***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 distinction between positive and negative training adaptation is an important prerequisite in the identification of any marker for monitoring training in athletes . To investigate the glutamine responses to progressive endurance training , twenty healthy males were r and omly assigned to a training group or a non-exercising control group . The training group performed a progressive ( 3 to 6 x 90 minute sessions per week at 70 % V.O ( 2max ) ) six-week endurance training programme on a cycle ergometer , while the control group did not participate in any exercise during this period .  Performance assessment s ( V.O ( 2max ) and time to exhaustion ) and resting blood sample s ( for haemoglobin concentration , haematocrit , cortisol , ferritin , creatine kinase , glutamine , uric acid and urea analysis ) were obtained prior to the commencement of training ( Pre ) and at the end of week 2 , week 4 and week 6 . The training group showed significant improvements in time to exhaustion ( p < 0.01 ) , and V.O ( 2max ) ( p < 0.05 ) at all time points ( except week 2 for V.O ( 2max ) ) , while the control group performance measures did not change . In the training group , haemoglobin concentration and haematocrit were significantly lower ( p < 0.01 ) than pretraining values at week 2 and 4 , as percentage changes in plasma volume indicated a significant ( p < 0.01 ) haemodilution ( + 6 - 9 % ) was present at week 2 , 4 and 6 . No changes were seen in the control group . In the training group , plasma glutamine ( week 2 , 4 and 6 ) , creatine kinase ( week 2 and 4 ) , uric acid ( week 2 and 4 ) and urea ( week 2 and 4 ) all increased significantly from pretraining levels . No changes in cortisol or ferritin were found in the training group and no changes in any blood variables were present in the control group . Plasma glutamine was the only blood variable to remain significantly above pretraining ( 966 + /- 32 micromol . 1 ( -1 ) ) levels at week 6 ( 1176 + /- 24 micromol . 1 ( -1 ) ; p < 0.05 ) The elevation seen here in glutamine levels , after 6 weeks of progressive endurance training , is in contrast to previous reports of decreased glutamine concentrations in overtrained athletes . In conclusion , 6 weeks of progressive endurance training steadily increased plasma glutamine levels , which may prove useful in the monitoring of training responses Eleven men sprint trained  two to three times per week for 6 wk to investigate possible exercise-induced slow-to-fast fiber type conversions . Six individuals served as controls . Both groups were tested at the beginning and end of the study to determine anaerobic performance and maximal oxygen consumption . In addition , pre- and postbiopsies were extracted from the vastus lateralis muscle and were analyzed for fiber type composition , cross-sectional area , and myosin heavy chain ( MHC ) content . No significant changes were found in anaerobic or aerobic performance variables for either group . Although a trend was found for a decrease in the percentage of type IIb fibers , high-intensity sprint cycle training caused no significant changes in the fiber type distribution or cross-sectional area . However , the training protocol did result in a significant decrease in MHC IIb with a concomitant increase in MHC IIa for the training men . These data appear to support previous investigations that have suggested exercise-induced adaptations within the fast fiber population ( IIb-->IIa ) after various types of training ( endurance and strength ) BACKGROUND Recently , there has been an increase in popularity and participation in the sport of  snowshoeing . While the sport has gained considerable recognition , to date there is little or no scientific research regarding training responses to snowshoeing as a form of exercise . Therefore , the purpose of this study was to determine whether snowshoe training could improve fitness measures . A further purpose was to compare responses from a snowshoe training program to a similarly design ed run training program . METHODS This prospect i ve , comparative study was conducted with healthy males and females between the ages of 19 and 24 . These subjects were recruited from the University of Vermont population and surrounding community . Following baseline measurements in VO2max , running time to exhaustion ( RTE ) , and anthropometry , 17 subjects ( 10 snowshoers and 7 runners ) participated in a six week conditioning program . Both groups exercised for 30 min at 75 - 85 % age predicted maximum heart rate , 3 - 4 times per week , for a total of 18 sessions . RESULTS VO2max improved significantly in both running and snowshoeing groups , 6.3 and 8.5 % , respectively . Run time to exhaustion also improved significantly in both groups , 23.3 and 33.5 % , respectively . There were no changes in anthropometry for either group . With the exception of RTE , there were no statistically significant differences between groups in any other measurements at baseline . CONCLUSIONS These results support the acceptability of snowshoeing as a valid means to improve or maintain cardiovascular endurance 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 PURPOSE To determine whether various intensities of aerobic training differentially affect aerobic capacity as well as resting HR and resting blood pressure ( BP ) . METHODS Sixty-one health young adult subjects were matched for sex and VO2max and were r and omly assigned to a moderate- ( 50 % VO2 reserve ( VO2R ) , vigorous ( 75 % VO2R ) , near-maximal-intensity ( 95 % VO2R ) , or a nonexercising control group . Intensity during exercise was controlled by having the subjects maintain target HR based on HR reserve . Exercise volume ( and thus energy expenditure ) was controlled across the three training groups by varying duration and frequency . Fifty-five subjects completed a 6-wk training protocol on a stationary bicycle ergometer and pre- and posttesting . During the final 4 wk , the moderate-intensity group exercised for 60 min , 4 d.wk the vigorous-intensity group exercised for 40 min , 4 d.wk and the near-maximal-intensity group exercised 3 d.wk performing 5 min at 75 % VO2R followed by five intervals of 5 min at 95 % VO2R and 5 min at 50 % VO2R . RESULTS VO2max significantly increased in all exercising groups by 7.2 , 4.8 , and 3.4 mL.min.kg in the near-maximal- , the vigorous- , and the moderate-intensity groups , respectively . Percent increases in the near-maximal- ( 20.6 % ) , the vigorous- ( 14.3 % ) , and the moderate-intensity ( 10.0 % ) groups were all significantly different from each other ( P < 0.05 ) . There were no significant changes in resting HR and BP in any group . CONCLUSION When volume of exercise is controlled , higher intensities of exercise are more effective for improving VO2max than lower intensities of exercise in healthy , young adults To determine whether high-intensity interval training ( HIT ) would increase respiratory muscle strength and expiratory flow rates more than endurance training ( ET ) , 15 physically active , healthy subjects ( untrained ) were r and omly assigned to an ET group ( n = 7 ) or a HIT group ( n = 8) . All subjects performed an incremental test to exhaustion ( VO2max ) on a cycle ergometer before and after training . St and ard pulmonary function tests , maximum inspiratory pressure ( PImax ) , maximum expiratory pressure ( PEmax ) , and maximal flow volume loops were performed pre training and after each week of training . HIT subjects performed a 4-week training program , 3 days a week , on a cycle ergometer at 90 % of their VO2max final workload , while the ET subjects performed exercise at 60–70 % VO2max . The HIT group performed five 1-min bouts with 3-min recovery periods and the ET group cycled for 45 min continuously . A five-mile time trial ( TT ) was performed prior to , after 2 weeks , and after completion of training . Both groups showed improvements ( P < 0.05 ) in VO2max ( ~8–10 % ) and TT ( HIT 6.5 ± 1.3 % , ET 4.4 ± 1.8 % ) following training with no difference ( P > 0.05 ) between groups . Both groups increased ( P < 0.05 ) PImax post training ( ET ~ 25 % , HIT ~ 43 % ) with values significantly higher for HIT than ET . There was no change ( P > 0.05 ) in expiratory flow rates with training in either group . These data suggest that both whole-body exercise training and HIT are effective in increasing inspiratory muscle strength with HIT offering a time-efficient alternative to ET in improving aerobic capacity and performance PURPOSE The present study compared the effects of aerobic endurance training at different intensities and with different methods matched for total work and frequency . Responses in maximal oxygen uptake ( VO2max ) , stroke volume of the heart ( SV ) , blood volume , lactate threshold ( LT ) , and running economy ( CR ) were examined . METHODS Forty healthy , nonsmoking , moderately trained male subjects were r and omly assigned to one of four groups:1 ) long slow distance ( 70 % maximal heart rate ; HRmax ) ; 2)lactate threshold ( 85 % HRmax ) ; 3 ) 15/15 interval running ( 15 s of running at 90 - 95 % HRmax followed by 15 s of active resting at 70 % HRmax ) ; and 4 ) 4 x 4 min of interval running ( 4 min of running at 90 - 95 % HRmax followed by 3 min of active resting at 70%HRmax ) . All four training protocol s result ed in similar total oxygen consumption and were performed 3 d.wk for 8 wk . RESULTS High-intensity aerobic interval training result ed in significantly increased VO2max compared with long slow distance and lactate-threshold training intensities ( P<0.01 ) . The percentage increases for the 15/15 and 4 x 4 min groups were 5.5 and 7.2 % , respectively , reflecting increases in V O2max from 60.5 to 64.4 mL x kg(-1 ) x min(-1 ) and 55.5 to 60.4 mL x kg(-1 ) x min(-1 ) . SV increased significantly by approximately 10 % after interval training ( P<0.05 ) . CONCLUSIONS : High-aerobic intensity endurance interval training is significantly more effective than performing the same total work at either lactate threshold or at 70 % HRmax , in improving VO2max . The changes in VO2max correspond with changes in SV , indicating a close link between the two The aim of this longitudinal study was to compare two recovery modes ( active vs. passive ) during a seven-week  high-intensity interval training program  ( SWHITP ) aim ed to improve maximal oxygen uptake ( $ $ \dot{V}{\text{O } } _ { { 2 { \text{max } } } } $ $ ) , maximal aerobic velocity ( MAV ) , time to exhaustion ( tlim ) and time spent at a high percentage 
    Output:
    
There was no significant difference between tertiles in mean change in VO2max ( tertile 1:+0.29±0.15 l/min , ES ( effect size ) = 0.77 ; 2:+0.26±0.10 l/min , ES=0.68 ; 3:+0.35±0.17 l/min , ES=0.80 ) , despite significant ( p<0.05 ) reductions in session dose and total training volume as training intensity increased .
These data suggest that exercise training intensity has no effect on the magnitude of training-induced increases in maximal oxygen uptake in young healthy human participants , but similar adaptations can be achieved in low training doses at higher exercise intensities than higher training doses of lower intensity ( endurance training )