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The aim of this study was to analyze the influence of natural turf, artificial turf, and sand on sprint performance in different sports and to determine how the sport surface affects sprint performance. A systematic search was conducted in Pubmed, Web of Sciences, and SPORTDiscus databases. Out of 5644 studies, 11 studies were included in the meta-analysis. The studies were very heterogeneous, as they examined different structural characteristics or quality parameters. The studies on natural turf and sand showed significant improvements on sprint speed during training. On the other hand, the analysis of fatigue did not reveal significant differences in the deterioration of sprint speed on both natural and artificial turf. Significance was set at p < 0.05. In conclusion, although lower performance in sprint was reported on sand, further studies are needed to explain the differences in sprint on natural and artificial turf., Competing Interests: The authors declare no conflict of interest.

Background: Protein supplementation has been suggested to augment endurance training adaptations by increasing mixed muscle and myofibrillar protein synthesis and lean body mass. However, a potential beneficial effect on mitochondrial adaptations is yet to be clarified. The aim of the present study was to investigate the effect of consuming whey protein hydrolysate before and whey protein hydrolysate plus carbohydrate (PRO-CHO) after each exercise session during a six-week training period compared to similarly timed intake of isocaloric CHO supplements on biomarkers of mitochondrial biogenesis, VO 2max and performance in trained runners., Methods: Twenty-four trained runners (VO 2max 60.7 ± 3.7 ml O 2 kg - 1  min 1 ) completed a six-week block randomized controlled intervention period, consisting of progressive running training. Subjects were randomly assigned to either PRO-CHO or CHO and matched in pairs for gender, age, VO 2max , training and performance status. The PRO-CHO group ingested a protein beverage (0.3 g kg - 1 ) before and protein-carbohydrate beverage (0.3 g protein kg - 1 and 1 g carbohydrate kg - 1 ) after each exercise session. The CHO group ingested an energy matched carbohydrate beverage. Resting muscle biopsies obtained pre and post intervention were analyzed for mitochondrial specific enzyme activity and mitochondrial protein content. Subjects completed a 6 K time trial (6 K TT) and a VO 2max test pre, midway (only 6 K TT) and post intervention., Results: Following six weeks of endurance training Cytochrome C (Cyt C) protein content was significantly higher in the PRO-CHO group compared to the CHO group (p < 0.05), with several other mitochondrial proteins (Succinate dehydrogenase (SDHA), Cytochrome C oxidase (COX-IV), Voltage-dependent anion channel (VDAC), Heat shock protein 60 (HSP60), and Prohibitin (PHB1)) following a similar, but non-significant pattern (p = 0.07-0.14). β-hydroxyacyl-CoA dehydrogenase (HAD) activity was significantly lower after training in the CHO group (p < 0.01), but not in the PRO-CHO group (p = 0.24). VO 2max and 6 K TT was significantly improved after training with no significant difference between groups., Conclusion: Intake of whey PRO hydrolysate before and whey PRO hydrolysate plus CHO after each exercise session during a six-week endurance training period may augment training effects on specific mitochondrial proteins compared to intake of iso-caloric CHO but does not alter VO 2max or 6 K TT performance., Trial Registration: clinicaltrials.gov , NCT03561337 . Registered 6 June 2018 - Retrospectively registered.

This study investigated the in-season effect of intensified training comparing the efficacy of duration-matched intense intermittent exercise training with sprint interval training in increasing intermittent running performance, sprint ability, and muscle content of proteins related to ion handling and metabolism in football players. After the first two weeks in the season, 22 sub-elite football players completed either 10 weeks of intense intermittent training using the 10-20-30 training concept (10-20-30, n = 12) or sprint interval training (SIT, n = 10; work/rest ratio: 6-s/54-s) three times weekly, with a ~20% reduction in weekly training time. Before and after the intervention, players performed a Yo-Yo intermittent recovery test level 1 (Yo-Yo IR1) and a 30-m sprint test. Furthermore, players had a muscle biopsy taken from the vastus lateralis. Yo-Yo IR1 performance increased by 330 m (95%CI: 178-482, P ≤ 0.01) in 10-20-30, whereas no change was observed in SIT. Sprint time did not change in 10-20-30 but decreased by 0.04 second (95%CI: 0.00-0.09, P ≤ 0.05) in SIT. Muscle content of HADHA (24%, P ≤ 0.01), PDH-E1α (40%, P ≤ 0.01), complex I-V of the electron transport chain (ETC) (51%, P ≤ 0.01) and Na + , K + -ATPase subunits α 2 (33%, P ≤ 0.05) and β 1 (27%, P ≤ 0.05) increased in 10-20-30, whereas content of DHPR (27%, P ≤ 0.01) and complex I-V of the ETC (31%, P ≤ 0.05) increased in SIT. Intense intermittent training, combining short sprints and a high aerobic load, is superior to regular sprint interval training in increasing intense intermittent running performance during a Yo-Yo IR1 test and muscle content of PDH-E1α and HADHA in sub-elite football players., (© 2019 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

The present study examined the effect of intense intermittent running with 5 s sprints on body composition, fitness level, and performance in untrained subjects aged 36-53 years. For 7 weeks, the subjects carried out 3 days a week 5-10-15 training consisting of 3-9 blocks of 4 repetitions of 15, 10, and 5 s low-, moderate-, and high-speed running, respectively. Body fat mass was 4.3% lower (P < 0.01), and lean body mass and bone mineral density was 1.1 and 0.9% higher (P < 0.01), respectively, after compared to before the intervention period (INT). The plasma bone turnover markers osteocalcin increased (P < 0.01) by 147%, and procollagen-type I N propeptide and carboxy-terminal collagen crosslinks increased (P < 0.05) by 84 and 76%, respectively. Furthermore, the training improved performance in 1500 m (P < 0.001), 3 km (P < 0.001), Yo-Yo intermittent endurance test (P < 0.01), and incremental treadmill running (P < 0.001) by 8.1, 9.9, 17.2, and 23.9%, respectively. Furthermore, blood lactate after running at 85% of maximal aerobic speed was lower (P < 0.01) after compared to before the INT. Thus, 7 weeks of 5-10-15 training resulted in significant health beneficial changes and better performance in untrained subject.

The effect of repeated intense training interventions was investigated in eight trained male runners (maximum oxygen uptake [VO 2 -max]: 59.3±3.2 mL/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 ~80 days of habitual training. Before and after both P1 and P2, subjects completed an incremental test to exhaustion to determine VO 2 -max and a repeated running test at 90% vVO 2 -max to exhaustion (RRT) to determine short-term endurance capacity. In addition, running economy (RE) was measured at 60% vVO 2 -max (11.9±0.5 km/h) and v10-km (14.3±0.9 km/h), a 10-km track-running test was performed, and a biopsy from m. vastus lateralis was collected. 10-km performance and VO 2 -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%), VO 2 -max (2.1% and 2.6%), and RE (1.9% and 1.8% at 60% vVO 2 -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 VO 2 -max improve to the same extent as during the first period., (© 2017 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

The effect of tapering following a period of high-volume sprint interval training (SIT) and a basic volume of aerobic training on performance and muscle adaptations in moderately trained runners was examined. Eleven (8 men, 3 women) runners [maximum oxygen uptake (V̇o 2max ): 56.8 ± 2.9 ml·min -1 ·kg -1 ; mean ± SD] conducted high-volume SIT (HV; 20 SIT sessions; 8-12 × 30 s all-out) for 40 days followed by 18 days of tapering (TAP; 4 SIT sessions; 4 × 30 s all-out). Before and after HV as well as midway through and at the end of TAP, the subjects completed a 10-km running test and a repeated running test at 90% of vV̇o 2max to exhaustion (RRT). In addition, a biopsy from the vastus lateralis muscle was obtained at rest. Performance during RRT was better ( P < 0.01) at the end of TAP than before HV (6.8 ± 0.5 vs. 5.6 ± 0.5 min; means ± SE), and 10-km performance was 2.7% better ( P < 0.05) midway through (40.7 ± 0.7 min) and at the end of (40.7 ± 0.6 min) TAP than after HV (41.8 ± 0.9 min). The expression of muscle Na + -K + -ATPase (NKA)α 1 , NKAβ 1 , phospholemman (FXYD1), and sarcoplasmic reticulum calcium transport ATPase (SERCA1) increased ( P < 0.05) during HV and remained higher during TAP. In addition, oxygen uptake at 60% of vV̇o 2max was lower ( P < 0.05) at the end of TAP than before and after HV. Thus short-duration exercise capacity and running economy were better than before the HV period together with higher expression of muscle proteins related to Na + /K + transport and Ca 2+ reuptake, while 10-km performance was not significantly improved by the combination of HV and tapering. NEW & NOTEWORTHY Short-duration performance became better after 18 days of tapering from ~6 wk of high-volume sprint interval training (SIT), whereas 10-km performance was not significantly affected by the combination of high-volume SIT and tapering. Higher expression of muscle NKAα 1 , NKAβ 1 , FXYD1, and SERCA1 may reflect faster Na + /K + transport and Ca 2+ reuptake that could explain the better short-duration performance. These results suggest that the type of competition should determine the duration of tapering to optimize performance.

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 (VO 2 -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., (© 2018 The Authors. Physiological Reports published by Wiley Periodicals, Inc. on behalf of The Physiological Society and the American Physiological Society.)

The aim of the study was, in runners accustomed to speed endurance training (SET), to examine the effect of increased and maintained frequency of SET on performance and muscular adaptations. After familiarization (FAM) to SET, 18 male (n = 14) and female (n = 4) runners (V̇o 2max : 57.3 ± 3.4 ml/min; means ± SD) completed 20 sessions of maintained low-frequency (LF; every fourth day; n = 7) or high-frequency (HF; every second day; n = 11) SET. Before FAM as well as before and after an intervention period (INT), subjects completed a series of running tests and a biopsy from m. vastus lateralis was collected. Ten-kilometer performance improved (P < 0.05) ~3.5% during FAM with no further change during INT. Time to exhaustion at 90% vV̇o 2max was 15 and 22% longer (P < 0.05) during FAM and a further 12 and 16% longer (P < 0.05) during INT in HF and LF, respectively. During FAM, muscle expression of NHE1 and maximal activity of citrate synthase (CS) and phosphofructokinase (PFK) increased (P < 0.05), running economy (RE) improved (P < 0.05), and V̇o 2max was unchanged. During INT, both HF and LF increased (P < 0.05) muscle expression of NKAβ1, whereas maximal activity of CS and PFK, RE, and V̇o 2max were unchanged. Furthermore, during INT, muscle expression of FXYD1 and SERCA1, and FXYD1 activity increased (P < 0.05) in HF, while muscle expression of SERCA2 decreased (P < 0.05) in LF. Thus increased or maintained frequency of SET leads to further improvements in short-term exercise capacity, but not in 10-km running performance. The better short-term exercise capacity may be associated with elevated expression of muscle proteins related to Na + /K + transportation and Ca 2+ reuptake., New & Noteworthy: 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., (Copyright © 2017 the American Physiological Society.)

Purpose: 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., Methods: Sixteen male endurance runners (VO2-max: ~60 ml kg(-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 8 weeks, CSS replaced their normal moderate-intensity training (~63 km week(-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 (~45 km week(-1))., Results: 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 0.6 km h(-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., Conclusions: 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.

The aim was to investigate the effect of the long-acting β2-adrenergic agonist formoterol on muscle strength and power output, muscle metabolism, and phosphorylation of CaMKII Thr(287) and FXYD1 during maximal sprinting. In a double-blind crossover study, 13 males [V̇o2 max: 45.0 ± 0.2 (means ± SE) ml·min(-1)·kg(-1)] performed a 30-s cycle ergometer sprint after inhalation of either 54 μg of formoterol (FOR) or placebo (PLA). Before and after the sprint, muscle biopsies were collected from vastus lateralis and maximal voluntary contraction (MVC), and contractile properties of quadriceps were measured. Oxygen uptake was measured during the sprint. During the sprint, peak power, mean power, and end power were 4.6 ± 0.8, 3.9 ± 1.1, and 9.5 ± 3.2% higher (P < 0.05) in FOR than in PLA, respectively. Net rates of glycogenolysis and glycolysis were 45.7 ± 21.0 and 28.5 ± 13.4% higher (P < 0.05) in FOR than in PLA, respectively, and the decrease in ATP content was lower (P < 0.05) in FOR than in PLA (3.7 ± 1.5 vs. 8.0 ± 1.6 mmol/kg dry weight). There was no difference in breakdown of phosphocreatine and oxygen uptake between treatments. Before and after the sprint, MVC and peak twitch force were higher (P < 0.05) in FOR than in PLA. No differences were observed in phosphorylation of CaMKII Thr(287) and FXYD1 between treatments before the sprint, whereas phosphorylation of CaMKII Thr(287) and FXYD1 was greater (P < 0.05) in FOR than in PLA after the sprint. In conclusion, formoterol-induced enhancement in power output during maximal sprinting is associated with increased rates of glycogenolysis and glycolysis that may counteract development of fatigue., (Copyright © 2016 the American Physiological Society.)

The present study examined the effect of training by the 10-20-30 concept on performance, blood pressure (BP), and skeletal muscle angiogenesis as well as the feasibility of completing high-intensity interval training in local running communities. One hundred sixty recreational runners were divided into either a control group (CON; n = 28), or a 10-20-30 training group (10-20-30; n = 132) replacing two of three weekly training sessions with 10-20-30 training for 8 weeks and performance of a 5-km run (5-K) and BP was measured. VO2max was measured and resting muscle biopsies were taken in a subgroup of runners (n = 18). 10-20-30 improved 5-K time (38 s) and lowered systolic BP (2 ± 1 mmHg). For hypertensive subjects in 10-20-30 (n = 30), systolic and diastolic BP was lowered by 5 ± 4 and 3 ± 2 mmHg, respectively, which was a greater reduction than in the non-hypertensive subjects (n = 102). 10-20-30 increased VO2max but did not influence muscle fiber area, distribution or capillarization, whereas the expression of the pro-angiogenic vascular endothelial growth factor (VEGF) was lowered by 22%. No changes were observed in CON. These results suggest that 10-20-30 training is an effective and easily implemented training intervention improving endurance performance, VO2max and lowering BP in recreational runners, but does not affect muscle morphology and reduces muscle VEGF., (© 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

In order to better understand the specificity of training adaptations, we compared the effects of two different anaerobic training regimes on various types of soccer-related exercise performances. During the last 3 weeks of the competitive season, thirteen young male professional soccer players (age 18.5±1 yr, height 179.5±6.5 cm, body mass 74.3±6.5 kg) reduced the training volume by ~20% and replaced their habitual fitness conditioning work with either speed endurance production (SEP; n = 6) or speed endurance maintenance (SEM; n = 7) training, three times per wk. SEP training consisted of 6-8 reps of 20-s all-out running bouts followed by 2 min of passive recovery, whereas SEM training was characterized by 6-8 x 20-s all-out efforts interspersed with 40 s of passive recovery. SEP training reduced (p<0.01) the total time in a repeated sprint ability test (RSAt) by 2.5%. SEM training improved the 200-m sprint performance (from 26.59±0.70 to 26.02±0.62 s, p<0.01) and had a likely beneficial impact on the percentage decrement score of the RSA test (from 4.07±1.28 to 3.55±1.01%) but induced a very likely impairment in RSAt (from 83.81±2.37 to 84.65±2.27 s). The distance covered in the Yo-Yo Intermittent Recovery test level 2 was 10.1% (p<0.001) and 3.8% (p<0.05) higher after SEP and SEM training, respectively, with possibly greater improvements following SEP compared to SEM. No differences were observed in the 20- and 40-m sprint performances. In conclusion, these two training strategies target different determinants of soccer-related physical performance. SEP improved repeated sprint and high-intensity intermittent exercise performance, whereas SEM increased muscles' ability to maximize fatigue tolerance and maintain speed development during both repeated all-out and continuous short-duration maximal exercises. These results provide new insight into the precise nature of a stimulus necessary to improve specific types of athletic performance in trained young soccer players.

This trial aimed to examine the effect of whey protein hydrolysate intake before and after exercise sessions on endurance performance and recovery in elite orienteers during a training camp. Eighteen elite orienteers participated in a randomized controlled intervention trial during a 1-week training camp (13 exercise sessions). Half of the runners (PRO-CHO) ingested a protein drink before (0.3 g kg(-1)) and a protein-carbohydrate drink after (0.3 g protein kg(-1) and 1 g carbohydrate kg(-1)) each exercise session. The others ingested energy and time-matched carbohydrate drinks (CHO). A 4-km run-test with 20 control points was performed before and on the last day of the intervention. Blood and saliva were obtained in the mornings, before and after run-tests, and after the last training session. During the intervention, questionnaires were fulfilled regarding psychological sense of performance capacity and motivation. PRO-CHO and not CHO improved performance in the 4-km run-test (interaction p < .05). An increase in serum creatine kinase was observed during the week, which was greater in CHO than PRO-CHO (interaction p < .01). Lactate dehydrogenase (p < .001) and cortisol (p = .057) increased during the week, but the change did not differ between groups. Reduction in sense of performance capacity during the intervention was greater in CHO (p < .05) than PRO-CHO. In conclusion, ingestion of whey protein hydrolysate before and after each exercise session improves performance and reduces markers of muscle damage during a strenuous 1-week training camp. The results indicate that protein supplementation in conjunction with each exercise session facilitates the recovery from strenuous training in elite orienteers.

The purpose of this study was to examine whether speed endurance training (SET, repeated 30-s sprints) and heavy resistance training (HRT, 80-90% of 1 repetition maximum) performed in succession are compatible and lead to performance improvements in moderately trained endurance runners. For an 8-wk intervention period (INT) 23 male runners [maximum oxygen uptake (V̇O(2max)) 59 ± 1 ml·min(-1)·kg(-1); values are means ± SE] either maintained their training (CON, n = 11) or performed high-intensity concurrent training (HICT, n = 12) consisting of two weekly sessions of SET followed by HRT and two weekly sessions of aerobic training with an average reduction in running distance of 42%. After 4 wk of HICT, performance was improved (P < 0.05) in a 10-km run (42:30 ± 1:07 vs. 44:11 ± 1:08 min:s) with no further improvement during the last 4 wk. Performance in a 1,500-m run (5:10 ± 0:05 vs. 5:27 ± 0:08 min:s) and in the Yo-Yo IR2 test (706 ± 97 vs. 491 ± 65 m) improved (P < 0.001) only following 8 wk of INT. In HICT, running economy (189 ± 4 vs. 195 ± 4 ml·kg(-1)·km(-1)), muscle content of NHE1 (35%) and dynamic muscle strength was augmented (P < 0.01) after compared with before INT, whereas V̇O(2max), muscle morphology, capillarization, content of muscle Na(+)/K(+) pump subunits, and MCT4 were unaltered. No changes were observed in CON. The present study demonstrates that SET and HRT, when performed in succession, lead to improvements in both short- and long-term running performance together with improved running economy as well as increased dynamic muscle strength and capacity for muscular H(+) transport in moderately trained endurance runners., (Copyright © 2014 the American Physiological Society.)

We evaluated the physiological response, sprint performance and technical ability in various phases of the Copenhagen Soccer Test for Women (CSTw) and investigated whether the locomotor activities of the CSTw were comparable to competitive match-play (CM). Physiological measurements and physical/technical assessments were performed during CSTw for eleven Norwegian high-level women soccer players. The activity pattern during CSTw and CM was monitored using the ZXY tracking system. No differences were observed between CSTw and CM with regards to total distance covered (10093±94 and 9674±191m), high intensity running (1278±67 and 1193±115m) or sprinting (422±55 and 372±46m) (p>.05). During CSTw, average HR was 85±2%HRmax with 35±2% playing time >90%HRmax. Blood lactate increased (p<.05) from 1.4±0.3mM at rest to an average of 4.7±0.5mM during CSTw, with no changes during the test. Blood glucose was 5.4±0.3mM at rest and remained unaltered during CSTw. Sprint performance (2×20m) decreased (p<.05) by 3% during CSTw (8.19±0.06-8.47±0.10s). In conclusion, the locomotor activities during CSTw were comparable to that of high-level competitive match-play. The physiological demands of the CSTw were high, with no changes in heart rate, blood lactate or technical performance during the test, but a lowered sprint performance towards the end of the test., (Copyright © 2013 Elsevier B.V. All rights reserved.)

Purpose: The present study examined the effect of additional speed endurance training (SET) during the season on muscle adaptations and performance of trained soccer players., Methods: Eighteen subelite soccer players performed one session with six to nine 30-s intervals at an intensity of 90%-95% of maximal intensity (SET) a week for 5 wk (SET intervention). Before and after the SET intervention, the players carried out the Yo-Yo intermittent recovery level 2 (Yo-Yo IR2) test, a sprint test (10 and 30 m), and an agility test. In addition, seven of the players had a resting muscle biopsy specimen taken and they carried out a running protocol on a motorized treadmill before and after the SET intervention., Results: After the SET intervention, the Yo-Yo IR2 test (n = 13) performance was 11% better (P < 0.05), whereas sprint (n = 15) and agility (n = 13) performances were unchanged. The expression of the monocarboxylate transporter 1 (n = 6) was 9% higher (P < 0.05). and the expression of the Na(+)/K(+) pump subunit β(1) (n = 6) was 13% lower (P < 0.05) after the SET intervention. The Na(+)/K(+) pump subunits α(1), α(2), as well as the monocarboxylate transporter 4 and the Na(+)/H(+) exchanger 1 (n = 6) were unchanged. After the SET intervention, the relative number of Type IIx fibers and oxygen consumption at 10 km.h(-1) were lower (P < 0.05), whereas VO(2max) was unchanged., Conclusions: In conclusion, adding ∼30 min of SET once a week during the season for trained soccer players did lead to an improved ability to perform repeated high-intensity exercise, with a concomitant increase in the expression of monocarboxylate transporter 1 and an improved running economy.

The effect of an alteration from regular endurance to interval (10-20-30) training on the health profile, muscular adaptations, maximum oxygen uptake (Vo(2max)), and performance of runners was examined. Eighteen moderately trained individuals (6 females and 12 males; Vo(2max): 52.2 ± 1.5 ml·kg(-1)·min(-1)) (means ± SE) were divided into a high-intensity training (10-20-30; 3 women and 7 men) and a control (CON; 3 women and 5 men) group. For a 7-wk intervention period the 10-20-30 replaced all training sessions with 10-20-30 training consisting of low-, moderate-, and high-speed running (<30%, <60%, and >90% of maximal intensity) for 30, 20, and 10 s, respectively, in three or four 5-min intervals interspersed by 2 min of recovery, reducing training volume by 54% (14.0 ± 0.9 vs. 30.4 ± 2.3 km/wk) while CON continued the normal training. After the intervention period Vo(2max) in 10-20-30 was 4% higher, and performance in a 1,500-m and a 5-km run improved (P < 0.05) by 21 and 48 s, respectively. In 10-20-30, systolic blood pressure was reduced (P < 0.05) by 5 ± 2 mmHg, and total and low-density lipoprotein (LDL) cholesterol was lowered (P < 0.05) by 0.5 ± 0.2 and 0.4 ± 0.1 mmol/l, respectively. No alterations were observed in CON. Muscle membrane proteins and enzyme activity did not change in either of the groups. The present study shows that interval training with short 10-s near-maximal bouts can improve performance and Vo(2max) despite a ∼50% reduction in training volume. In addition, the 10-20-30 training regime lowers resting systolic blood pressure and blood cholesterol, suggesting a beneficial effect on the health profile of already trained individuals.

The present study examined the effect of football (F, n=15) training on the health profile of habitually active 25-45-year-old men with mild hypertension and compared it with running (R, n=15) training and no additional activity (controls, C, n=17). The participants in F and R completed a 1-h training session 2.4 times/week for 12 weeks. Systolic and diastolic blood pressure decreased in all groups but the decrease in diastolic blood pressure in F (-9 +/- 5 (+/- SD) mmHg) was higher than that in C (-4 +/- 6 mmHg). F was as effective as R in decreasing body mass (-1.6 +/- 1.8 vs-1.5 +/- 2.1 kg) and total fat mass (-2.0 +/- 1.5 vs -1.6 +/- 1.5 kg) and in increasing supine heart rate variability, whereas no changes were detected for C. Maximal stroke volume improved in F (+13.1%) as well as in R (+10.1%) compared with C (-4.9%). Total cholesterol decreased in F (5.8 +/- 1.2 to 5.5 +/- 0.9 mmol/L) but was not altered in R and C. We conclude that football training, consisting of high-intensity intermittent exercise, results in positive effects on blood pressure, body composition, stroke volume and supine heart rate variability, and elicits at least the same cardiovascular health benefits as continuous running exercise in habitually active men with mild hypertension.

We examined long-term musculoskeletal and cardiac adaptations elicited by recreational football (FG, n=9) and running (RG, n=10) in untrained premenopausal women in comparison with a control group (CG, n=9). Training was performed for 16 months ( approximately 2 weekly 1-h sessions). For FG, right and left ventricular end-diastolic diameters were increased by 24% and 5% (P<0.05), respectively, after 16 months. Right ventricular systolic function measured by tricuspid annular plane systolic excursion (TAPSE) increased (P<0.05) in FG after 4 months and further (P<0.05) after 16 months (15% and 32%, respectively). In RG and CG, cardiac structure, E/A and TAPSE remained unchanged. For FG, whole-body bone mineral density (BMD) was 2.3% and 1.3% higher (P<0.05) after 16 months, than after 4 and 0 months, respectively, with no changes for RG and CG. FG demonstrated substantial improvements (P<0.05) in fast (27% and 16%) and slow (16% and 17%) eccentric muscle strength and rapid force capacity (Imp30ms: 66% and 65%) after 16 months compared with 4 and 0 months, with RG improving Imp30ms by 64% and 46%. In conclusion, long-term recreational football improved muscle function, postural balance and BMD in adult women with a potential favorable influence on the risk of falls and fractures. Moreover, football training induced consistent cardiac adaptations, which may have implications for long-term cardiovascular health.

We studied the effect of an alteration from regular endurance to speed endurance training on muscle oxidative capacity, capillarization, as well as energy expenditure during submaximal exercise and its relationship to mitochondrial uncoupling protein 3 (UCP3) in humans. Seventeen endurance-trained runners were assigned to either a speed endurance training (SET; n = 9) or a control (Con; n = 8) group. For a 4-wk intervention (IT) period, SET replaced the ordinary training ( approximately 45 km/wk) with frequent high-intensity sessions each consisting of 8-12 30-s sprint runs separated by 3 min of rest (5.7 +/- 0.1 km/wk) with additional 9.9 +/- 0.3 km/wk at low running speed, whereas Con continued the endurance training. After the IT period, oxygen uptake was 6.6, 7.6, 5.7, and 6.4% lower (P < 0.05) at running speeds of 11, 13, 14.5, and 16 km/h, respectively, in SET, whereas remained the same in Con. No changes in blood lactate during submaximal running were observed. After the IT period, the protein expression of skeletal muscle UCP3 tended to be higher in SET (34 +/- 6 vs. 47 +/- 7 arbitrary units; P = 0.06). Activity of muscle citrate synthase and 3-hydroxyacyl-CoA dehydrogenase, as well as maximal oxygen uptake and 10-km performance time, remained unaltered in both groups. In SET, the capillary-to-fiber ratio was the same before and after the IT period. The present study showed that speed endurance training reduces energy expenditure during submaximal exercise, which is not mediated by lowered mitochondrial UCP3 expression. Furthermore, speed endurance training can maintain muscle oxidative capacity, capillarization, and endurance performance in already trained individuals despite significant reduction in the amount of training.

Purpose: To examine muscle and blood metabolites during soccer match play and relate it to possible changes in sprint performance., Methods: Thirty-one Danish fourth division players took part in three friendly games. Blood samples were collected frequently during the game, and muscle biopsies were taken before and after the game as well as immediately after an intense period in each half. The players performed five 30-m sprints interspersed by 25-s recovery periods before the game and immediately after each half (N=11) or after an intense exercise period in each half (N=20)., Results: Muscle lactate was 15.9+/-1.9 and 16.9+/-2.3 mmol.kg d.w. during the first and second halves, respectively, with blood lactate being 6.0+/-0.4 and 5.0+/-0.4 mM, respectively. Muscle lactate was not correlated with blood lactate (r=0.06-0.25, P>0.05). Muscle glycogen decreased (P<0.05) from 449+/-23 to 255+/-22 mmol.kg d.w. during the game, with 47+/-7% of the muscle fibers being completely or almost empty of glycogen after the game. Blood glucose remained elevated during the game, whereas plasma FFA increased (P<0.05) from 0.45+/-0.05 to 1.37+/-0.23 mM. Mean sprint time was unaltered after the first half, but longer (P<0.05) after the game (2.8+/-0.7%) as well as after intense periods in the first (1.6+/-0.6%) and second halves (3.6+/-0.5%). The decline in sprint performance during the game was not correlated with muscle lactate, muscle pH, or total glycogen content., Conclusion: Sprint performance is reduced both temporarily during a game and at the end of a soccer game. The latter finding may be explained by low glycogen levels in individual muscle fibers. Blood lactate is a poor indicator of muscle lactate during soccer match play.

Purpose: To examine the activity profile and physical loading of elite female soccer players during match play and to study the relationship between training status and physical match performance., Methods: Time-motion analysis and HR recordings were performed on 14 elite female soccer players during competitive matches. In addition, the players carried out a laboratory treadmill test and the Yo-Yo intermittent recovery test., Results: The total distance covered during a game was 10.3 km (range: 9.7-11.3) with high-intensity running (HIR) accounting for 1.31 km (0.71-1.70). HIR was performed 125 times (72-159) for 2.3 s (2.0-2.4) on average. The average and peak HR in a game were 167 beats per minute (bpm) (152-186) and 186 (171-205), respectively, corresponding to 87% (81-93) and 97% (96-100) of HR(max). Maximal pulmonary oxygen uptake (VO2max) was 49.4 mL.min(-1).kg(-1) (43.4-56.8), and incremental treadmill test (ITT) performance was 4.49 min (3.38-5.17). The Yo-Yo test performance was 1379 m (600-1960). The total distance covered during match play did not correlate with VO2max or ITT performance but correlated with the Yo-Yo test result (r = 0.56, P < 0.05). Significant positive correlations were observed between HIR and VO2max (r = 0.81, P < 0.05), ITT (r = 0.82, P < 0.05), and Yo-Yo test performance (r = 0.76, P < 0.05). No relationship was observed between HR(max) during match play and any of the performance measures., Conclusion: The present study demonstrated that 1) HIR during games varies markedly between elite female soccer players, 2) all players have high HR throughout a competitive game with periods of near-maximal values, 3) the distance covered by HIR during match play is closely related to the physical capacity, and 4) the Yo-Yo intermittent recovery test can be used as an indicator of the physical match performance of elite female players.

To determine the movement patterns and physiological demands of top-class soccer assistant referees, we performed computerized time-motion analysis and measured heart rate and blood lactate concentration in 15 assistant referees during 22 competitive matches in the top Danish league. To relate match performance to the physical capability of the assistant referees, they performed a 3 x 30 m sprint protocol before and after matches and a laboratory treadmill test within 3 weeks of the games. The mean total distance covered by the top-class assistant referees was 7.28 (range 5.78-8.16) km, of which 1.15 (0.86-1.44) km was high-intensity running and 1.16 (0.12-2.34) km was sideways running. The amount of high-intensity running during a game was correlated with performance of repeated sprints (r = 0.80, P < 0.05). Mean heart rate was 137 (117-159) beats x min(-1), corresponding to 73% (60-88%) of maximal heart rate and 65% (53-80%) of maximal oxygen uptake. Blood lactate concentration was 4.7 (1.6-11.0) and 4.8 (1.1-13.7) mmol x 1(-1) after the first and second half, respectively. Sprinting performance was poorer (P < 0.05) after than before the games. The peak distance to the offside line was greater (P < 0.05) in the second than the first half (7 +/- 1 vs 5 +/- 0 m). Our results show that: (1) top-class assistant soccer refereeing is characterized by brief intense bouts of forward and sideways running interspersed with long periods of low activity; (2) top-class soccer assistant referees have moderate aerobic energy production during games with episodes of high aerobic and anaerobic energy turnover; (3) assistant referees' performance of repeated sprints correlates with the amount of high-intensity running performed in a game; and (4) sprint performance decreases towards the end of a game, which appears to affect assistant referees' ability to keep up with play.

The aim of this study was to characterize Kenyan runners in regard to their oxygen uptake and blood and ammonia responses when running. Untrained Kenyan boys (14.2 +/- 0.2 years) and Scandinavian runners were included for comparison. The studies were performed at altitude (approximately 2.000 m.a.s.l.) and, for several Kenyan and Scandinavian runners, at sea level as well. At altitude sedentary adolescent Kenyan boys had a mean maximal oxygen uptake (VO2max) of 47 (44-51) ml.kg-1.min-1, whereas similarly aged boys regularly walking or running but not training for competition reached above 62 (58-71) ml.kg-1.min-1 in VO2max. Kenyan runners in active training had 68 +/- 1.4 ml.kg-1.min-1 at altitude and 79.9 +/- 1.4 ml.kg-1.min-1 at sea level, with individuals reaching 85 ml.kg-1.min-1. The best Scandinavian runners were not significantly different from the Kenyan runners in VO2max both at altitude and at sea level, but none of the Scandinavians reached as high individual values as observed for some Kenyan runners. The running efficiency, determined as the oxygen cost at a given running speed, was less in the Kenyan runners, and the difference became more pronounced when body weight was expressed in ml.kg-0.75 min-1. Blood lactate concentration was in general lower in the Kenyan than in the Scandinavian runners, and the Kenyans also had extremely low ammonia accumulation in the blood even at very high exercise intensities. It is concluded that it is the physical activity during childhood, combined with intense training as teenagers that brings about the high VO2max observed in some Kenyan runners. Their high aerobic capacity, as well as their good running economy, makes them such superior runners. In addition, their low blood lactate and ammonia accumulation in blood when running may also be contributing factors.

Anthropometric characteristics, physical fitness and technical skills of under-19 (U19) soccer players were compared by competitive level (elite, n = 95; non-elite, n = 85) and playing position (goalkeeper, central defender, fullback, midfield, forward). Fitness tests included 5- and 30-m sprints, agility, squat jump (SJ) and countermovement jump (CMJ), strength and Yo-Yo intermittent endurance test level 2 (Yo-Yo IE2). Soccer-specific skills included ball control and dribbling. Independent of position, elite players presented more hours of training per year than non-elite players ( d > 1.2). Stature and body mass discriminated elite from non-elite players among goalkeepers and central defenders ( d > 0.6). Major differences were noted between elite and non-elite goalkeepers for SJ, CMJ, Yo-Yo IE2, and ball control ( d > 1.2). Elite central defenders performed better than their non-elite counterparts in SJ and ball control tests ( d > 1.2). Elite players presented better agility and Yo-Yo IE2 performances than non-elite players within all positional roles ( d > 0.6). In conclusion, U19 players differed in anthropometric characteristics, physical fitness and technical skills by competitive level within field positions. [ABSTRACT FROM AUTHOR]

The aims of this study were to (1) determine the reproducibility of sub-maximal and maximal versions of the Yo-Yo intermittent endurance test level 2 (Yo-Yo IE2 test), (2) assess the relationship between the Yo-Yo IE2 test and match performance and (3) quantify the sensitivity of the Yo-Yo IE2 test to detect test-retest changes and discriminate between performance for different playing standards and positions in elite soccer. Elite (n = 148) and sub-elite male (n = 14) soccer players carried out the Yo-Yo IE2 test on several occasions over consecutive seasons. Test-retest coefficient of variation (CV) in Yo-Yo IE2 test performance and heart rate after 6 min were 3.9% (n = 37) and 1.4% (n = 32), respectively. Elite male senior and youth U19 players Yo-Yo IE2 performances were better (P < 0.01) than elite youth U16s and sub-elite players (2,603 ± 451 and 2,534 ± 549 vs. 1,855 ± 535 vs. 1,749 ± 382 m). The intra- and inter-season CV for Yo-Yo IE2 test performance were 4.2 and 5.6%, respectively. A correlation was observed (P < 0.05) between Yo-Yo IE2 test performance and the total (r = 0.74) and high-intensity (r = 0.58) running distance covered in a match. A correlation was also evident (P < 0.01) between Yo-Yo IE2 test heart rate after 6 min expressed in percentage of maximal heart rate and the peak values for high-intensity running performed by midfielders in 5-min (r = -0.71), 15-min (r = -0.75) and 45-min periods (r = -0.77). The present data demonstrate that the Yo-Yo IE2 test is reproducible and can be used to determine the capacity of elite soccer players to perform intense intermittent exercise. Furthermore, the Yo-Yo IE2 test was shown to be a sensitive tool that not only relates to match performance but can also differentiate between intermittent exercise performance of players in various standards, stages of the season and playing positions. [ABSTRACT FROM AUTHOR]

The present study examined the cardiovascular health effects of 16 weeks of recreational football training in untrained premenopausal women in comparison with continuous running training. Fifty healthy women were matched and randomized to a football (FG, n=25) or a running (RG, n=25) group and compared with a control group with no physical training (CO, n=15). Training was performed for 1 h twice a week. After 16 weeks, systolic and diastolic blood pressure was reduced ( P<0.05) in FG (7±2 and 4±1 mmHg) and systolic blood pressure was lowered ( P<0.05) in RG (6±2 mmHg). After 16 weeks, resting heart rate was lowered ( P<0.05) by 5±1 bpm both in FG and RG, and maximal oxygen uptake was elevated ( P<0.05) by 15% in FG and by 10% in RG (5.0±0.7 and 3.6±0.6 mL/min/kg, respectively). Total fat mass decreased ( P<0.05) by 1.4±0.3 kg in FG and by 1.1±0.3 kg in RG. After 16 weeks, pulse pressure wave augmentation index (−0.9±2.5 vs 4.2±2.4%), skeletal muscle capillarization (2.44±0.15 vs 2.07±0.05 cap/fib) and low-density lipoprotein/high-density lipoprotein cholesterol ratio were improved ( P<0.05) in FG, but not altered in RG. No changes were observed in CO. In conclusion, regular recreational football training has significant favorable effects on the cardiovascular risk profile in untrained premenopausal women and is at the least as efficient as continuous running. [ABSTRACT FROM AUTHOR]