Higbie, Elizabeth J., Kirk J. Cureton, Gordon L. Warren III, and Barry M. Prior. Effects of concentric and eccentric training on muscle strength, cross-sectional area, and neural activation. J. Appl. Physiol. 81(5): 2173-2181, 1996.-We compared the effects of concentric (Con) and eccentric (Ecc) isokinetic training on quadriceps muscle strength, cross-sectional area, and neural activation. Women (age 20.0 6 0.5 yr) randomly assigned to Con training (CTG; n 5 16), Ecc training (ETG; n 5 19), and control (CG; n 5 19) groups were tested before and after 10 wk of unilateral Con or Ecc knee-extension training. Average torque measured during Con and Ecc maximal voluntary knee extensions increased 18.4 and 12.8% for CTG, 6.8 and 36.2% for ETG, and 4.7 and 21.7% for CG, respectively. Increases by CTG and ETG were greater than for CG (P , 0.05). For CTG, the increase was greater when measured with Con than with Ecc testing. For ETG, the increase was greater when measured with Ecc than with Con testing. The increase by ETG with Ecc testing was greater than the increase by CTG with Con testing. Corresponding changes in the integrated voltage from an electromyogram measured during strength testing were 21.7 and 20.0% for CTG, 7.1 and 16.7% for ETG, and 28.0 and 29.1% for CG. Quadriceps cross-sectional area measured by magnetic resonance imaging (sum of 7 slices) increased more in ETG (6.6%) than in CTG (5.0%) (P , 0.05). We conclude that Ecc is more effective than Con isokinetic training for developing strength in Ecc isokinetic muscle actions and that Con is more effective than Ecc isokinetic training for developing strength in Con isokinetic muscle actions. Gains in strength consequent to Con and Ecc training are highly dependent on the muscle action used for training and testing. Muscle hypertrophy and neural adaptations contribute to strength increases consequent to both Con and Ecc training. electromyography; isokinetic muscle actions; muscle hypertrophy; training specificity; quadriceps muscle; women IT IS WELL ESTABLISHED that the primary stimulus for increasing the maximal force that can be exerted in a given movement (strength) is the repeated development of force by skeletal muscles at levels above those encountered in everyday activities (17). The increase in strength is proportional to the amount of overload as measured by the relative force developed and the number of muscle actions performed during conditioning (17). Because greater maximum force can be developed during maximal eccentric (Ecc) muscle actions than during concentric (Con) or isometric muscle actions (6), it has been suggested that heavy-resistance training using Ecc muscle actions may be more effective than training using Con or isometric muscle actions in increasing strength (3,7,13).Studies comparing the effectiveness of Ecc and Con muscle actions in increasing muscular strength have been equivocal (3, 4, 7-9, 18, 20-22, 24, 26, 40, 43). Different training protocols and methods of assessment have contributed to different outcomes. In studies ...

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Study Design: A withinsubjects repeated measures design.Objectives To determine differences in the amount of vertical opening of the mandible among 3 different head positions. Background: Results from several studies have suggested that the position of the head and neck may affect temporomandibular joint function. Presently no standardized position of the head and neck has been recommended for measuring vertical opening of the mandible. Methods and Measures: Twenty males and 20 females (32.9 2 8.3 years) participated in the study. We obtained 3 measurements of vertical mandibular opening using a millimeter ruler on each subject in the forward, neutral, and retracted head positions. Results: A 1 -way repeated measures analysis of variance followed by pairwise comparisons indicated that the vertical mandibular opening was significantly greater in the forward head position (44 2 5.3 mm) than in the neutral head position (41.5 2 4.8 mm) and in the retracted head position (36.2 2 4.5 mm). In addition, vertical mandibular opening was significantly greater in the neutral head position than in the retracted head position. Interclass correlation coefficients for the 3 head positions ranged from 0.90 to 0.97 for intrarater, interrater, and day-to-day reliability. Conclusions: Head position is an important factor in determining the amount of vertical mandibular opening in healthy adults. ) Orthop Sportr Phys Ther 1999;29:127-130.

Study Design: Counterbalanced experimental design study comparing a group of subjects with greater than or equal to 7°of forefoot varus (MFV) to a group with less than 7°of forefoot varus (LFV). Objectives: To investigate the effect of forefoot varus on single-limb stance postural stability (PS). Background: Impaired PS has been implicated as a potential risk factor for sustaining acute foot and ankle injuries. The identification of variables that deleteriously affect PS may be important in the prevention of future injuries. Methods and Measures: Postural stability of the MFV group (n = 20) and the LFV group (n = 12) was assessed during right and left single-limb stance and eyes-open and eyes-closed conditions. Standard deviations of the x-axis and y-axis ground reaction forces measured via a force platform were used to represent anteroposterior (AP) and mediolateral (ML) PS, respectively. The mean of 3 successful 5-second trials of each testing condition was calculated and used for subsequent data analysis using 3-way mixed-model ANOVAs with 1 between-subject and 2 within-subject factors. Results: The AP PS scores of the MFV group were significantly greater than those of the LFV group (PϽ.05). ML PS scores, although higher in the MFV group, were not significantly different from those of the LFV group. Both groups had significantly greater AP and ML PS scores during the eyes-closed versus the eyes-open condition (PϽ.05). Conclusions:The results suggest that the presence of greater than or equal to 7°of forefoot varus may significantly impair AP PS. The decreased stability associated with increased forefoot varus may be due to decreased joint congruity and consequently an increased reliance on soft tissue structures for stability.