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The aim of this study was to explore the relationship between muscle fiber conduction velocity (MFCV), fiber type composition, and power performance in participants with different training background.Thirty-eight young males with different training background participated: sedentary (n = 10), endurance runners (n = 9), power trained (n = 10), and strength trained (n = 9). They performed maximal countermovement jumps (CMJ) and maximal isometric leg press for the measurement of the rate of force development (RFD). Resting vastus lateralis MFCV was measured with intramuscular microelectrodes on a different occasion, whereas muscle fiber type and cross-sectional area (CSA) of vastus lateralis were evaluated through muscle biopsies 1wk later.MFCV, CMJ power, RFD, and % CSA of type II and type IIx fibers were higher for the power-trained group (P0.001). No difference was found between sedentary participants and endurance runners in these variables, but both of these groups performed worse than strength/power participants. Close correlations were found between MFCV and fiber CSA as well as the % CSA of all fiber types as well as with RFD and CMJ power (r = 0.712-0.943, P0.005). Partial correlations revealed that the % CSA of IIx fibers dictates a large part of the correlation between MFCV and RFD, power performance. Significant models for the prediction of the % CSA of type IIa and type II as well as the CSA of all muscle fibers based upon MFCV, RFD, and CMJ were revealed (P = 0.000).MFCV is closely associated with muscle fiber % CSA. RFD and jumping power are associated with the propagation of the action potentials along the muscle fibers. This link is regulated by the size and the distribution of type II, and especially type IIx muscle fibers.

Incremental cardiopulmonary exercise test with gas exchange measurement is the gold standard for the identification of the ventilatory compensation point (VCP). It has previously been demonstrated that the change in the slope of increment of minute ventilation over HR (?V?E/?HR) can be used alternatively to the ventilatory equivalent for CO2 (V?E/V?CO2) method for detection of VCP in healthy subjects undergoing cycle ergometer (C) incremental exercise. The same evaluation during treadmill (T) incremental exercise and comparison between C and T have not yet been performed. Purpose: We analyzed, during both C and T incremental exercises, the V?E/HR and the respiratory rate (RR)/HR relationships, expressed either as slope or as an absolute value. We hypothesized that changes in the slope of increment of the two relationships could represent a reliable method for VCP detection, regardless of exercise mode and protocol. Methods: Fourteen healthy male subjects (age = 31 ± 7 yr (mean ± SD)) underwent two T incremental exercises�fast (FT) and slow (ST) protocols (8 km·h-1, 2% (FT) and 1% (ST) grade per minute)�and one C incremental exercise (30 W·min-1). O2 uptake (V?O2), V?CO2, V?E, HR, and RR were measured breath by breath. Results: A good between-method agreement in the detection of VCP by the ?V?E/?V?CO2, ?V?E/?HR, and the ?RR/?HR slope changes was found in both T protocols and C. No differences (C vs T and FT vs ST) were found in the slope of the ?V?E/?HR and ?RR/?HR relationships after the VCP and in the V?E/HR and RR/HR absolute values at VCP. Conclusions: In healthy young males, the ?V?E/?HR and ?RR/?HR relationships during T and C incremental exercises can be reliably used to detect the VCP as an alternative to the ventilatory equivalent method.

Purpose: It has been generally assumed that muscle volume is not a limiting factor of balance for young populations. To verify this assumption, this study investigated the relationship between postural stability and muscle volume of the plantar flexors, which have been regarded as the major agonist muscles for postural control, of healthy young male individuals. Methods: Forty-five healthy young males were requested to maintain quiet standing on a force platform for 60 s in eyes-open and eyes-closed conditions. Various time and frequency domain measures of the center of pressure were calculated. Muscle volume of the plantar flexors was estimated from muscle thickness in the lateral gastrocnemius and soleus muscles measured by ultrasonography and was divided by body mass to yield the normalized muscle volume. Results: Many time domain center of pressure measures such as mean distance, root mean square, and mean velocity were negatively correlated to normalized muscle volume (P < 0.05). Conclusions: It is suggested that, even among the young males, the muscle volume of their plantar flexors can act as a limiting factor for postural stability

Recent innovations in physical activity (PA) assessment have made it possible to assess the walking behaviors of a wide variety of populations. Objective measurement methods (e.g., pedometers, accelerometers) have been widely used to assess walking and other prevalent types of PA. Questionnaires suitable for international populations (e.g., the International Physical Activity Questionnaire and the Global Physical Activity Questionnaire) and measurement techniques for the assessment of gait patterns in disabled populations allow for the study of walking and its health benefits among many populations. Results of studies using the aforementioned techniques indicate that children are more active than adolescents and adolescents are more active than adults. Males, particularly young males, are typically more active than females. The benefits associated with regular participation in PA for youth and walking for older adults have been well documented, although improvements in the assessments of physical, cognitive, and psychosocial parameters must be made if we are to fully understand the benefits of walking for people of all ages. Most youth meet appropriate age-related PA activity recommendations, but adults, particularly older adults and adults with disabilities, are less likely to meet PA levels necessary for the accrual of health benefits. International studies indicate variation in walking by culture. It is clear, however, that walking is a prevalent form of PA across countries and a movement form that has great potential in global PA promotion. Continued development of measurement techniques that allow for the study of individualized gait patterns will help us add to the already rich body of knowledge on chronically disabled populations and allow for individual prescriptions for these populations.