Search

Purpose: We aimed to identify the underpinning physiological and speed/mechanical determinants of different types of 800-m running time trials (i.e. with a positive or negative pacing strategy) and key components within each 800-m time trial (i.e. first and final 200 m). Methods: Twenty trained male 800-m runners (800-m personal best time (min:s): 1:55.10 +/- 0:04.44) completed a maximal 800-m time trial (800MAX) and one pacing trial, whereby runners were paced for the first lap, and speed was reduced by 7.5% (800PACE) relative to 800MAX, whereas the last lap was completed in the fastest time possible. Anaerobic speed reserve, running economy, the velocity corresponding with V[spacing dot above]O2peak (VV[spacing dot above]O2peak), maximal sprint speed (MAXSS), maximal accumulated oxygen deficit, and sprint force-velocity-power profiles were derived from laboratory and field testing. Carnosine content was quantified by proton magnetic resonance spectroscopy in the gastrocnemius and soleus and expressed as a carnosine aggregate Z (CAZ) score to estimate muscle typology. Data were analyzed using multiple stepwise regression analysis. Results : MAXSS and vV[spacing dot above]O2peak largely explained the variation in 800MAX time (r 2 = 0.570; P = 0.020), whereas MAXSS was the best explanatory variable for the first 200-m time in 800MAX (adjusted r 2 = 0.661, P < 0.001). Runners with a higher CAZ score (i.e. higher estimated percentage of type II fibers) reduced their last lap time to a greater extent in 800PACE relative to 800MAX (adjusted r 2 = 0.413, P < 0.001), whereas better maintenance of mechanical effectiveness during sprinting, a higher CAZ score and vV[spacing dot above]O2peak was associated with a faster final 200-m time during 800PACE (adjusted r 2 = 0.761, P = 0.001). Conclusions: These findings highlight that diversity in the physiological and speed/mechanical characteristics of male middle-distance runners may be associated with their suitability for different 800-m racing strategies to have the best chance of winning. [ABSTRACT FROM AUTHOR]

Purpose: This study aimed to identify the relationships between lower limb muscle characteristics and mechanical variables derived from the vertical (jumping) and horizontal (sprinting) force-- velocity--power (FVP) profiles. Methods: Nineteen subelite male rugby league players performed a series of squat jumps and linear 30-m sprints to derive the vertical and horizontal FVP profiles, respectively. The theoretical maximal force (F0), velocity (V0), and power (Pmax) were derived from both the vertical (i.e., vF0, vV0, and vPmax) and the horizontal (i.e., hF0, hV0, and hPmax) FVP profiles. Vastus lateralis (VL), biceps femoris long head, and gastrocnemius medialis (GM) and lateralis muscle fascicle length, pennation angle, and thickness were measured using B-mode ultrasonography.Magnetic resonance imaging was used to calculate volumes of major lower limb muscles, whereas proton magnetic resonance spectroscopy was used to quantify the carnosine content of the GM to estimate muscle fiber typology. Results: Variation in vPmax was best explained by GM muscle fiber typology (i.e., greater estimated proportion of Type II fibers) and VL volume (adjusted r² = 0.440, P = 0.006), whereas adductor and vastus medialis volume and GM muscle fiber typology explained the most variation in hPmax (adjusted r² = 0.634, P = 0.032). Rectus femoris and VL volume explained variation in vF0 (r² = 0.430, P = 0.008), whereas adductor and vastus medialis volume explained variation in hF0 (r² = 0.432, P = 0.007). Variations in vV0 and hV0 were best explained by GM muscle fiber typology (adjusted r² = 0.580, P < 0.001) and GM muscle fiber typology and biceps femoris short head volume (adjusted r² = 0.590, P < 0.001), respectively. Conclusion: Muscle fiber typology and muscle volume are strong determinants of maximal muscle power in jumping and sprinting by influencing the velocity- and force-oriented mechanical variables. [ABSTRACT FROM AUTHOR]