%; ES = 0.54, respectively) and RTD at mid to late phases but with greater within effect sizes in COMB in comparison with PLYO. However, significant increases in peak torque (Δ16.9%; p < 0.001; ES = 0.58), RTD (Δ44.3%; ES = 0.71), RTDr (Δ27.3%; ES = 0.62) and sprint performance at 5-m (Δ-4.7%; p < 0.001; ES = 0.73) were found in COMB without any significant pre-to-post change in PLYO and CONT groups. Our results suggest that COMB is more effective than PLYO or CONT for enhancing strength, sprint and jump performances.
Background: Cross-sectional studies detected associations between physical fitness, living area, and sports participation in children. Yet, their scientific value is limited because the identification of cause-and-effect relationships is not possible. In a longitudinal approach, we examined the effects of living area and sports club participation on physical fitness development in primary school children from classes 3 to 6.
Methods: One-hundred and seventy-two children (age: 9-12 years; sex: 69 girls, 103 boys) were tested for their physical fitness (i.e., endurance [9-min run], speed [50-m sprint], lower- [triple hop] and upper-extremity muscle strength [1-kg ball push], flexibility [stand-and-reach], and coordination [star coordination run]). Living area (i.e., urban or rural) and sports club participation were assessed using parent questionnaire.
Results: Over the 4 year study period, urban compared to rural children showed significantly better performance development for upper- (p = 0.009, ES = 0.16) and lower-extremity strength (p < 0.001, ES = 0.22). Further, significantly better performance development were found for endurance (p = 0.08, ES = 0.19) and lower-extremity strength (p = 0.024, ES = 0.23) for children continuously participating in sports clubs compared to their non-participating peers.
Conclusions: Our findings suggest that sport club programs with appealing arrangements appear to represent a good means to promote physical fitness in children living in rural areas.
The purpose of this study was to assess intrasession and intersession reliability of maximal and explosive isometric torque production of the elbow flexors and its respective neuromuscular activation pattern. Subjects (13 men, age: 24.8 +/- 3.1 years, height: 1.9 +/- 0.1 m, body mass: 83.7 +/- 12.7 kg; and 6 women, age: 26.5 +/- 1.4 years, height: 1.7 +/- 0.1 m, body mass: 62.7 +/- 7.0 kg) were tested and retested 2-7 days later performing unilateral maximal isometric elbow flexions. Absolute (coefficient of variation[CV], test-retest variability[TRV], Bland-Altman plots with 95% limits of agreement) and relative reliability statistics (intraclass correlation coefficient) were calculated for various mechanical (i.e., maximal isometric torque, rate of torque development, impulse) and electromyographical measures (i.e., mean average voltage) at different time intervals relative to onset of torque (i. e., 30, 50, 100, 200, 300, 400, 100-200 ms). Intraclass correlation coefficient values were >= 0.61 for all mechanical and electromyographical measures and time intervals indicating good to excellent intrasession and intersession reliability. BlandAltman plots confirmed these findings by showing that only 0-2 (<= 3.3%) data points were beyond the limits of agreement. Regarding torque and electromyographic measures, CV (11.9-32.3%) and TRV (18.4-53.8%) values were high during the early intervals of torque development (<= 100 ms) indicating high variability. During the later intervals (>100 ms), lower CV (i. e., 5.0-29.9%) and TRV values (i.e., 5.4-34.6%) were observed indicating lower variability. The present study revealed that neuromuscular performance during explosive torque production of the elbow flexors is reproducible in time intervals >100 ms after onset of isometric actions, whereas during earlier time intervals variability is high.
Validation of two accelerometers to determine mechanical loading of physical activities in children
(2015)
The purpose of this study was to assess the validity of accelerometers using force plates (i.e., ground reaction force (GRF)) during the performance of different tasks of daily physical activity in children. Thirteen children (10.1 (range 5.4-15.7)years, 3 girls) wore two accelerometers (ActiGraph GT3X+ (ACT), GENEA (GEN)) at the hip that provide raw acceleration signals at 100Hz. Participants completed different tasks (walking, jogging, running, landings from boxes of different height, rope skipping, dancing) on a force plate. GRF was collected for one step per trial (10 trials) for ambulatory movements and for all landings (10 trials), rope skips and dance procedures. Accelerometer outputs as peak loading (g) per activity were averaged. ANOVA, correlation analyses and Bland-Altman plots were computed to determine validity of accelerometers using GRF. There was a main effect of task with increasing acceleration values in tasks with increasing locomotion speed and landing height (P<0.001). Data from ACT and GEN correlated with GRF (r=0.90 and 0.89, respectively) and between each other (r=0.98), but both accelerometers consistently overestimated GRF. The new generation of accelerometer models that allow raw signal detection are reasonably accurate to measure impact loading of bone in children, although they systematically overestimate GRF.
The purpose of this study was to compare static balance performance and muscle activity during one-leg standing on the dominant and nondominant leg under various sensory conditions with increased levels of task difficulty. Thirty healthy young adults (age: 23 +/- 2 years) performed one-leg standing tests for 30 s under three sensory conditions (ie, eyes open/firm ground; eyes open/foam ground [elastic pad on top of the balance plate]; eyes closed/firm ground). Center of pressure displacements and activity of four lower leg muscles (ie, m. tibialis anterior [TA], m. soleus [SOL], m. gastrocnemius medialis [GAS], m. peroneus longus [PER]) were analyzed. An increase in sensory task difficulty resulted in deteriorated balance performance (P < .001, effect size [ES] = .57-2.54) and increased muscle activity (P < .001, ES = .50-1.11) for all but two muscles (ie, GAS, PER). However, regardless of the sensory condition, one-leg standing on the dominant as compared with the nondominant limb did not produce statistically significant differences in various balance (P > .05, ES = .06-.22) and electromyographic (P > .05, ES = .03-.13) measures. This indicates that the dominant and the nondominant leg can be used interchangeably during static one-leg balance testing in healthy young adults.
Physical Fitness Percentiles of German Children Aged 9-12 Years: Findings from a Longitudinal Study
(2015)
Background
Generating percentile values is helpful for the identification of children with specific fitness characteristics (i. e., low or high fitness level) to set appropriate fitness goals (i. e., fitness/ health promotion and/or long-term youth athlete development). Thus, the aim of this longitudinal study was to assess physical fitness development in healthy children aged 9-12 years and to compute sex-and age-specific percentile values.
Methods
Two-hundred and forty children (88 girls, 152 boys) participated in this study and were tested for their physical fitness. Physical fitness was assessed using the 50-m sprint test (i. e., speed), the 1-kg ball push test, the triple hop test (i. e., upper-and lower-extremity muscular power), the stand-and-reach test (i. e., flexibility), the star run test (i. e., agility), and the 9-min run test (i. e., endurance). Age-and sex-specific percentile values (i. e., P-10 to P-90) were generated using the Lambda, Mu, and Sigma method. Adjusted (for change in body weight, height, and baseline performance) age-and sex-differences as well as the interactions thereof were expressed by calculating effect sizes (Cohen's d).
Results
Significant main effects of Age were detected for all physical fitness tests (d = 0.40-1.34), whereas significant main effects of Sex were found for upper-extremity muscular power (d = 0.55), flexibility (d = 0.81), agility (d = 0.44), and endurance (d = 0.32) only. Further, significant Sex by Age interactions were observed for upper-extremity muscular power (d = 0.36), flexibility (d = 0.61), and agility (d = 0.27) in favor of girls. Both, linear and curvilinear shaped curves were found for percentile values across the fitness tests. Accelerated (curvilinear) improvements were observed for upper-extremity muscular power (boys: 10-11 yrs; girls: 9-11 yrs), agility (boys: 9-10 yrs; girls: 9-11 yrs), and endurance (boys: 9-10 yrs; girls: 9-10 yrs). Tabulated percentiles for the 9-min run test indicated that running distances between 1,407-1,507 m, 1,479-1,597 m, 1,423-1,654 m, and 1,433-1,666 m in 9-to 12-year-old boys and 1,262-1,362 m, 1,329-1,434 m, 1,392-1,501 m, and 1,415-1,526 m in 9-to 12-year-old girls correspond to a "medium" fitness level (i. e., P-40 to P-60) in this population.
Conclusions
The observed differences in physical fitness development between boys and girls illustrate that age- and sex-specific maturational processes might have an impact on the fitness status of healthy children. Our statistical analyses revealed linear (e. g., lower-extremity muscular power) and curvilinear (e. g., agility) models of fitness improvement with age which is indicative of timed and capacity-specific fitness development pattern during childhood. Lastly, the provided age-and sex-specific percentile values can be used by coaches for talent identification and by teachers for rating/ grading of children's motor performance.
The term "bilateral deficit" (BLD) has been used to describe a reduction in performance during bilateral contractions when compared to the sum of identical unilateral contractions. In old age, maximal isometric force production (MIF) decreases and BLD increases indicating the need for training interventions to mitigate this impact in seniors. In a cross-sectional approach, we examined age-related differences in MIF and BLD in young (age: 20-30 years) and old adults (age: > 65 years). In addition, a randomized-controlled trial was conducted to investigate training-specific effects of resistance vs. balance training on MIF and BLD of the leg extensors in old adults. Subjects were randomly assigned to resistance training (n = 19), balance training (n = 14), or a control group (n = 20). Bilateral heavy-resistance training for the lower extremities was performed for 13 weeks (3 x /week) at 80% of the one repetition maximum. Balance training was conducted using predominately unilateral exercises on wobble boards, soft mats, and uneven surfaces for the same duration. Pre-and post-tests included uni-and bilateral measurements of maximal isometric leg extension force. At baseline, young subjects outperformed older adults in uni-and bilateral MIF (all p < .001; d = 2.61-3.37) and in measures of BLD (p < .001; d = 2.04). We also found significant increases in uni-and bilateral MIF after resistance training (all p < .001, d = 1.8-5.7) and balance training (all p < .05, d = 1.3-3.2). In addition, BLD decreased following resistance (p < .001, d = 3.4) and balance training (p < .001, d = 2.6). It can be concluded that both training regimens resulted in increased MIF and decreased BLD of the leg extensors (HRT-group more than BAL-group), almost reaching the levels of young adults.
The purpose of this study was to investigate the effects of back extensor fatigue on performance measures and electromyographic (EMG) activity of leg and trunk muscles during jumping on stable and unstable surfaces.
Before and after a modified Biering-Sorensen fatigue protocol for the back extensors, countermovement (CMJ) and lateral jumps (LJ) were performed on a force plate under stable and unstable (balance pad on the force plate) conditions. Performance measures for LJ (contact time) and CMJ height and leg and trunk muscles EMG activity were tested in 14 male experienced jumpers during 2 time intervals for CMJ (braking phase, push-off phase) and 5 intervals for LJ (-30 to 0, 0-30, 30-60, 60-90, and 90-120 ms) in non-fatigued and fatigued conditions.
A significant main effect of test (fatigue) (p = 0.007, f = 0.57) was observed for CMJ height. EMG analysis showed a significant fatigue-induced decrease in biceps femoris and gastrocnemius activity with CMJ (p = 0.008, f = 0.58 andp = 0.04, f = 0.422, respectively). LJ contact time was not affected by fatigue or surface interaction. EMG activity was significantly lower in the tibialis anterior with LJ following fatigue (p = 0.05, f = 0.405). A test x surface (p = 0.04, f = 0.438) interaction revealed that the non-fatigued unstable CMJ gastrocnemius EMG activity was lower than the non-fatigued stable condition during the onset-of-force phase.
The findings revealed that fatiguing the trunk negatively impacts CMJ height and muscle activity during the performance of CMJs. However, skilled jumpers are not additionally affected by a moderately unstable surface as compared to a stable surface.
This study investigated sex-specific effects of surface instability on kinetics and lower extremity kinematics during drop jumping and landing. Ground reaction forces as well as knee valgus and flexion angles were tested in 14 males (age: 23 +/- 2 years) and 14 females (age: 24 +/- 3 years) when jumping and landing on stable and unstable surfaces. Jump height was found to be significantly lower (9 %, p < 0.001) when drop jumps were performed on unstable vs. stable surface. Significantly higher peak ground reaction forces were observed when jumping was performed on unstable vs. stable surfaces (5 %, p = 0.022). Regarding frontal plane kinematics during jumping and landing, knee valgus angles were higher on unstable compared to stable surfaces (1932 %, p < 0.05). Additionally, at the onset of ground contact during landings, females showed higher knee valgus angles than males (222 %, p = 0.027). Sagittal plane kinematics indicated significantly smaller knee flexion angles (6-35 %, p < 0.05) when jumping and landing on unstable vs. stable surfaces. During drop jumps and landings, women showed smaller knee flexion angles at ground contact compared to men (27-33 %, p < 0.05). These findings imply that knee motion strategies were modified by surface instability and sex during drop jumps and landings.