Speed Endurance Training Research Articles

Recovery Kinetics After Speed-Endurance Training in Male Soccer Players.

To determine the recovery kinetics of performance, muscle damage, and neuromuscular fatigue following 2 speed-endurance production training (SEPT) protocols in soccer. Ten well-trained, male soccer athletes randomly completed 3 trials: work-to-rest ratio (SEPT) 1:5, SEPT/1:8, and a control trial. Training load during SEPT was monitored using global positioning system and heart-rate monitors. Performance (isokinetic strength of knee extensors and flexors, speed, and countermovement jump) and muscle damage (delayed-onset muscle soreness [DOMS] and creatine kinase) were evaluated at baseline and at 0, 24, 48 and 72h posttraining. Maximal voluntary contraction (fatigue index) of knee extensors and flexors was additionally assessed at 1, 2, and 3h posttraining. Fatigue increased (P < .05) in SEPT/1:5 (∼4-30%) for 3h and in SEPT/1:8 (∼8-17%) for 2h. Strength performance declined (P < .05) in both SEPT trials (∼5-20%) for 48h. Speed decreased (∼4-18%; P < .05) for 72h in SEPT/1:5 and for 48h in SEPT/1:8. Countermovement-jump performance decreased (∼7-12%; P < .05) in both SEPT trials for 24h. DOMS increased (P < .05) in SEPT/1:5 (∼2-fold) for 72 and in SEPT/1:8 (∼1- to 2-fold) for 48h. Creatine kinase increased (∼1- to 2-fold, P < .05) in both SEPT trials for 72h. SEPT induces short-term neuromuscular fatigue; provokes a prolonged deterioration of strength (48h), speed (72h), and jump performance (24h); and is associated with a prolonged (72-h) rise of DOMS and creatine kinase. Time for recovery is reduced when longer work-to-rest ratios are applied. Fitness status may affect quality of SEPT and recovery kinetics.

Effects of auditory-motor synchronization on 400-m sprint performance: An applied study

There is a conspicuous dearth of empirical research regarding the ergogenic and psychological effects of synchronous music when applied in a sports training context. The main purpose of this longitudinal intervention study was to investigate the ergogenic and psychological effects of synchronous music applied over a one-month period of speed endurance training. Twelve participants (six women and six men; 21.1 ± 1.7 years) were randomly assigned to either an experimental group (sprint training coordinated with synchronous music) or a control group (conventional sprint training). Immediately after each training session and each time trial, the Feeling Scale, CR-10 Rating of Perceived Exertion Scale, and Physical Activity Enjoyment Scale were administered to each participant. No significant interaction effect of Group × Time for Rating of Perceived Exertion ( p = .898) or Physical Activity Enjoyment Scale ( p = .411) was identified during the training sessions. A significant Group × Time interaction was identified for Feeling Scale scores ( p = .007). Nonetheless, following Bonferroni adjustment for pairwise comparisons, the between-group differences in Feeling Scale scores did not reach significance. No significant interaction effect of Group × Time or main effect of group was identified for sprint performance, although the latter effect was associated with a large effect size (ηp2 = 0.35). Experimental group participants executed the 400-m time trials 5.07% faster than control group participants. This finding is noteworthy from an applied perspective, given the potential ergogenic effects associated with auditory-motor synchronization.

Combined Analysis of Blood Ammonia and Lactate Levels as a Practical Tool to Assess the Metabolic Response to Training Sessions in Male and Female Sprinters.

Kantanista, A, Kusy, K, Pospieszna, B, Korman, P, Wieliński, D, and Zieliński, J. Combined analysis of blood ammonia and lactate levels as a practical tool to assess the metabolic response to training sessions in male and female sprinters. J Strength Cond Res 35(9): 2591-2598, 2021-Previous research has mainly focused on blood ammonia and lactate concentration changes in response to exercise in laboratory settings. The aim of this study was to present a combined analysis of blood ammonia and lactate levels obtained during various training sessions performed under real training conditions. Differences between the sexes were also analyzed. The study subjects included 9 male and 8 female sprinters competing at the international level. The two-way analyses of variance, with repeated measures (time × sex), for lactate and blood ammonia concentrations during strength, speed (only lactate), speed with baton exchange, and speed endurance training sessions were significant. Blood ammonia and lactate levels obtained during repeated sprints were higher in male than female athletes. Peak lactate concentrations obtained from different training sessions were different in the female (F(3, 18) = 49.82, p ≤ 0.001, η2 = 0.893) and male (F(3, 21) = 312.26, p ≤ 0.001, η2 = 0.978) athletes; post hoc analyses of the men and women showed differences in maximum lactate concentration between training sessions, except in the speed and strength sessions. Peak ammonia concentrations obtained in the different training sessions were also different in the female (F(3, 18) = 121.06, p ≤ 0.001, η2 = 0.953) and male (F(3, 21) = 196.04, p ≤ 0.001, η2 = 0.965) athletes; in both the men and women, significant differences in maximum blood ammonia concentrations were found between the training sessions, except for the speed and speed with baton exchange training sessions. The results of this study indicate that the combined analysis of lactate and blood ammonia concentration provides the coach with valuable additional information about the level of adenosine triphosphate breakdown, the energy system contribution involved in muscle energy coverage during very short, repeated maximal sprints, and, most importantly, allows the coach to check whether preworkout goals were actually met.

Are two different speed endurance training protocols able to affect the concentration of serum cortisol in response to a shuttle run test in soccer players?

ABSTRACTSoccer involves multiple high-intensity physical, technical and tactical actions; as result of this, soccer training must include high-intensity exercises, which can act as a stimulus to the hypothalamus pituitary-adrenal axis, resulting in a significant increase in circulating cortisol levels. This study examined the effect of 4 weeks of Speed Endurance Maintenance (SEM) and Speed Endurance Production (SEP) on the serum cortisol concentration in response to a 5-meter multiple shuttle run test (5-m MST) in young elite soccer players. Fifteen soccer players were divided to SEM (n = 7) or SEP (n = 8) training group. Blood drawings were performed four times: before and after the 5-m MST at baseline (T1a, T1b) and at follow-up (T2a, T2b). Both training regimes determined a cortisol secretion following the 5-m MST at both baseline and follow-up. Data on delta values highlighted that SEP had greater values than SEM at baseline and registered a significant decrease at the follow-up. This difference is probably due to the lack of specific speed endurance training for players of SEP group prior to the beginning of the protocol. The physiological mechanisms behind the observed biological differences should be deeply investigated.

High-intensity exercise training enhances mitochondrial oxidative phosphorylation efficiency in a temperature-dependent manner in human skeletal muscle: implications for exercise performance.

The purpose of the present study was to investigate whether exercise training-induced adaptations in human skeletal muscle mitochondrial bioenergetics are magnified under thermal conditions resembling sustained intense contractile activity and whether training-induced changes in mitochondrial oxidative phosphorylation (OXPHOS) efficiency influence exercise efficiency. Twenty healthy men performed 6 wk of high-intensity exercise training [i.e., speed endurance training (SET; n = 10)], or maintained their usual lifestyle (n = 10). Before and after the intervention, mitochondrial respiratory function was determined ex vivo in permeabilized muscle fibers under experimentally-induced normothermia (35°C) and hyperthermia (40°C) mimicking in vivo muscle temperature at rest and during intense exercise, respectively. In addition, activity and content of muscle mitochondrial enzymes and proteins were quantified. Exercising muscle efficiency was determined in vivo by measurements of leg hemodynamics and blood parameters during one-legged knee-extensor exercise. SET enhanced maximal OXPHOS capacity and OXPHOS efficiency at 40°C, but not at 35°C, and attenuated hyperthermia-induced decline in OXPHOS efficiency. Furthermore, SET increased expression of markers of mitochondrial content and up-regulated content of MFN2, DRP1, and ANT1. Also, SET improved exercise efficiency and capacity. These findings indicate that muscle mitochondrial bioenergetics adapts to high-intensity exercise training in a temperature-dependent manner and that enhancements in mitochondrial OXPHOS efficiency may contribute to improving exercise performance.-Fiorenza, M., Lemminger, A. K., Marker, M., Eibye, K., Iaia, F. M., Bangsbo, J., Hostrup, M. High-intensity exercise training enhances mitochondrial oxidative phosphorylation efficiency in a temperature-dependent manner in human skeletal muscle: implications for exercise performance.

Effects of suggested speed endurance training program in some physiological variables after anaerobic effort for youths and advanced short distance runners

Effects of suggested speed endurance training program in some physiological variables after anaerobic effort for youths and advanced short distance runners

Effects of suggested speed endurance training program in some indicators of buffers systems in blood after anaerobic effort for youths and advanced short distance runners

Effects of suggested speed endurance training program in some indicators of buffers systems in blood after anaerobic effort for youths and advanced short distance runners

The effect of two different speed endurance training protocols on a multiple shuttle run performance in young elite male soccer players

ABSTRACTThere is not enough evidence on the impact of different speed endurance training regimes on footballers’ ability to perform multiple shuttle run performance. This study examined the effect of 4 weeks of speed endurance maintenance (SEM) and speed endurance production (SEP) training on the 5-meter multiple shuttle run test (5-m MST) performance in young elite soccer players. A parallel two-groups, longitudinal design was used. Fifteen players were divided to either SEM (8 repetitions of 20-s all-out sprint interspersed with 40 s of recovery) or SEP (8 repetitions of 20-s all-out bout interspersed with 120 s of recovery) training group. SEM improved the ability to tolerate fatigue and maintained the performance development during the 5-m MST while SEP increased only the 1st sprint showing, simultaneously, an increased fatigue index and performance decrement. The selection of which training regimes to prioritize should be based on the players’ characteristics and individual game requirementsAbbreviations: SEP: Speed Endurance Production; SEM: Speed Endurance Maintenance; PRE: Baseline; POST: End of experimental protocol; 5-m MST: 5-meters Multiple Shuttle Run Test; TD: Total Distance; FI: Fatigue Index; MSTdec: Percentage Decrement Score; BMI: Body Mass Index

Effect of speed endurance training and reduced training volume on running economy and single muscle fiber adaptations in trained runners.

The aim of the present study was to examine whether improved running economy with a period of speed endurance training and reduced training volume could be related to adaptations in specific muscle fibers. Twenty trained male (n = 14) and female (n = 6) runners (maximum oxygen consumption (VO2‐max): 56.4 ± 4.6 mL/min/kg) completed a 40‐day intervention with 10 sessions of speed endurance training (5–10 × 30‐sec maximal running) and a reduced (36%) volume of training. Before and after the intervention, a muscle biopsy was obtained at rest, and an incremental running test to exhaustion was performed. In addition, running at 60% vVO 2‐max, and a 10‐km run was performed in a normal and a muscle slow twitch (ST) glycogen‐depleted condition. After compared to before the intervention, expression of mitochondrial uncoupling protein 3 (UCP3) was lower (P < 0.05) and dystrophin was higher (P < 0.05) in ST muscle fibers, and sarcoplasmic reticulum calcium ATPase 1 (SERCA1) was lower (P < 0.05) in fast twitch muscle fibers. Running economy at 60% vVO 2‐max (11.6 ± 0.2 km/h) and at v10‐km (13.7 ± 0.3 km/h) was ~2% better (P < 0.05) after the intervention in the normal condition, but unchanged in the ST glycogen‐depleted condition. Ten kilometer performance was improved (P < 0.01) by 3.2% (43.7 ± 1.0 vs. 45.2 ± 1.2 min) and 3.9% (45.8 ± 1.2 vs. 47.7 ± 1.3 min) in the normal and the ST glycogen‐depleted condition, respectively. VO 2‐max was the same, but vVO 2‐max was 2.0% higher (P < 0.05; 19.3 ± 0.3 vs. 18.9 ± 0.3 km/h) after than before the intervention. Thus, improved running economy with intense training may be related to changes in expression of proteins linked to energy consuming processes in primarily ST muscle fibers.

Skeletal muscle and performance adaptations to high-intensity training in elite male soccer players: speed endurance runs versus small-sided game training

PurposeTo examine the skeletal muscle and performance responses across two different exercise training modalities which are highly applied in soccer training.MethodsUsing an RCT design, 39 well-trained male soccer players were randomized into either a speed endurance training (SET; n = 21) or a small-sided game group (SSG; n = 18). Over 4 weeks, thrice weekly, SET performed 6–10 × 30-s all-out runs with 3-min recovery, while SSG completed 2 × 7–9-min small-sided games with 2-min recovery. Muscle biopsies were obtained from m. vastus lateralis pre and post intervention and were subsequently analysed for metabolic enzyme activity and muscle protein expression. Moreover, the Yo–Yo Intermittent Recovery level 2 test (Yo–Yo IR2) was performed.ResultsMuscle CS maximal activity increased (P < 0.05) by 18% in SET only, demonstrating larger (P < 0.05) improvement than SSG, while HAD activity increased (P < 0.05) by 24% in both groups. Na+–K+ ATPase α1 subunit protein expression increased (P < 0.05) in SET and SSG (19 and 37%, respectively), while MCT4 protein expression rose (P < 0.05) by 30 and 61% in SET and SSG, respectively. SOD2 protein expression increased (P < 0.05) by 28 and 37% in SET and SSG, respectively, while GLUT-4 protein expression increased (P < 0.05) by 40% in SSG only. Finally, SET displayed 39% greater improvement (P < 0.05) in Yo–Yo IR2 performance than SSG.ConclusionSpeed endurance training improved muscle oxidative capacity and exercise performance more pronouncedly than small-sided game training, but comparable responses were in muscle ion transporters and antioxidative capacity in well-trained male soccer players.

A speed-endurance training to improve aerobic, anaerobic capacity, and fat oxidation of four groups of athletes

A speed-endurance training to improve aerobic, anaerobic capacity, and fat oxidation of four groups of athletes

The effect of repeated periods of speed endurance training on performance, running economy, and muscle adaptations.

The effect of repeated intense training interventions was investigated in eight trained male runners (maximum oxygen uptake [VO2 -max]: 59.3±3.2mL/kg/min, mean±SD) who performed 10 speed endurance training (SET; repeated 30-seconds "all-out" bouts) and 10 aerobic moderate-intensity training sessions during two 40-day periods (P1 and P2) separated by ~80days of habitual training. Before and after both P1 and P2, subjects completed an incremental test to exhaustion to determine VO2 -max and a repeated running test at 90% vVO2 -max to exhaustion (RRT) to determine short-term endurance capacity. In addition, running economy (RE) was measured at 60% vVO2 -max (11.9±0.5km/h) and v10-km (14.3±0.9km/h), a 10-km track-running test was performed, and a biopsy from m. vastus lateralis was collected. 10-km performance and VO2 -max (mL/min) were the same prior to P1 and P2, whereas RE was better (P<.05) before P2 than before P1. During P1 and P2, 10-km performance (2.9% and 2.3%), VO2 -max (2.1% and 2.6%), and RE (1.9% and 1.8% at 60% vVO2 -max; 1.6% and 2.0% at v10-km) improved (P<.05) to the same extent, respectively. Performance in RRT was 20% better (P<.05) after compared to before P2, with no change in P1. No changes in muscle expression of Na+ ,K+ -ATPase α1, α2 and β1, NHE1, SERCA1 and SERCA2, actin, and CaMKII were found during neither P1 nor P2. Thus, the present study demonstrates that a second period of intense training leads to improved short-term performance and further improved RE, whereas 10-km performance and VO2 -max improve to the same extent as during the first period.

Effect of increased and maintained frequency of speed endurance training on performance and muscle adaptations in runners.

Ten speed endurance training (SET) sessions improved short-term exercise capacity and 10-km performance, which was followed by further improved short-term exercise capacity, but unchanged 10-km performance after 20 SET sessions performed with either high frequency (4 per 8 days) or continued low frequency (2 per 8 days) in trained runners. The further gain in short-term exercise capacity was associated with changes in muscle expression of proteins of importance for the development of fatigue.

Limitations in intense exercise performance of athletes - effect of speed endurance training on ion handling and fatigue development.

Mechanisms underlying fatigue development and limitations for performance during intense exercise have been intensively studied during the past couple of decades. Fatigue development may involve several interacting factors and depends on type of exercise undertaken and training level of the individual. Intense exercise (½-6min) causes major ionic perturbations (Ca2+ , Cl- , H+ , K+ , lactate- and Na+ ) that may reduce sarcolemmal excitability, Ca2+ release and force production of skeletal muscle. Maintenance of ion homeostasis is thus essential to sustain force production and power output during intense exercise. Regular speed endurance training (SET), i.e. exercise performed at intensities above that corresponding to maximum oxygen consumption (V̇O2, max ), enhances intense exercise performance. However, most of the studies that have provided mechanistic insight into the beneficial effects of SET have been conducted in untrained and recreationally active individuals, making extrapolation towards athletes' performance difficult. Nevertheless, recent studies indicate that only a few weeks of SET enhances intense exercise performance in highly trained individuals. In these studies, the enhanced performance was not associated with changes in V̇O2, max and muscle oxidative capacity, but rather with adaptations in muscle ion handling, including lowered interstitial concentrations of K+ during and in recovery from intense exercise, improved lactate- -H+ transport and H+ regulation, and enhanced Ca2+ release function. The purpose of this Topical Review is to provide an overview of the effect of SET and to discuss potential mechanisms underlying enhancements in performance induced by SET in already well-trained individuals with special emphasis on ion handling in skeletal muscle.

How Do World-Class Nordic Combined Athletes Differ From Specialized Cross-Country Skiers and Ski Jumpers in Sport-Specific Capacity and Training Characteristics?

To compare sport-specific laboratory capacities and the annual training of world-class Nordic combined (NC) athletes with specialized ski jumpers (SJ) and cross-country (XC) skiers. Five world-class athletes from each sports discipline were compared. Ski jump imitations were performed on a 3-dimensional force plate in NC athletes and SJ, whereas XC skiing characteristics were obtained from submaximal and maximal roller ski skating on a treadmill in NC athletes and XC skiers. In addition, anthropometrics and annual training characteristics were determined. NC athletes demonstrated 9% higher body mass and showed 17% lower vertical speed in the ski jump imitation than SJ (all P < .05). NC athletes had 12% lower body mass and showed 10% lower peak treadmill speed and 12% lower body-mass-normalized peak oxygen uptake than XC skiers (all P < .05). NC athletes performed half the number of ski-jumping-specific sessions and outdoor ski jumps compared with SJ. NC athletes performed 31% less endurance training, mainly caused by lower amounts of low- and moderate-intensity training in the classical technique, whereas high-intensity strength and speed training and endurance training in the skating technique did not differ substantially from XC skiers. To simultaneously optimize endurance, explosive, and technical capacities in 2 different disciplines, world-class NC athletes train approximately two-thirds of the XC skier's endurance training volume and perform one-half of the ski-jump-specific training compared with SJ. Still, the various laboratory capacities differed only 10-17% compared with SJ and XC skiers.

Changes in body surface temperature during speed endurance work-out in highly-trained male sprinters

The mechanism of thermoregulatory adaptation to exercise cannot yet be fully explained, however, infrared thermography (IRT) seems to have potential for monitoring physiological changes during exercise and training. It is a non-contact and easy to use technology to measure heat radiation from the body surface.The objective of the study was to examine the temperature changes over time on lower limbs in sprinters during speed endurance training session.Eight sprinters, specialized in distances 100m and 200m, aged 21–29years, members of the Polish national team, were evaluated during an outdoor speed endurance work-out. Their track session comprised of warm-up, specific drills for sprinting technique, and speed endurance exercise. The surface temperature of lower limbs was measured and thermal images were taken using infrared camera after each part of the session.The speed endurance training session brought about specific time course of body surface (legs) temperature. The warm-up induced a significant decline in surface temperature by ∼2.5°C, measured both on the front and back of lower limbs (p<0.001), followed by a temperature stabilization until the end of the session. No significant asymmetry between the front and back sides of legs was observed.Body surface temperature may help identify an individual optimal time to terminate warm up and start the main part of the training session. It may also be useful for the assessment of muscle activity symmetry in cyclical activities, such as sprint running. This is of particular relevance when a training session is performed outdoors in changeable weather conditions.

Adaptations to Speed Endurance Training in Highly Trained Soccer Players.

The present study examined whether a period of additional speed endurance training would improve intense intermittent exercise performance in highly trained soccer players during the season and whether the training changed aerobic metabolism and the level of oxidative enzymes in type I and type II muscle fibers. During the last 9 wk of the season, 13 semiprofessional soccer players performed additional speed endurance training sessions consisting of two to three sets of 8-10 repetitions of 30-m sprints with 10 s of passive recovery (SET). Before and after SET, subjects completed a double-step exercise protocol that included transitions from standing to moderate-intensity running (~75% HRmax), followed by transitions from moderate- to high-intensity running (~90% HRmax) in which pulmonary oxygen uptake (V˙O2) was determined. In addition, the yo-yo intermittent recovery test level 1 was performed, and a muscle biopsy was obtained at rest. The yo-yo intermittent recovery test level 1 performance was 11.6% ± 6.4% (mean ± SD) better (2803 ± 330 vs 3127 ± 383 m, P < 0.05) after SET compared with before SET. In the transition from standing to moderate-intensity running, phase II pulmonary V˙O2 kinetics was 11.4% ± 16.5% faster (P < 0.05), and the running economy at this intensity was 2.3% ± 3.0% better (P < 0.05). These improvements were apparent despite the content of muscle proteins regulating oxidative metabolism (3-hydroxyacyl CoA dehydrogenase, COX IV, and OXPHOS), and capillarization was reduced (P < 0.05). The content of 3-hydroxyacyl CoA dehydrogenase and citrate synthase in type I and type II fibers did not change. In highly trained soccer players, additional speed endurance training is associated with an improved ability to perform repeated high-intensity work. To what extent the training-induced changes in V˙O2 kinetics and mechanical efficiency in type I fibers caused the improvement in performance warrants further investigation.

Comparison between two types of anaerobic speed endurance training in competitive soccer players.

The purpose of the present study was to examine the effects of additional in-season speed endurance production versus speed endurance maintenance training regimes on performance in competitive male soccer players. In a randomised controlled trial 18 male sub-elite players were exposed to additional speed endurance production (SEP) or speed endurance maintenance (SEM) training (two additional sessions/wk for 4 weeks) during the competitive season. Players performed the Yo-Yo intermittent recovery level 2 test (YYIR2) and a repeated sprint test (RST) pre- and post-intervention. Yo-Yo IR2 performance increased (p<0.001) by 50 ± 8% and 26 ± 5% in SEP and SEM, respectively, with greater (p=0.03) improvement in SEP. RST performance improved by 2.1 ± 0.3% and 1.3 ± 0.4% in SEP and SEM, respectively, while the RST fatigue index decreased (4.4 ± 0.8 to 3.4 ± 0.5%; p<0.04) in SEP only. Peak and average speed during training were higher (p<0.001) in SEP than in SEM (24.5 ± 0.3 vs 19.2 ± 0.3 and 15.5 ± 0.1 km·h-1 vs 9.4 ± 0.1 km·h-1). Additional in-season anaerobic speed endurance production and maintenance training improves high-intensity exercise performance in competitive soccer players with superior effects of speed endurance production training.

Effect of speed endurance and strength training on performance, running economy and muscular adaptations in endurance-trained runners.

To investigate the effects of combined strength and speed endurance (SE) training along with a reduced training volume on performance, running economy and muscular adaptations in endurance-trained runners. Sixteen male endurance runners (VO2-max: ~60mlkg(-1)min(-1)) were randomly assigned to either a combined strength and SE training (CSS; n=9) or a control (CON; n=7) group. For 8weeks, CSS replaced their normal moderate-intensity training (~63kmweek(-1)) with SE (2×week(-1)) and strength training (2×week(-1)) as well as aerobic high (1×week(-1)) and moderate (1×week(-1)) intensity training with a reduction in total volume of~58%, whereas CON continued their training (~45kmweek(-1)). In CSS, 400-m and Yo-Yo intermittent recovery test performance was improved by 5% (P<0.01) and 19% (P<0.001), respectively, during the intervention period. Maximal aerobic speed was 0.6kmh(-1) higher (P<0.05), and maximal activity of lactate dehydrogenase subunits 1 and 2 was 17% (P<0.05) higher after compared to before the intervention period. Time to exhaustion and peak blood lactate during an incremental treadmill test was 9% (P<0.05) and 32% (P<0.01), respectively, higher and expression of Na(+)-K(+) pump β1 subunit was 15% higher (P<0.05) after compared to before the intervention period. 10-K performance, maximum oxygen uptake and running economy were unchanged. In CON, no changes were observed. Adding strength and speed endurance training, along with a reduced training volume, can improve short-term exercise capacity and induce muscular adaptations related to anaerobic capacity in endurance-trained runners.

Performance in sports--With specific emphasis on the effect of intensified training.

Performance in most sports is determined by the athlete's technical, tactical, physiological and psychological/social characteristics. In the present article, the physical aspect will be evaluated with a focus on what limits performance, and how training can be conducted to improve performance. Specifically how intensified training, i.e., increasing the amount of aerobic high-intensity and speed endurance training, affects physiological adaptations and performance of trained subjects. Periods of speed endurance training do improve performance in events lasting 30 s-4 min, and when combined with aerobic high-intensity sessions, also performance during longer events. Athletes in team sports involving intense exercise actions and endurance aspects, such as soccer and basketball, can also benefit from intensified training. Speed endurance training does reduce energy expenditure and increase expression of muscle Na(+), K(+) pump α subunits, which may preserve muscle cell excitability and delay fatigue development during intense exercise. When various types of training are conducted in the same period (concurrent training), as done in a number of sports, one type of training may blunt the effect of other types of training. It is not, however, clear how various training modalities are affecting each other, and this issue should be addressed in future studies.