During knee rehabilitation, squats are a commonly used closed kinetic chain exercise. We have been unable to locate data reporting electromyographic (EMG) activity of lower extremity musculature during maximal effort squats and the contribution of gastrocnemius and gluteus maximus muscles. Therefore, the purposes of this study were (a) to quantify EMG activity of selected lower extremity muscles during a maximal isometric squat and during a maximal voluntary isometric contraction (MVIC), and (b) to determine ratios between the vastus medialis oblique (VMO) and vastus lateralis (VL) during maximal isometric squat and MVIC testing. Twenty-three subjects participated in a single testing session. Results are as follows: intraclass correlations for MVIC testing and squat testing ranged from .60 to .80 and .70 to .90, respectively. Percentage MVIC during the squat was as follows: rectus femoris 40 ± 30%, VMO 90 ± 70%, VL 70 ±40%, hamstrings 10 ± 10%, gluteus maximus 20 ± 10%, and gastrocnemius 30 ± 20%. No statistical difference existed in VMO:VL ratios during MVIC or squat testing. We conclude that large variations in muscle recruitment patterns occur between individuals during isometric squats.
Search Results
EMG Activity of Six Muscles and VMO:VL Ratio Determination during a Maximal Squat Exercise
Peter A. Schaub and Teddy W. Worrell
Validity of an Inexpensive Hanging Scale During Isometric Shoulder Movements
Matheus Lima Oliveira, Isabela Christina Ferreira, Kariny Realino Ferreira, Gabriela Silveira-Nunes, Michelle Almeida Barbosa, and Alexandre Carvalho Barbosa
. SEM was also calculated to provide an estimate of measurement error. Linear regression estimated the coefficient of correlation ( R ) and the adjusted coefficient of determination ( R 2 ). Bland–Altman method estimated the measurement bias, with lower and upper limits of agreement between results. All
Central Activation Ratio Is a Reliable Measure for Gluteal Neuromuscular Function
Daniel Gilfeather, Grant Norte, Christopher D. Ingersoll, and Neal R. Glaviano
calculate the coefficient of determination. 23 The first relationship was comparing the graded stimuli at rest with the torque output to evaluate complete gluteal motor unit recruitment. The second relationship was comparing the relationship between the maximal stimulus during the progressive contractions
Relationship Between 3 Single-Leg Functional Performance Tests for Netball Noncontact Knee Injury Prevention Screening in Uninjured Female Adult Players
Nicholas C. Clark and Elaine M. Mullally
inspection and Pearson correlation ( r ). Correlations were defined as moderate to strong (.50–.75) and strong to very strong (.75–1.00). 51 The proportion (in percentage) of variance shared between tests was assessed with the coefficient of determination ( r 2 ). 23 An r 2 ≥ .60 was employed as a
Comparison of Weight-Bearing and Non-Weight-Bearing Conditions on Knee Joint Reposition Sense
Michael J. Higgins and David H. Perrin
In this study, joint reposition sense of the knee in a non-weight-bearing (NWB) state and that in a weight-bearing (WB) state were compared, and it was determined whether a significant relationship existed between knee displacement (KD) and joint reposition sense. The dominant knees of 8 male and 12 female subjects (age 19–26 years, M ± SD = 21.5 ± 2.06) who had no previous history of knee dysfunction were tested for accuracy of angular reproduction in the WB and NWB states. There was a significant difference in the accuracy of angular repositioning between the two conditions, with the WB test having less deviation from the predetermined angle. There was a weak relationship between KD and the ability to reproduce specific angles of the knee. These results suggest that the WB or closed chain state of the knee was more accurate in the determination of joint position sense than the NWB or open chain condition.
The Relationship of Ankle Temperature during Cooling and Rewarming to the Human Soleus H Reflex
B. Andrew Krause., J. Ty Hopkins, Christopher D. Ingersoll, Mitchell L. Cordova, and Jeffrey E. Edwards
Objective:
Correlate skin temperature and motoneuron-pool recruitment during cooling and rewarming.
Design:
Within-subjects, correlational analysis. H reflex was correlated to ankle-skin temperature over time using a Pearson product-moment correlation coefficient and a coefficient of determination (R2).
Subjects:
Ten healthy, physically active college students.
Measurements:
Soleus H reflex and ankle-skin interface temperature were measured during ice application and rewarming. Electrical stimulation was delivered to produce 75% of each subject's maximum H reflex.
Results:
Ankle cooling (r = −.95, P < .05) exhibited a strong inverse relationship with soleus H reflex. A positive correlation was observed between rewarming (r = .74, P < .05) and soleus H reflex.
Conclusions:
Temperature accounts for nearly 90% (R2 = .90) of the variability in the soleus H reflex during cooling and 55% (R2 = .55) during rewarming, suggesting that more motoneurons are recruited as temperature decreases. These interactions appear to involve both local and central nervous system functions.
Return to Sport after Serious Injury: A Retrospective Examination of Motivation and Psychological Outcomes
Leslie Podlog and Robert C. Eklund
Context:
It is argued in self-determination theory that the motivation underlying behavior has implications for health and well-being independent of the behavior itself.
Objective:
To examine associations between athlete motivations for returning to sport after injury and perceived psychological return-to-sport outcomes.
Design:
A correlational survey design was employed to obtain data in Canada, Australia, and England.
Participants:
Elite and subelite athletes (N = 180) with injuries requiring a minimum 2-month absence from sport participation.
Main Outcome Measures:
Participants completed an inventory measuring perceptions of motivation to return to sport from a serious injury and psychological return-to-sport outcomes.
Results:
Correlational analyses revealed that intrinsic motivations for returning to competition were associated with a positive renewed perspective on sport participation. Conversely, extrinsic motivations for returning to sport were associated with increased worry and concern.
Conclusions:
The motivation underlying return to sport might play an important role in return-to-sport perceptions among elite and subelite athletes.
Effect of a High-Intensity Intermittent-Exercise Protocol on Neurocognitive Function in Healthy Adults: Implications for Return-to-Play Management After Sport-Related Concussion
Enda F. Whyte, Nicola Gibbons, Grainne Kerr, and Kieran A. Moran
Context: Determination of return to play (RTP) after sport-related concussion (SRC) is critical given the potential consequences of premature RTP. Current RTP guidelines may not identify persistent exercise-induced neurocognitive deficits in asymptomatic athletes after SRC. Therefore, postexercise neurocognitive testing has been recommended to further inform RTP determination. To implement this recommendation, the effect of exercise on neurocognitive function in healthy athletes should be understood. Objective: To examine the acute effects of a high-intensity intermittent-exercise protocol (HIIP) on neurocognitive function assessed by the Symbol Digits Modality Test (SDMT) and Stroop Interference Test. Design: Cohort study. Setting: University laboratory. Participants 40 healthy male athletes (age 21.25 ± 1.29 y, education 16.95 ± 1.37 y). Intervention: Each participant completed the SDMT and Stroop Interference Test at baseline and after random allocation to a condition (HIIP vs control). A mixed between-within-subjects ANOVA assessed time- (pre- vs postcondition) -by-condition interaction effects. Main Outcome Measures: SDMT and Stroop Interference Test scores. Results: There was a significant time-by-condition interaction effect (P < .001, η 2 = .364) for the Stroop Interference Test scores, indicating that the HIIP group scored significantly lower (56.05 ± 9.34) postcondition than the control group (66.39 ± 19.6). There was no significant time-by-condition effect (P = .997, η 2 < .001) for the SDMT, indicating that there was no difference between SDMT scores for the HIIP and control groups (59.95 ± 10.7 vs 58.56 ± 14.02). Conclusions: In healthy athletes, the HIIP results in a reduction in neurocognitive function as assessed by the Stroop Interference Test, with no effect on function as assessed by the SDMT. Testing should also be considered after high-intensity exercise in determining RTP decisions for athletes after SRC in conjunction with the existing recommended RTP protocol. These results may provide an initial reference point for future research investigating the effects of an HIIP on the neurocognitive function of athletes recovering from SRC.
Test–Retest of a Novel Wii Board–Based Device to Assess Eccentric Knee Flexor Strength During the Nordic Hamstring Exercise
Maria de Cássia Macedo, Matheus Almeida Souza, Geyson de Lima Batista, Michelle Almeida Barbosa, and Alexandre Carvalho Barbosa
, Kiel University, Germany) considering a coefficient of determination of 0.577 obtained from a previous similar study 16 using the bilateral testing peak force as the main variable, with an alpha of 5% and a sampling power (1−β) of 95%. A sample size of 12 subjects was returned with an actual power of
Role of Thigh Muscle Strength and Joint Kinematics in Dynamic Stability: Implications for Y-Balance Test Performance
Jeffrey A. Turner, Matthew L. Hartshorne, and Darin A. Padua
in an iterative fashion, 1 variable at a time was removed if their P value was >.1. 32 The final model was selected by comparing the adjusted R 2 and Akaike information criteria (AIC) between all stepwise models. 32 Each directional reach’s final model’s coefficient of determination ( R 2
