***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: The aim of this study was to investigate the effects of very high intensity sprint interval training ( SIT ) on metabolic and vascular risk factors in overweight/obese sedentary men . Ten men ( age , 32.1 ± 8.7 years ; body mass index , 31.0 ± 3.7 kg m(-2 ) ) participated . After baseline metabolic , anthropometric , and fitness measurements , participants completed a 2-week SIT intervention , comprising 6 sessions of 4 to 6 repeats of 30-second Wingate anaerobic sprints on an electromagnetically braked cycle ergometer , with 4.5-minute recovery between each repetition . Metabolic , anthropometric , and fitness assessment s were repeated post-intervention . Both maximal oxygen uptake ( 2.98 ± 0.15 vs 3.23 ± 0.14 L min(-1 ) , P = .013 ) and mean Wingate power ( 579 ± 24 vs 600 ± 19 W , P = .040 ) significantly increased after 2 weeks of  SIT . Insulin sensitivity index ( 5.35 ± 0.72 vs 4.34 ± 0.72 , P = .027 ) and resting fat oxidation rate in the fasted state ( 0.13 ± 0.01 vs 0.11 ± 0.01 g min(-1 ) , P = .019 ) were significantly higher and systolic blood pressure ( 121 ± 3 vs 127 ± 3 mm Hg , P = .020 ) and resting carbohydrate oxidation in the fasted state ( 0.03 ± 0.01 vs 0.08 ± 0.02 g min(-1 ) , P = .037 ) were significantly lower 24 hours post-intervention compared with baseline , but these changes were no longer significant 72 hours post-intervention . Significant decreases in waist ( 98.9 ± 3.1 vs 101.3 ± 2.7 cm , P = .004 ) and hip ( 109.8 ± 2.2 vs 110.9 ± 2.2 cm , P = .017 ) circumferences compared with baseline were also observed after the intervention . Thus , 2 weeks of SIT substantially improved a number of metabolic and vascular risk factors in overweight/obese sedentary men , highlighting the potential for this to provide an alternative exercise model for the improvement of vascular and metabolic health in this population Low-volume sprint interval training ( SIT ) , or repeated sessions of brief , intense intermittent exercise , elicits metabolic adaptations that resemble traditional high-volume endurance training ( ET ) . The effects of these different forms of exercise training on vascular structure and function remain largely unexplored . To test the hypothesis that SIT and ET would similarly improve peripheral artery distensibility and endothelial function and central artery distensibility , we recruited 20 healthy untrained subjects ( age : 23.3 + /- 2.8 yr ) and had them perform 6 wk of SIT or ET ( n = 5 men and 5 women per group ) . The SIT group completed four to six 30-s " all-out " Wingate tests separated by 4.5 min of recovery 3 days/wk . The ET group completed 40 - 60 min of cycling at 65 % of their peak oxygen uptake ( Vo2peak ) 5 days/wk . Popliteal endothelial function , both relative and normalized to shear stimulus , was improved after training in both groups ( main effect for time , P < 0.05 ) . Carotid artery distensibility was not statistically altered by training ( P = 0.29 ) in either group ; however , popliteal artery distensibility was improved in both groups to the same degree ( main effect , P < 0.05 ) . We conclude that SIT is a time-efficient strategy to elicit improvements in peripheral vascular structure and function that are comparable to ET . However , alterations in central artery distensibility may require a longer training stimuli and /or greater initial vascular stiffness than observed in this group of healthy subjects Our purpose was to examine the effects of sprint interval training on muscle glycolytic and oxidative enzyme activity and exercise performance .  Twelve healthy men ( 22 + /- 2 yr of age ) underwent intense interval training on a cycle ergometer for 7 wk . Training consisted of 30-s maximum sprint efforts ( Wingate protocol ) interspersed by 2 - 4 min of recovery , performed three times per week . The program began with four intervals with 4 min of recovery per session in week 1 and progressed to 10 intervals with 2.5 min of recovery per session by week 7 . Peak power output and total work over repeated maximal 30-s efforts and maximal oxygen consumption ( VO2 max ) were measured before and after the training program . Needle biopsies were taken from vastus lateralis of nine subjects before and after the program and assayed for the maximal activity of hexokinase , total glycogen phosphorylase , phosphofructokinase , lactate dehydrogenase , citrate synthase , succinate dehydrogenase , malate dehydrogenase , and 3-hydroxyacyl-CoA dehydrogenase . The training program result ed in significant increases in peak power output , total work over 30 s , and VO2 max . Maximal enzyme activity of hexokinase , phosphofructokinase , citrate synthase , succinate dehydrogenase , and malate dehydrogenase was also significantly ( P < 0.05 ) higher after training . It was concluded that relatively brief but intense sprint training can result in an increase in both glycolytic and oxidative enzyme activity , maximum short-term power output , and VO2 max Adaptations in fat and carbohydrates metabolism after a prolonged endurance training program were examined using stable isotope tracers of glucose ( [6,6 - 2H2]glucose ) , glycerol ( [2H5]glycerol ) , and palmitate ( [2H2]palmitate ) . Active , but untrained , males  exercised on a cycle for 2 h/day [ 60 % pretraining peak O2 consumption ( VO2peak ) = 44.3 + /- 2.4 ml.kg-1.min-1 ] for a total of 31 days . Three cycle tests ( 90 min at 60 % pretraining VO2peak ) were administered before training ( PRE ) and after 5 ( 5D ) and 31 ( 31D ) days of training . Exercise increased the rate of glucose production ( Ra ) and utilization ( Rd ) as well as the rate of lipolysis ( glycerol Ra ) and free fatty acid turnover ( FFARa/Rd ) . At 5D , training induced a 10 % ( P < 0.05 ) increase in total fat oxidation because of an increase in intramuscular triglyceride oxidation ( + 63 % , P < 0.05 ) and a decreased glycogen oxidation ( -16 % , P < 0.05 ) . At 31D , total fat oxidation during exercise increased a further 58 % ( P < 0.01 ) . The pattern of fat utilization during exercise at 31D showed a reduced reliance on plasma FFA oxidation ( FFA Rd ) and a greater dependence on oxidation of intramuscular triglyceride , which increased more than twofold ( P < 0.001 ) . In addition , glucose Ra and Rd were reduced at all time points during exercise at 31D compared with PRE and 5D . We conclude that long-term training induces a progressive increase in fat utilization mediated by a greater oxidation of fats from intramuscular sources and a reduction in glucose oxidation . Initial changes are present as early as 5D and occur before increases in muscle maximal mitochondrial enzyme activity UNLABELLED Repeated maximal-intensity short- duration exercise ( sprint interval training , SIT ) can produce muscle adaptations similar to endurance training ( ET ) despite a much reduced training volume . However , most SIT data use cycling , and little is known about its effects on body composition or maximal cardiac output ( Qmax ) . PURPOSE The purpose of this study was to assess body composition , 2000-m run time trial , VO(2max ) , and Q(max ) effects of run SIT versus ET . METHODS Men and women ( n = 10 per group ; mean ± SD : age = 24 ± 3 yr ) trained three times per week for  6 wk with SIT , 30-s all-out run sprints ( manually driven treadmill ) , four to six bouts per session , 4-min recovery per bout , versus ET , 65 % VO(2max ) for 30 to 60 min·d(-1 ) . RESULTS Training improved ( P < 0.05 ) body composition , 2000-m run time trial performance , and VO(2max ) in both groups . Fat mass decreased 12.4 % with SIT ( mean ± SEM ; 13.7 ± 1.6 to 12.0 ± 1.6 kg ) and 5.8 % with ET ( 13.9 ± 1.7 to 13.1 ± 1.6 kg ) . Lean mass increased 1 % in both groups . Time trial performance improved 4.6 % with SIT ( -25.6 ± 8.1 s ) and 5.9 % with ET ( -31.9 ± 6.3 s ) . VO(2max ) increased 11.5 % with SIT ( 46.8 ± 1.6 to 52.2 ± 2.0 mL·kg·(-1)·min(-1 ) ) and 12.5 % with ET ( 44.0 ± 2.0 to 49.5 ± 2.6 mL·kg·(-1)·min(-1 ) ) . None of these improvements differed between groups . In contrast , Q(max ) increased by 9.5 % with ET only ( 22.2 ± 2.0 to 24.3 ± 1.6 L·min(-1 ) ) . CONCLUSIONS Despite a fraction of the time commitment , run SIT induces similar body composition , VO(2max ) , and performance adaptations as ET , but with no effect on Q(max ) . These data suggest that adaptations with ET are of central origin primarily , whereas those with SIT are more Parra et al. ( Acta Physiol . Sc and 169 : 157 - 165 , 2000 ) showed that 2 wk of daily sprint interval training ( SIT ) increased citrate synthase ( CS ) maximal activity but did not change " anaerobic " work capacity , possibly because of chronic fatigue induced by daily training . The effect of fewer SIT sessions on muscle oxidative potential is unknown , and aside from changes in peak oxygen uptake ( Vo(2 peak ) ) , no study has examined the effect of SIT on " aerobic " exercise capacity . We tested the hypothesis that six sessions of SIT , performed over 2 wk with 1 - 2 days rest between sessions to promote recovery , would increase CS maximal activity and endurance capacity during cycling at approximately 80 % Vo(2 peak ) . Eight recreationally active subjects [ age = 22 + /- 1 yr ; Vo(2 peak ) = 45 + /- 3 ml.kg(-1).min(-1 ) ( mean + /- SE ) ] were studied before and 3 days after SIT . Each training session consisted of four to seven " all-out " 30-s Wingate tests with 4 min of recovery . After SIT , CS maximal activity increased by 38 % ( 5.5 + /- 1.0 vs. 4.0 + /- 0.7 mmol.kg protein(-1).h(-1 ) ) and resting muscle glycogen content increased by 26 % ( 614 + /- 39 vs. 489 + /- 57 mmol/kg dry wt ) ( both P < 0.05 ) . Most strikingly , cycle endurance capacity increased by 100 % after SIT ( 51 + /- 11 vs. 26 + /- 5 min ; P < 0.05 ) , despite no change in Vo(2 peak ) . The coefficient of variation for the cycle test was 12.0 % , and a control group ( n = 8) showed no change in performance when tested approximately 2 wk apart without SIT . We conclude that short sprint interval training ( approximately 15 min of intense exercise over 2 wk ) increased muscle oxidative potential and doubled endurance capacity during intense aerobic cycling in recreationally active individuals The insulin resistance of skeletal muscle in glucose-tolerant obese individuals is associated with reduced activity of oxidative enzymes and a disproportionate increase in activity of glycolytic enzymes . Because non-insulin-dependent diabetes mellitus ( NIDDM ) is a disorder characterized by even more severe insulin resistance of skeletal muscle and because many individuals with NIDDM are obese , the present study was undertaken to examine whether decreased oxidative and increased glycolytic enzyme activities are also present in NIDDM .  Percutaneous biopsy of vatus lateralis muscle  was obtained in eight lean ( L ) and eight obese ( O ) nondiabetic subjects and in eight obese NIDDM subjects and was assayed for marker enzymes of the glycolytic [ phosphofructokinase , glyceraldehyde phosphate dehydrogenase , hexokinase ( HK ) ] and oxidative pathways [ citrate synthase ( CS ) , cytochrome-c oxidase ] , as well as for a gly 
    Output:
    
Strong evidence support improvements of aerobic exercise performance and VO2max following SIT .
Solid evidence support peripheral adaptations known to increase the oxidative potential of the muscle following SIT , whereas evidence regarding central adaptations was limited and equivocal .
Some evidence indicated changes in substrate oxidation at rest and during exercise as well as improved glycemic control and insulin sensitivity following SIT .
In conclusion , strong evidence support improvement of aerobic exercise performance and VO2max following SIT , which coincides with peripheral muscular adaptations .