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  • Author: Jose Luis Felipe x
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Enrique Colino, Jorge Garcia-Unanue, Leonor Gallardo, Carl Foster, Alejandro Lucia and Jose Luis Felipe

Purpose: To characterize, for the first time, the mechanical properties of treadmill surfaces along with a practical interpretation of their influence on physiological and perceived demands during endurance running compared with other widely used surfaces such as asphalt and tartan tracks. Methods: Ten experienced male endurance runners performed a 40-minute running bout at a preferred constant speed on 3 different surfaces (after a randomized, counterbalanced order with a 7-d interval between trials): asphalt, tartan, or treadmill. Shock absorption, vertical deformation, and energy restitution were measured for the 3 surfaces. Intensity (based on heart rate data) and rating of perceived exertion were monitored. Results: The values of shock absorption averaged 0.0% (asphalt), 37.4% (tartan), and 71.3% (treadmill), while those of vertical deformation and energy restitution averaged 0.3, 2.2, and 6.5 mm and 90.8%, 62.6%, and 37.0%, respectively. Running intensity (as determined by heart rate data) was higher overall on the treadmill than tartan but not asphalt running. Except for the first 10 minutes, all mean rating of perceived exertion values were significantly higher in asphalt and treadmill than in tartan. No significant differences were identified between treadmill and asphalt. Conclusions: The considerably higher shock absorption of the treadmill than the tartan surface leads to a reduction in the amount of energy returned to the athlete, which in turn increases physiological stress and rating of perceived exertion during endurance running.

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Jorge López-Fernández, Javier Sánchez-Sánchez, Jorge García-Unanue, José Luis Felipe, Enrique Colino and Leonor Gallardo

Purpose: Recent studies have shown that soccer players’ responses are similar on natural grass (NG) and artificial turf (AT), but they did not control the mechanical properties of these surfaces. This work aimed to analyze the influence of the game surface on amateur soccer players’ physical and physiological responses using a soccer simulation protocol. Methods: A total of 16 amateur players performed 3 bouts of the soccer simulation protocol on AT, and, on another day, 3 bouts on NG. The mechanical properties of both surfaces were recorded. The order of surfaces was randomly established for each participant. Physiological responses of players were assessed before and after the 6-repeated-sprints test existing at the midpoint of each bout. Fatigue (% best; % diff) and general variables (total time; best time, mean time; maximum speed) for both the repeated sprint test (RST) and the agility tests (nonlinear actions at maximum speed) incorporated into the soccer simulation protocol were also analyzed. Results: The 2 surfaces displayed different mechanical properties. Physical responses were found similar for both surfaces (P > .05) before and after the RST. There were no surface differences in sprint times or fatigue variables for the RST (P > .05). The agility test was faster on AT than on NG in bout 1 (average speed [+1.17 km/h;P = .037]; agility test cut time [−0.31 s; P = .027] and best time [−0.52 s; P = .042]). Conclusions: The differences in the mechanical properties of the 2 surfaces are not sufficient to cause differences in the physiological and physical responses of soccer players, although they may affect turns and cuts.

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José Moncada-Jiménez, Eric P. Plaisance, Michael L. Mestek, Lance Ratcliff, Felipe Araya-Ramírez, James K. Taylor, Peter W. Grandjean and Luis F. AragónVargas

Purpose:

This study investigated the effects of short-term dietary changes on metabolism and duathlon performance.

Methods:

Eleven men underwent a high-fat (HF; >65% fat from energy) or a high-carbohydrate (CHO; HC) diet (>60% CHO from energy). Energy intake was individualized, and commercially available foods were prepared and packaged for each participant 48 hr before they completed a laboratory-based duathlon (5-km run, 30 km cycling, and 10-km run). Blood samples were obtained before, immediately after, and 1 and 2 hr after the duathlon for determination of glucose, insulin, and glucagon. Oxygen consumption, ratings of perceived exertion (RPE), and respiratory-exchange ratio were assessed, and fat and CHO oxidation were estimated before, during, and after the duathlon.

Results:

Dietary records indicated a significant difference in fat content ingested before the duathlons (p < .05). Time to complete the duathlon did not differ between the HC- and the HF-diet trials. CHO-oxidation rate was higher during the HC-diet trial than during the HF-diet trial (p = .006). Fat-oxidation rates were higher in the HF-diet trial than in the HC-diet trial (p = .001). No differences in RPE were found between dietary trials. Blood glucose concentration was higher immediately after the duathlon in the HC-diet trial than in the HF-diet trial and remained higher 1 and 2 hr after the duathlon (p < .05).

Conclusion:

Duathlon performance was not altered by short-term changes in dietary fat or CHO composition despite higher blood glucose concentrations under the HC condition.