The purpose of this study was to investigate effects of concurrent strength and endurance training (SE) (2 plus 2 days a week) versus strength training only (S) (2 days a week) in men [SE: n=11; 38 (5) years, S: n=16; 37 (5) years] over a training period of 21 weeks. The resistance training program addressed both maximal and explosive strength components. EMG, maximal isometric force, 1 RM strength, and rate of force development (RFD) of the leg extensors, muscle cross-sectional area (CSA) of the quadriceps femoris (QF) throughout the lengths of 4/15-12/15 (L(f)) of the femur, muscle fibre proportion and areas of types I, IIa, and IIb of the vastus lateralis (VL), and maximal oxygen uptake (VO(2max)) were evaluated. No changes occurred in strength during the 1-week control period, while after the 21-week training period increases of 21% (p<0.001) and 22% (p<0.001), and of 22% (p<0.001) and 21% (p<0.001) took place in the 1RM load and maximal isometric force in S and SE, respectively. Increases of 26% (p<0.05) and 29% (p<0.001) occurred in the maximum iEMG of the VL in S and SE, respectively. The CSA of the QF increased throughout the length of the QF (from 4/15 to 12/15 L(f)) both in S (p<0.05-0.001) and SE (p<0.01-0.001). The mean fibre areas of types I, IIa and IIb increased after the training both in S (p<0.05 and 0.01) and SE (p<0.05 and p<0.01). S showed an increase in RFD (p<0.01), while no change occurred in SE. The average iEMG of the VL during the first 500 ms of the rapid isometric action increased (p<0.05-0.001) only in S. VO(2max) increased by 18.5% (p<0.001) in SE. The present data do not support the concept of the universal nature of the interference effect in strength development and muscle hypertrophy when strength training is performed concurrently with endurance training, and the training volume is diluted by a longer period of time with a low frequency of training. However, the present results suggest that even the low-frequency concurrent strength and endurance training leads to interference in explosive strength development mediated in part by the limitations of rapid voluntary neural activation of the trained muscles.

To investigate the effects of simultaneous explosive‐strength and endurance training on physical performance characteristics, 10 experimental (E) and eight control (C) endurance athletes trained for 9 weeks. The total training volume was kept the same in both groups, but 32% of training in E and 3% in C was replaced by explosive‐type strength training. A 5‐km time trial (5K), running economy (RE), maximal 20‐m speed (V20 m), and 5‐jump (5J) tests were measured on a track. Maximal anaerobic (MART) and aerobic treadmill running tests were used to determine maximal velocity in the MART (VMART) and maximal oxygen uptake (VO2 max). The 5K time, RE, and VMART improved (P<0.05) in E, but no changes were observed in C. V20 m and 5J increased in E (P<0.01) and decreased in C (P<0.05). VO2 max increased in C (P<0.05), but no changes were observed in E. In the pooled data, the changes in the 5K velocity during 9 weeks of training correlated (P<0.05) with the changes in RE [O2 uptake (r=−0.54)] and VMART (r=0.55). In conclusion, the present simultaneous explosive‐strength and endurance training improved the 5K time in well‐trained endurance athletes without changes in their VO2 max. This improvement was due to improved neuromuscular characteristics that were transferred into improved VMART and running economy.

To investigate the effects of simultaneous explosive-strength and endurance training on physical performance characteristics, 10 experimental (E) and 8 control (C) endurance athletes trained for 9 wk. The total training volume was kept the same in both groups, but 32% of training in E and 3% in C was replaced by explosive-type strength training. A 5-km time trial (5K), running economy (RE), maximal 20-m speed (V20 m), and 5-jump (5J) tests were measured on a track. Maximal anaerobic (MART) and aerobic treadmill running tests were used to determine maximal velocity in the MART (VMART) and maximal oxygen uptake (VO2 max). The 5K time, RE, and VMART improved (P < 0.05) in E, but no changes were observed in C. V20 m and 5J increased in E (P < 0.01) and decreased in C (P < 0.05). VO2 max increased in C (P < 0.05), but no changes were observed in E. In the pooled data, the changes in the 5K velocity during 9 wk of training correlated (P < 0.05) with the changes in RE [O2 uptake (r = -0.54)] and VMART (r = 0.55). In conclusion, the present simultaneous explosive-strength and endurance training improved the 5K time in well-trained endurance athletes without changes in their VO2 max. This improvement was due to improved neuromuscular characteristics that were transferred into improved VMART and running economy.

We conclude that neuromuscular characteristics and VMART were related to 5-km running performance in well trained endurance athletes. Relationships between VMART and neuromuscular and anaerobic characteristics suggest that VMART can be used as a measure of muscle power in endurance athletes.

This study investigated neuromuscular characteristics and fatigue during 10 km running (10 K) performance in well-trained endurance athletes with different distance running capability. Nine high (HC) and ten low (LC) caliber endurance athletes performed the 10 K on a 200 m indoor track, constant velocity lap (CVL, 4.5 m x s(-1)) 5 times during the course of the 10 K and maximal 20 m speed test before (20 m(b)) and after (20 m(a)) the 10 K. Running velocity (V), ground contact times (CT), ground reaction forces (F) and electromyographic activity (EMG) of the leg muscles (vastus lateralis; VL, biceps femoris; BF, gastrocnemius; GA) were measured during 20 m(b), 20 m(a), and CVLs. The 10 K times differed (p<0.001) between HC and LC (36.3+/-1.2 and 39.2+/-2.0 min, respectively) but no differences were observed in 20 m(b) velocity. The 10 K led to significant (p<0.05) decreases in V, F and integrated EMG (IEMG) and increases in CTs of 20 m(a) in both groups. No changes were observed in HC or LC in F and IEMG during the CVLs but HC showed shorter (p<0.05) mean CT of CVLs than LC. A significant correlation (r = -0.56, p<0.05) was observed between the mean CT of CVLs and velocity of 10 K (V10K). Pre-activity of GA in relation to the IEMG of the total contact phase during the CVLs was higher (p<0.05) in HC than LC. The relative IEMGs of VL and GA in the propulsion phase compared to the IEMG of the 20 m(b) were lower (p<0.05) in HC than LC. In conclusion, marked fatigue took place in both HC and LC during the 10 K but the fatigue-induced changes in maximal 20 m run did not differentiate endurance athletes with different V10K. However, a capability to produce force rapidly throughout the 10 K accompanied with optimal preactivation and contact phase activation seem to be important for 10 km running performance in well trained endurance 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.

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%.

This study was carried out to investigate the importance of maximal oxygen uptake (VO2max) and so-called muscle power factors relating to neuromuscular and anaerobic characteristics as determinants of peak horizontal and uphill treadmill running velocity (Vmax). Muscle power factors were measured as peak velocity (VMART) and blood lactate concentration (BlaMART) in a maximal anaerobic running test and as maximal 30-m run velocity (V30m). Seven middle-distance runners, eight triathletes and eight cross-country skiers performed an incremental VO2max-test at horizontal (subscript max0) and 7 degrees uphill (subscript max7) and the MART at 3 degrees uphill on a treadmill and V30m-test on a track. The MART consisted of n x 20-s runs with a 100-s recovery between the runs and the velocity was increased by 0.41 m x s(-1) for each consecutive run until exhaustion. At 0 degrees Vmax was significantly higher but VO2max, ventilation and Bla were significantly lower than at 7 degrees inclination. Vmax0 correlated with VMART (r=0.85, P<0.001), Blamax0 (r=0.49, P<0.05) and V30m (r=0.78, P<0.001) but not with VO2max0. Vmax7 correlated with VO2max7 (r=0.78, P<0.001), VMART (r=0.61, P<0.01) and V30m (r=0.53, P<0.05). VMART correlated with BlaMART (r=0.71, P<0.01) and V30m (r=0.96, P<0.001) but not with VO2max0 or VO2max7. Middle-distance runners had a significantly (P<0.001) higher Vmax0, VMART BlaMART and V30m than triathletes and cross-country skiers, but no significant differences were found between the three groups in VO2max0, VO2max7 or Vmax7. We conclude that so-called muscle power factors, e.g. VMART, V30m and BlaMART, contribute to peak treadmill running performance and especially to horizontal running performance and that VO2max contributes more to uphill than horizontal running performance.