Combined strength and endurance session order: differences in force production and oxygen uptake.

PURPOSE: To examine acute responses of force production and oxygen uptake to combined strength (S) and endurance-running (E) loading sessions in which the order of exercises is reversed (ES vs SE). METHODS: This crossover study design included recreationally endurance-trained men and women (age 21-45 y; n=12 men, 10 women) who performed ES and SE loadings. Force production of the lower extremities including countermovement-jump height (CMJ) and maximal isometric strength (MVC) was measured pre-, mid-, and post-ES and -SE, and ground-reaction forces, ground-reaction times, and running economy were measured during E. RESULTS: A significant decrease in CMJ was observed after combined ES and SE in men (4.5%±7.0% and 6.6%±7.7%, respectively) but not in women (0.2%±8.5% and 1.4%±7.3% in ES and SE). MVC decreased significantly in both men (20.7%±6.1% ES and 19.3%±9.4% SE) and women (12.4%±9.3% ES and 11.6%±12.0% SE). Stride length decreased significantly in ES and SE men, but not in women. No changes were observed in ground-reaction times during running in men or women. Performing S before E caused greater (P<.01) oxygen uptake during running in both men and women than if E was performed before S, although heart rate and blood lactate were similar between ES and SE. CONCLUSIONS: Performing S before E increased oxygen uptake during E, which is explained, in part, by a decrease in MVC in both men and women, decreased CMJ and stride length in men, and/or an increase in postexercise oxygen consumption.

Concurrent endurance and explosive type strength training increases activation and fast force production of leg extensor muscles in endurance athletes.

The purpose of this experiment was to examine the effects of concurrent endurance and explosive strength training on electromyography (EMG) and force production of leg extensors, sport-specific rapid force production, aerobic capacity, and work economy in cross-country skiers. Nineteen male cross-country skiers were assigned to an experimental group (E, n = 8) or a control group (C, n = 11). The E group trained for 8 weeks with the same total training volume as C, but 27% of endurance training in E was replaced by explosive strength training. The skiers were measured at pre- and post training for concentric and isometric force-time parameters of leg extensors and EMG activity from the vastus lateralis (VL) and medialis (VM) muscles. Sport-specific rapid force production was measured by performing a 30-m double poling test with the maximal velocity (V(30DP)) and sport-specific endurance economy by constant velocity 2-km double poling test (CVDP) and performance (V(2K)) by 2-km maximal double poling test with roller skis on an indoor track. Maximal oxygen uptake (Vo(2)max) was determined during the maximal treadmill walking test with the poles. The early absolute forces (0-100 ms) in the force-time curve in isometric action increased in E by 18 +/- 22% (p < 0.05), with concomitant increases in the average integrated EMG (IEMG) (0-100 ms) of VL by 21 +/- 21% (p < 0.05). These individual changes in the average IEMG of VL correlated with the changes in early force (r = 0.86, p < 0.01) in E. V(30DP) increased in E (1.4 +/- 1.6%) (p < 0.05) but not in C. The V(2K) increased in C by 2.9 +/- 2.8% (p < 0.01) but not significantly in E (5.5 +/- 5.8%, p < 0.1). However, the steady-state oxygen consumption in CVDP decreased in E by 7 +/- 6% (p < 0.05). No significant changes occurred in Vo(2)max either in E or in C. The present concurrent explosive strength and endurance training in endurance athletes produced improvements in explosive force associated with increased rapid activation of trained leg muscles. The training also led to more economical sport-specific performance. The improvements in neuromuscular characteristics and economy were obtained without a decrease in maximal aerobic capacity, although endurance training was reduced by about 20%.

Neuromuscular factors determining 5 km running performance and running economy in well-trained athletes.

This study investigated the effects of the neuromuscular and force-velocity characteristics in distance running performance and running economy. Eighteen well-trained male distance runners performed five different tests: 20 m maximal sprint, running economy at the velocity of 4.28 m s(-1), 5 km time trial, maximal anaerobic running test (MART), and a treadmill test to determine VO2max. The AEMG ratio was calculated by the sum average EMG (AEMG) of the five lower extremity muscles during the 5 km divided by the sum AEMG of the same muscles during the maximal 20 m sprinting. The runners' capacity to produce power above VO2max (MART VO2gain) was calculated by subtracting VO2max from the oxygen demand of the maximal velocity in the MART (V MART). Velocity of 5 km (V 5K) correlated with V MART (r=0.77, p<0.001) and VO2max (r=0.49, p<0.05). Multiple linear regression analysis showed that MART VO2gain and VO2max explained 73% of the variation in V 5K. A significant relationship also existed between running economy and MART VO2gain (r=0.73, p<0.01). A significant correlation existed between V 5K and AEMG ratio during the ground contact phase at the 3 km (r=0.60, p<0.05) suggesting that neural input may affect distance running performance. The results of the present study support the idea that distance running performance and running economy are related to neuromuscular capacity to produce force and that the V MART can be used as a determinant of distance-running performance.