***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 purpose of this study was to compare changes in velocity-specific adaptations in moderately resistance-trained athletes who trained with either low or high resistances . The study used tests of sport-specific skills across an intermediate-to high-velocity spectrum . Thirty NCAA Division I baseball players were r and omly assigned to either a low-resistance ( 40–60 % 1 repetition maximum [ 1RM ] ) training group or a high-resistance ( 70–90 % 1RM ) training group . Both of the training groups intended to maximally accelerate each repetition during the concentric phase ( IMCA ) . The 10 weeks of training consisted of 4 training sessions a week using basic core exercises .  Peak force , velocity and power were evaluated during set angle and depth jumps as well as weighted jumps using 30 and 50 % 1RM .  Squat 1RMs  were also tested . Although no interactions for any of the jump tests were found , trends supported the hypothesis of velocity-specific training . Percentage gains suggest that the combined use of heavier training loads ( 70–90 % 1RM ) and IMCA tend to increase peak force in the lower-body leg and hip extensors . Trends also show that the combined use of lighter training loads ( 40–60 % 1RM ) and IMCA tend to increase peak power and peak velocity in the lower-body leg and hip extensors . The high-resistance group improved squats more than the low-resistance group ( p < 0.05 ; + 22.7 vs. + 16.1 kg ) . The results of this study support the use of a combination of heavier training loads and IMCA to increase 1RM strength in the lower bodies of resistance-trained athletes The purpose of the present study was to examine the influence of direct supervision on muscular strength , power , and running speed during 12 weeks of resistance training in young rugby league players . Two matched groups of young ( 16.7 ± 1.1 years [ mean ± SD ] ) , talented rugby league players completed the same periodized resistance-training program in either a supervised ( SUP ) ( N = 21 ) or an unsupervised ( UNSUP ) ( N = 21 ) environment . Measures of 3 repetition maximum ( 3RM ) bench press , 3RM squat , maximal chin-ups , vertical jump , 10– and 20-m sprints , and body mass were completed pretest ( week 0 ) , midtest ( week 6 ) , and posttest ( week 12 ) training program . Results show that 12 weeks of periodized resistance training result ed in an increased body mass , 3RM bench press , 3RM squat , maximum number of chin-ups , vertical jump height , and 10– and 20-m sprint performance in both groups ( p < 0.05 ) . The SUP group completed significantly more training sessions , which were significantly correlated to strength increases for 3RM bench press and squat ( p < 0.05 ) . Furthermore , the SUP group significantly increased 3RM squat strength ( at 6 and 12 weeks ) and 3RM bench press strength ( 12 weeks ) when compared to the UNSUP group ( p < 0.05 ) . Finally , the percent increase in the 3RM bench press , 3RM squat , and chin-upmax was also significantly greater in the SUP group than in the UNSUP group ( p < 0.05 ) . These findings show that the direct supervision of resistance training in young athletes results in greater training adherence and increased strength gains than does unsupervised training For many sporting activities , initial speed rather than maximal speed would be considered of greater importance to successful performance . The purpose of this study was to identify the relationship between strength and power and measures of first-step quickness  ( 5-m time ) , acceleration  ( 10-m time ) , and  maximal speed  ( 30-m time ) . The maximal strength ( 3 repetition maximum [ 3RM ] ) , power ( 30-kg jump squat , countermovement , and drop jumps ) , isokinetic strength measures ( hamstring and quadriceps peak torques and ratios at 608·s-1 and 3008·s-1 ) and 5-m , 10-m , and 30-m sprint times of 26 part-time and full-time professional rugby league players ( age 23.2 ± 3.3 years ) were measured . To examine the importance of the strength and power measures on sprint performance , a correlational approach and a comparison between means of the fastest and slowest players was used . The correlations between the 3RM , drop jump , isokinetic strength measures , and the 3 measures of sport speed were nonsignificant . Correlations between the jump squat ( height and relative power output ) and countermovement jump height and the 3 speed measures were significant ( r = −0.43 to −0.66 , p < 0.05 ) . The squat and countermovement jump heights as well as squat jump relative power output were the only variables found to be significantly greater in the fast players . It was suggested that improving the power to weight ratio as well as plyometric training involving countermovement and loaded jump-squat training may be more effective for enhancing sport speed in elite players Six men and six women trained the elbow flexors of both arms 3 d.wk-1 for 20 wk . In each training session , one arm did 3 - 5 sets of 10 maximal concentric actions on an accommodating resistance device ( ARD ) , the other arm 3 - 5 sets of 8 - 12 coupled eccentric/concentric actions ( repetitions ) to volitional failure ( 8 - 12 RM ) on a weight resistance device ( WRD ) . The average " intensity " ( force of concentric actions ) was approximately 1.25 times greater in ARD training , the average " volume " ( number of actions x force of actions ) 1.6 times greater in WRD training , and the time required to complete a training session the same for each . Both types of training produced significant increases in a single maximum weight lift ( 1 RM on the WRD ) , in the peak force of a single maximal concentric action measured on the ARD and an isovelocity dynamometer , and in biceps , brachialis , and total elbow flexor cross-sectional area ( CSA ) . Biceps Type I and II fiber area did not change significantly . WRD training produced greater increases than ARD training in the 1 RM test on the WRD and in brachialis CSA . The data indicate that both of these common training regimens effectively increase strength and muscle mass , but the weight training regimen may be more effective for increasing muscle mass The purpose of this study was to determine if three training loads equated by volume differed in terms of the temporal , kinematic and kinetic characteristics of each set . Twelve experienced weightlifters ( 30.2+/-10.6 years old and 75.8+/-13.0 kg ) performed three sets ( 6 x 30 % 1RM , 3 x 60 % 1RM and 2 x 90 % 1RM ) of ballistic squats on an instrumented supine squat machine . Repeated measures ANOVA and Tukey HSD post hoc comparisons were used to distinguish significant differences between the three training loads on a variety of temporal , kinematic and kinetic variables . Significantly ( p < 0.05 ) greater total time under tension during the eccentric ( 41 - 53 % ) and concentric phases ( 27 - 31 % ) was observed for the 30 % 1RM condition compared to the other two conditions . Similarly , the lighter loading intensity result ed in significantly greater total eccentric ( 9 - 19 % ) and concentric ( 14 - 24 % ) force output compared to the other two conditions . Greater total power output was associated with the 30 % 1RM condition for both the eccentric ( 25 - 48 % ) and concentric ( 40 - 69 % ) phases . Greater total work ( 9 - 24 % ) was also associated with the 30 % 1RM condition . The 60 % 1RM condition produced significantly greater total work , force and power compared to the 90 % 1RM condition . However , greater concentric impulse ( 29 - 42 % ) was associated with the 90 % 1RM condition . It is suggested that strength and power research needs to adopt a set kinematic and kinetic analysis approach within the research design s so that a better underst and ing of the nature of the neuromuscular adaptations elicited by different loading parameters is achieved The purpose of this investigation was to examine the effect of an 8-week training program with heavy- vs. light-load jump squats on various physical performance measures and electromyography ( EMG ) .  Twenty-six athletic men with varying levels of resistance training experience performed sessions of jump squats with either 30 % ( JS30 , n = 9 ) or 80 % ( JS80 , n = 10 ) of their one repetition maximum in the squat ( 1RM ) or served as a control ( C , n = 7 ) . An agility test , 20-m sprint , and jump squats with 30 % ( 30J ) , 55 % ( 55J ) , and 80 % ( 80J ) of their 1RM were performed before and after training . Peak force , peak velocity ( PV ) , peak power ( PP ) , jump height , and average EMG ( concentric phase ) were calculated for the jumps . There were significant increases in PP and PV in the 30J , 55J , and 80J for the JS30 group ( p < 0.05 ) . The JS30 group also significantly increased in the 1RM with a trend towards improved 20-m sprint times . In contrast , the JS80 group significantly increased both PF and PP in the 55J and 80J and significantly increased in the 1RM but ran significantly slower in the 20-m sprint . In the 30J the JS30 group 's percentage increase in EMG activity was significantly different from the C group . In the 80J the JS80 group 's percentage increase in EMG activity was significantly different from the C group . This investigation indicates that training with light-load jump squats results in increased movement velocity capabilities and that velocity-specific changes in muscle activity may play a key role in this adaptation Abstract Seventeen subjects performed resistance training of the leg extensor and flexor  muscle groups two ( 2/wk ) or three ( 3/wk ) times per week . Changes in the relative myosin heavy chain ( MHC ) isoform contents ( I , IIa and IIx ) of the vastus lateralis and isometric , isokinetic and squat-lift one-repetition maximum ( 1RM ) strength were compared between conditions after both a common training period ( 6 weeks ) and number of training sessions ( 18 ) . After 6 weeks and 18 sessions ( 9 weeks for the 2/wk group ) , increments in 1RM strength for the 3/wk and 2/wk groups were similar [ effect size ( ES ) differences ≈0.3 , 3/wk > 2/wk ] , whereas the 2/wk group presented greater isokinetic ( ES differences = 0.3–1.2 ) and isometric ( ES differences ≈0.7 ) strength increases than the 3/wk condition . A significant ( P < 0.05 ) increase in MHC IIa percentage was evident for the 2/wk group after 18 sessions . Both training groups exhibited a trend towards a reduction in the relative MHC IIx and an increase in MHC IIa contents ( ES range = 0.5–1.24 ) . However , correlations between changes in the strength and MHC profiles were weak ( r2 : 0.0–0.5 ) . Thus , isometric and isokinetic strength responses to variations in training frequency differed from 1RM strength responses , and changes in strength were not strongly related to alterations in relative MHC content This study was performed to determine which of three theoretically optimal resistance training modalities result ed in the greatest enhancement in the performance of a series of dynamic athletic activities . The three training modalities included 1 ) traditional weight training , 2 ) plyometric training , and 3 ) explosive weight training at the load that maximized mechanical power output .  Sixty-four previously trained subjects were r and omly allocated to four groups that included the above three training modalities and a control group . The experimental groups trained for 10 wk performing either heavy squat lifts , depth jumps , or weighted squat jumps . All subjects were tested prior to training , after 5 wk of training and at the completion of the training period . The test items included 1 ) 30-m sprint , 2 ) vertical jumps performed with and without a countermovement , 3 ) maximal cycle test , 4 ) isokinetic leg extension test , and 5 ) a maximal isometric test . The experimental group which trained with the load that maximized mechanical power achieved the best overall results in enhancing dynamic athletic performance recording statistically significant ( P < 0.05 ) improvements on most test items and producing statistically superior results to the two other training modalities on the jumping and isokinetic tests The purpose of this study was to explore the effects of 5 weeks of eccentrically loaded and unloaded jump squat training in experienced resistance-trained athletes during the strength/ power phase of a 15-week periodized off-season resistance training program . Forty-seven male college football players were r and omly assigned to 1 of 3 groups . One group performed the jump squat exercise using both concentric and eccentric phases of contraction ( CE ; n = 15 ) . A second group performed the jump squat exercise using the concentric phase only ( n = 16 ) , and a third group did not perform the jump squat exercise and served as control ( CT ; n = 16 ) . No significant differences between the groups were seen in power , vertical jump height , 40-yd sprint speed and agility performance . In addition , no differences between the groups were seen in integrated electromyography activity during the jump squat exercise . Significant differences between the CE and CT groups were seen in D 1RM squat ( 65.8 and 27.5 kg , respectively ) and D 1RM power clean ( 25.9 and 3.8 kg , respectively ) . No other between-group differences were observed . Results of this study provide evidence of the benefits 
    Output:
    
Conclusion Based on current findings , training frequencies of two to four resistance training sessions per muscle group/week can be prescribed to develop upper and lower body strength and power .
Strength levels can be maintained for up to 3 weeks of detraining , but decay rates will increase thereafter ( i.e. 5–16 weeks ) .
The effect of explosive-ballistic training and detraining on pure power development and decay in elite rugby and American football players remain inconclusive .
The long-term effects of periodized resistance training programmes  on strength and power seem to follow the law of diminishing returns , as training exposure increases beyond 12–24 months , adaptation rates are reduced