Purpose: The current investigation aimed to investigate the longitudinal association between physical fitness and academic performance over 3 years in adolescents. A secondary aim was to determine to what extent waist circumference mediated the association between physical fitness and academic performance. Methods: For the current study, 1020 students from first grade [mean age: 7.87 (0.34) y] to fifth grade [mean age: 11.87 (0.37) y] were monitored annually for 3 years (2010–2013). Physical fitness was assessed using the Andersen test, 5 × 5-m shuttle run, jump height, and grip strength tests and by constructing a composite score combining all 4 fitness tests. Academic performance was assessed by national standardized tests in Danish language and math. Generalized structural equation modeling was used to evaluate the relationships between these variables. Results: The Andersen test (standardized β = 0.15 SD), shuttle run (β = −0.18 SD), jump height (β = 0.10 SD), and the fitness composite score (β = 0.23 SD) were positively associated with academic performance over 3 years. In addition, waist circumference partially mediated the association between physical fitness and academic performance. Conclusion: Thus, physical fitness abilities should be stimulated during childhood and early adolescence because of their positive association with academic performance.
Rodrigo Antunes Lima, Lisbeth Runge Larsen, Anna Bugge and Lars Bo Andersen
Stefan C. Garcia, Jeffrey J. Dueweke and Christopher L. Mendias
Context: Manual isometric muscle testing is a common clinical technique used to assess muscle strength. To provide the most accurate data for the test, the muscle being assessed should be at a length in which it produces maximum force. However, there is tremendous variability in the recommended positions and joint angles used to conduct these tests, with few apparent objective data used to position the joint such that muscle-force production is greatest. Objective: To use validated anatomically and biomechanically based musculoskeletal models to identify the optimal joint positions in which to perform manual isometric testing. Design: In silico analysis. Main outcome measure: The joint position which produces maximum muscle force for 49 major limb and trunk muscles. Results: The optimal joint position for performing a manual isometric test was determined. Conclusion: Using objective anatomical models that take into account the force-length properties of muscles, the authors identified joint positions in which net muscle-force production was predicted to be maximal. This data can help health care providers to better assess muscle function when manual isometric strength tests are performed.
Kristian M. O’Connor, Carl Johnson and Lauren C. Benson
The function of the hamstrings in protecting the ACL is not fully understood. The purpose of this study was to determine how landing knee mechanics were affected by hamstrings fatigue, analyzed with principal components analysis (PCA). Knee joint mechanics were collected during single-leg stride landings that were followed by lateral and vertical jumps. An isokinetic fatigue protocol was employed to reduce hamstrings strength by 75% at the cessation of the exercise protocol. On the landing test day, participants performed the stride landing maneuvers before and after the fatigue protocol. PCA was performed on the landing knee joint angle, moment, and power waveforms, and MANOVAs were conducted on the retained PCs of each waveform (P < .05). On the strength test day, hamstrings strength recovery was assessed with an identical fatigue protocol followed by strength assessment ~75 s after the cessation of exercise. Pre- and postexercise hamstrings strength on this day was assessed with a dependent t test (P < .05). The hamstrings strength remained significantly reduced by ~8% postexercise (75 s). For stride landings followed by vertical jumps, there were significantly reduced knee flexion angles, extensor moments, and energy absorption. This was indicative of a stiffer landing strategy postfatigue, which has been associated with increased ACL loading.
Joe Nocera, Mack Rubley, William Holcomb and Mark Guadagnoli
There is limited information on the effects of throwing on shoulder proprioception and strength.
Examine shoulder proprioception and strength following throwing.
2x3 mixed-subject design.
Research laboratory and outdoor facility.
23 male college students (age = 22 ± 2.9yr, ht = 178 ± 11.3cm, wt = 72 ± 7.7kg, 22 right-handed 1 left-handed).
Subjects were pretested for proprioception, measured by active reproduction of passive positioning (ARPP). Strength was quantified using 1RM and an average peak torque at 120º/sec for internal and external shoulder rotation. Following pretesting, subjects (excluding control) completed 75 throws at 75% maximum immediately followed by posttesting.
Main Outcome Measures:
Pre and post ARPP absolute error and strength changes.
Significant difference in the pre and posttest ARPP values for throwing groups but no difference for the control group. There was no significant difference from pre to post on the strength tests for any groups.
Results indicate that repetitive throwing affects proprioception while not affecting strength.
Christopher Thomas, Paul Comfort, Paul A. Jones and Thomas Dos’Santos
To investigate the relationships between maximal isometric strength, vertical jump (VJ), sprint speed, and change-of-direction speed (CoDS) in academy netball players and determine whether players who have high performance in isometric strength testing would demonstrate superior performance in VJ, sprint speed, and CoDS measures.
Twenty-six young female netball players (age 16.1 ± 1.2 y, height 173.9 ± 5.7 cm, body mass 66.0 ± 7.2 kg) from a regional netball academy performed isometric midthigh pull (IMTP), squat jumps (SJs), countermovement jumps (CMJs), 10-m sprints, and CoDS (505).
IMTP measures displayed moderate to strong correlations with sprint and CoDS performance (r = –.41 to –.66). The VJs, which included SJs and CMJs, demonstrated strong correlations with 10-m sprint times (r = –.60 to –.65; P < .01) and CoDS (r = –.60 to –.71; P = .01). Stronger players displayed significantly faster sprint (ES = 1.1–1.2) and CoDS times (ES = 1.2–1.7) and greater VJ height (ES = 0.9–1.0) than weaker players.
The results of this study illustrate the importance of developing high levels of lower-body strength to enhance VJ, sprint, and CoDS performance in youth netball players, with stronger athletes demonstrating superior VJ, sprint, and CoDS performances.
Robert van Cingel, Gertjan Kleinrensink, Rob Stoeckart, Geert Aufdemkampe, Rob de Bie and Harm Kuipers
To determine concentric shoulder external-internal rotator strength, dominant and non-dominant shoulder differences and agonist/antagonist ratios.
A transversal study of isokinetic dynamometry of healthy shoulders, 95% confidence intervals are presented.
35 asymptomatic elite, male volleyball players.
Peak torque normalized for body weight was recorded at 60, 180, and 300°/sec. with a Cybex 6000 dynamometer.
(1) internal rotators were significantly stronger than external rotators of the same shoulder; (2) internal rotators of the dominant arm were significantly stronger than of the non-dominant arm; (3) no difference existed between external rotators of the dominant and the non-dominant arm; (4) external–internal rotator ratios of the dominant arm were significantly lower than of the non-dominant arm; and (5) no differences were found between the ratios of each arm separately.
Data presented are important for interpreting isokinetic shoulder rotator strength tests in elite volleyball players and could be relevant in rehabilitation and prevention of shoulder injuries.
Gregory M. Gutierrez, Catherine Conte and Kristian Lightbourne
Head impacts are common in contact sports, but only recently has there been a rising awareness of the effects of subconcussive impacts in adolescent athletes. A better understanding of how to attenuate head impacts is needed and therefore, this study investigated the relationship between neck strength, impact, and neurocognitive function in an acute bout of soccer heading in a sample of female high school varsity soccer players. Seventeen participants completed the ImPACT neurocognitive test and had their isometric neck strength tested (flexion, extension, and bilateral flexion) before heading drills. Each participant was outfitted with custom headgear with timing switches and a three-dimensional accelerometer affixed to the back of the head, which allowed for measurement of impact during heading. Participants performed a series of 15 directional headers, including 5 forward, 5 left and 5 right headers in a random order, then completed the ImPACT test again. Neurocognitive tests revealed no significant changes following heading. However, there were statistically significant, moderate, negative correlations (r = −0.500:−0.757, p < .05) between neck strength and resultant header acceleration, indicating that those with weaker necks sustained greater impacts. This suggests neck strengthening may be an important component of any head injury prevention/reduction program.
Johanne Desrosiers, François Prince, Annie Rochette and Michel Raîche
The objectives of this study were to standardize measurement procedures and study the test-retest and interrater reliability of the belt-resisted method for measuring the lower extremity isometric strength of three muscle groups. The strength of 33 healthy, elderly, community-dwelling subjects was evaluated with a hand-held dynamometer using the belt-resisted method. Isometric strength testing of three muscle groups (hip flexors, knee extensors, and ankle dorsiflexors) was performed on two separate occasions, I week apart, by the same tester to determine test-retest reliability. The test results of two different examiners testing on different days were used to determine interrater reliability. Test-retest reliability was higher than interrater reliability. Test-retest reliability coefficients of the three muscle groups were high (J9-.95). For interrater reliability, intraclass correlation coefficients varied from .64 to .92. depending on the muscle group and side. For the two kinds of reliability, intraclass correlation coefficients increased from proximal to distal. The method for the hip muscle group should be modified to increase reliability of the measure.
Michael P. Corcoran, Miriam E. Nelson, Jennifer M. Sacheck, Kieran F. Reid, Dylan Kirn, Roger A. Fielding, Kenneth K.H. Chui and Sara C. Folta
This cluster-randomized trial was designed to determine the efficacy of a 6-month exercise-nutritional supplement program (ENP) on physical function and nutritional status for older adults and the feasibility of implementing this program in a senior living setting. Twenty senior-living facilities were randomized to either a 3 day per week group-based ENP led by a trained facility staff member or a health education program (SAP). Participants (N = 121) completed a short physical performance battery, 400-m walk, handgrip strength test, and mini-nutrition assessment. 25-hydroxyvitamin D [25(OH)D], insulin-like growth-factor 1 (IGF-1), and activity level were also measured. The ENP did not significantly improve physical function or nutritional status compared with the SAP. Compared with baseline, participants in the ENP engaged in 39 min less physical activity per week at 6 months. Several facility characteristics hindered implementation of the ENP. This study highlights the complexity of implementing an evidence-based program in a field setting.
Taina Rantanen, Pertti Era, Markku Kauppinen and Eino Heikkinen
This study analyzes the associations of socioeconomic status (SES), health, and physical activity with maximal isometric strength in 75-year-old men (n = 104) and women (n = 191). Maximal isometric strength was measured with dynamometers; the forces were adjusted using body weight. The maximal forces for women varied from 66% (trunk flexion) to 73% (knee extension) of those of the men. SES was not associated with muscle force. For men the trunk forces and elbow flexion force correlated negatively with the number of chronic diseases, index of musculoskeletal pain, and self-rated health. For women all the strength test results correlated with self-rated health; the other health indicators showed significant correlation with trunk extension force only. For both sexes the physically more active exhibited greater strength. The index of musculoskeletal symptoms explained the variance on trunk force factor in both sexes. It was concluded that a higher level of everyday physical activity and good values in the state-of-health indicators were the most important variables explaining greater strength among the elderly.