Adaptations to Resistance Training (from nasm)

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Adaptations to Resistance Training Article selection purposely was rigorous in an attempt to minimize confounding factors that can be evident from less well-controlled studies. We found 21 papers that satisfied the severe restrictions of this review. The studies could be categorized according to responses to training for strength, hypertrophy, and local muscle endurance. Studies are presented chronologically within each section. Many of the studies presented data in graphic form meaning effect sizes could not be determined. Rhea (2004) has proposed modifications for interpreting effect sizes in strength training studies ( Table 1 ). When effect sizes are presented, refer to this table to help in interpreting the magnitude of the effect. Operational definitions of training protocols are presented in Table 2 . Methodology in resistance training studies manipulates a wide variety of training variables.

Strength

For many fitness professionals, potentially large markets are the middle aged and older adults wishing to lengthen their active years with systematic training. Hakkinen et al (2000) investigated the train-ability of older adults. While there is ample early data that shows older adults are responsive to training, the nature of the response to resistance training is an important concept when designing training programs and following the progress of people in training. This project recruited 42 men and women who were blocked according to age and gender. Thus, four groups were established: men with an average age of 42 (M40, n=10)), men with an average age of 71 (M70, n=11), women with an average age of 39 (W40, n=10), and women with an average age of 67 (W70, n=10). These subjects were considered healthy and active with no resistance training background.
The training program was six months in length. Each subject was tested for isometric knee extension torque and 1-RM knee extension, each with EMG of the vastus medialis, lateralis, and biceps femoris. Testing was performed pre training and every two months of the study. Muscle biopsies of the vastus laterals were taken before and after training. The training program was a basic linear periodized program. For the first 2 months, the intensity progressed from 50-70% of 1RM. The intensity then progressed from 70-80% of 1RM over the next 2 months. The final two months were 3-6 repetitions of 70-80% of 1RM with 4-6 sets of 50-60% 1-RM. Training incorporated both heavy and explosive resistance training. All sessions were supervised.
Body mass and composition was unchanged throughout the study. Isometric peak torque was, as expected, greatest for the younger subjects. Each group improved torque output over the course of the study to similar degrees: M40=+28%, W40=+27%, M70=+27%, W70=+26%. Leg extension 1-RM also was improved: M40=+27%, W40=+35%, M70=+21%, W70=+31%. EMG assessment of (isometric and concentric ) extensor muscle activation was significantly greater for the vastus muscles for all age groups and unchanged in the biceps femoris for all 4 groups. Force-time curves (a statement on the rate of force production) again was increased in all four groups: M40=+21%, W40=+32%, M70=+21%, W70=+22%. Muscle fiber distribution was unchanged during the study. As expected, the males had larger mean fiber area of both major fiber types than women. Training, however, increased type I fiber area in the W70 group and type II overall, specifically the type IIb fibers, in both groups of women with no training-induced changes in fiber area in the men. The best correlation with torque output was with the percentage of type II fibers.
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These data demonstrate the impressive gains possible in novice, middle aged, and older lifters. Both isometric and dynamic force production as well as rate of force production. This combination of heavy resistance and explosive training was particularly effective at increasing the size of the type II fibers in women. If much of the age-associated decline in force production is related to a loss of muscle mass, a training program like this demonstrates the body's ability to adapt by increasing type II fiber area (in women) and the ability of the nervous system to activate muscles (in all ages and genders). Thus, a 2 day per week training program consisting of heavy resistance and explosive lifting techniques is an effective prescription for maintaining muscle mass or increasing factors of muscle mass. These types of adaptations often are cited as reasons why trained older individuals have fewer falls and are more stable in various activities of daily living in their age group. Both the neural and muscle adaptations, especially in the type II fibers, are important contributors Kraemer and colleagues conducted a very practical application of strength training for sports performance (AJSM, 2000). While there are a number of projects conducted using athletes, one factor that does not get studied routinely is the effect of the training program on specific aspects of the performance of skill in that sport. In this project, 24 female collegiate tennis players were matched on ability and randomly assigned to a control group (n=8), a low volume (n=8), or a high volume (n=8) resistance training program. The control group followed their normal program of tennis training while the low volume group did one set of a circuit of resistance training machines, 8-10RM of each exercise. The high volume group followed a periodized program (4-6RM, 8-10RM, or 12-15RM depending on the training day). Resistance training was conducted 2-3 days per week for 9 months.
Each subject was tested at 0, 4, 6, and 9 months of training. Body composition (skin-folds), anaerobic power output (counter movement jump, Wingate test), and 1RM for the machine leg press, free weight shoulder press, and bench press were all determined. The maximal serve velocity was also determined as a measure of tennis skill performance.
As expected, there were no differences in overall body mass between the three groups nor was there any change in body mass over the course of the study within each group. The periodized group did, however, show significant increases in lean body mass and decreases in fat mass over the nine months while the other two groups showed no changes over time. Peak power on the Wingate test and vertical jump height continually increased in the periodized group over the course of the study. The other two groups showed no such improvements. Dynamic muscular strength also followed a similar pattern over the course of the study. All three tests of strength were increased in the periodized group throughout the nine months of the project. The low volume group showed increases in all three lifts from pre-training to the four-month test date and these results were maintained for the remainder of the study at a level below that of the periodized group. There were no changes over time in the control group. Finally, tennis serve velocity increased in the periodized group at four and nine months with no changes in serve velocity seen in the low volume or control groups. Unfortunately, the data were presented as bar graphs, so it was impossible to determine effect sizes for this study.
There were two important findings from this study. First, strength training led to improvements in specific skill performance. This is important in that many think that supplemental strength training is for injury prevention and improvement in overall physical fitness, but probably would have little effect on actual skill performance. The data from this project clearly demonstrate that a periodized program could improve serve velocity, but that a lower volume training program had no effect on skill performance. This leads to the second important finding. There appears to be a threshold of training volume for resistance training to affect performance and continued development of strength. Simply performing resistance training is not enough to see any supplemental or skill-specific performance. To achieve the improvements in body composition, physical performance, and skill performance, the program needs to be of sufficient volume. While this project demonstrates this concept, the actual threshold remains elusive.
For some, training is a solitary endeavor. A training program is considered and carried out alone. Maybe the athlete trains with friends, but the details and practice of training are unique to each participant. While safety issues suggest that resistance training, especially free weight training, be performed with a partner, the primary purpose of the partner is safety. The fitness industry has seen a rapid expansion of professionals with special interest and expertise in resistance training. When their responsibility is to ensure that each client realize their personal fitness goals, these professionals often will directly supervise each training session, offering guidance and support. Mazzetti et al (2000) explored the effect of direct supervision by randomly assigning moderately experienced male lifters to follow a prescribed resistance training program to either a group who was directly supervised (n=10) or a group who were unsupervised when training (n=8). All had 1-2 years of experience and were equally matched on demographics and pre-study performance, although the supervised group had greater bench press 1-RM upon entering the study.
Strength performance was determined with 1-RM for the squat, bench press, jump squat power output, and endurance of the bench press (number of reps at 80% of 1-RM). Body mass and composition were also measured. Data was collected at outset and after 12 weeks of training. The subjects followed a periodized plan. The program began with a general preparatory phase (weeks 1-2, 3 sets, 12-RM, 3 days/week, 1-2min recovery between sets), a hypertrophy phase (weeks 3-6, 3 sets, 8-10 RM, 4 d/wk, 45-90s recovery), a strength phase (weeks 7-10, 3-4 sets, 6-8 RM, 3 d/wk, 1-2 min recovery) and a peaking phase (weeks 11-12, 2-3 sets, 3-6 RM, 3 d/wk, 1-2.5 min recovery).
Training logs were kept to determine training loads. The supervised group had a greater training load for the squat (beginning at the 7 th week) and for the bench (beginning with the 3 rd week). Both groups improved their squat and bench press performance. For the squat, the relative improvement was 33% and 25% for the supervised and unsupervised groups, respectively. For the bench press, the relative improvement was 22% and 15% for the supervised and unsupervised groups, respectively. Jump squat power output and bench press endurance both improved, but there were no group differences. The data were presented in bar graphs so an effect size could not be determined. Body mass and fat free mass increased in only the supervised group (fat free mass: supervised ES= 0.54, unsupervised ES= 0.16).
The impact of a personal trainer is obvious. The subjects advanced their training load at a faster rate and subsequent performance benefited. As local endurance responds to duration of training vs. intensity, and both groups followed a similar program, the lack of a group difference is not surprising. While not directly studied, it appears that the presence of the personal trainer fostered competitiveness and enhanced motivation, especially after the opening weeks of familiarization to the program. The trainer appeared to be beneficial in advancing the program by encouraging the subjects to tolerate greater training loads and the subsequent improvement in strength performance. This project offers objective evidence that optimal strength performance adaptations to a periodized program will be best when the athlete received personal supervision in research or in practice.
Many prescriptions for exercise stress the importance of resistance training to maintain muscle mass through the lifespan. While there are reports that show maintenance of muscle mass while aging, there is little data about the response of muscle in older individuals subjected to a high intensity training program. Izquierdo et al (2001) recruited middle age (average age=46y, n=11) and older (average 64y, n=11) men from a private recreational and physical fitness club to participate in a 16-week high intensity resistance training program. After passing a full medical clearance, the subjects underwent a series of strength, power, muscle mass, and hormonal assessments. A 1-RM was determined for a half squat and bench press. Testing at varying percentages of 1-RM for each lift produced a power-load curve. Muscle cross sectional area of the quadriceps was determined by ultrasonography; a reliable method with a low coefficient of variation. Cortisone, total and free testosterone were determined pre, mid and post study. The lifts used in training included leg extensions, arm extension and other multi-joint upper body, and core exercises all performed on machines. The training program was basically in 8-week segments. The first 8-weeks of training were 50-70% of 1RM (10-15 repetitions per set) for 3-4 sets of each exercise. During the next 8 weeks, the loads were progressively increased every four weeks. The training was considered to be a combination of heavy-resistance and "explosive" training. Routine daily and recreational activities were continued throughout the study.
Muscle cross sectional area, strength and power all improved in both groups. Quadriceps cross sectional area increased by a little over 10% in both groups (middle age: ES=0.8; older: ES=0.4). Overall mass and lean mass were unchanged, but there was a small decrease in body fat percentage (middle ES=2.0; older ES=0.4). There was a similar relative improvement in half squat 1-RM (middle age: 113 to 163kg, +45%, ES=1.9; older: 100 to 136kg, +41%, ES=1.5). Knee extension 1-RM also improved by similar percentages (middle age: 75 to 95kg, +29%, ES=2.0; older: 59 to 73kg, +25%, ES=1.3). The degree of improvement was greatest over the last 8 weeks of the study. Knee extension isometric force improvements were similar. Bench press 1-RM followed a similar pattern (middle age: 58 to 80kg, +36%, ES=1.4; older: 47 to 64kg, +36%, ES=1.7). The power-load curves for leg extension and bench press were all improved. The only blood parameter to change over the course of the study was a reduction in cortisol at week 16 in the older subjects.
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Despite the small subject number and resultant questions about statistical power, the authors were confident in saying that middle aged and older men following this high resistance program, performed only twice per week, were able to demonstrate significant force and power improvements. While the relative improvements were similar for the two age groups, as expected, the absolute loads were greatest for the younger subjects. The greatest degree of improvement occurred in the second 8-week period, especially in the middle aged group, when the intensity of training was periodically increased. The older subjects failed to improve to the same degree when the loads were increased suggesting the program they were following might have been near their physiological limits. These improvements in strength performance of the legs were associated with a significant improvement in quadriceps cross-sectional area. The subjects in this study all had serum values within the normal ranges. In past studies, subjects whose serum results improved were hypogonadal when they began training. Based on these results, a high intensity resistance program would allow men of this age to maintain their activities of daily living that require strength and power output instead of continuing to lose muscle mass and function.
Clinicians have been applying exercise as a treatment mode in various disease states for symptomatic or clinical benefits. For example, fibromyalgia's symptoms predominantly are localized to soft tissue, particularly skeletal muscle. In some patients, muscular strength is hindered while in others, there is no effect on strength reported. Hakkinen et al (2002) conducted a training study on women with fibromyalgia to see if resistance training would be beneficial for this clinical population. They also looked at hormonal modulators of muscle mass and strength to look for potential interactions of training, hormones, and fibromyalgia.
They randomized 21 pre-menopausal women with clinically diagnosed fibromyalgia into a training (n=11) or a control (n=10) group. Twelve healthy controls were also recruited. After a 4 week control period, 21 weeks of training followed. Strength was measured as the isometric force of the knee extensors and flexors. EMG was collected at the same time as the force measurements. Cross sectional area of the thigh muscles was obtained using MRI. The hormonal panel included testosterone, growth hormone, IGF-1, and DHEA sulfate. Patient reported muscle pain was obtained 1 week prior to each test period. The 2 day per week training program was directed at the thigh muscles, but other exercises for the trunk and upper extremity were performed. Intensity increased (and repetitions decreased) in 7 week blocks. Acute hormone responses to heavy labor were determined after a heavy session of 5 sets of 10RM.
Maximum knee extension and flexion force increased 18% and 13% respectively in the patients in the training group and 22% and 26% in the control group. There were no changes in the untrained patient group. EMG showed increased neural activation in the training groups. Both training groups increased the cross sectional area of the quadriceps, 7% for the patient group and 9% for the controls. There were no changes in the hormonal panel at basal testing, but growth hormone did show a post exercise increase in the training groups.
It was interesting that patients with a disease that affects skeletal muscle increased their thigh muscle strength, neural activation, and cross sectional area. Their responses to training were similar to age matched controls. The hormonal panel was consistent with controls. Thus, there appeared to be a value to using resistance training in women with fibromyalgia in helping them manage their disease.
The dizzying array of training variables and potential interaction of these variables suggests that a person attempting to train without the guidance of a trained fitness professional may well design a program that will not be appropriate for their fitness goals. After decisions are made about sets, reps, and loads, the program needs to be planned according to progression, which means there must be considerations about the various ways to periodize the program. Throughout this review are papers that compare a periodized vs. some more traditional program with results favorable for a periodized program. But there are a number of types of periodization and few papers that directly compare these methods. Rhea et al (2002) compared a linear vs. a daily undulating program. The challenge of these types of comparative studies is how to control for other training variables. In this study, training volume and intensity were held constant. Traditional periodization varies volume and intensity during macro, meso, and micro cycles over numerous weeks. The undulating cycle varies these factors daily or weekly. This study was a head-to-head comparison of linear vs. daily undulating periodization cycles.
Twenty college age males were recruited from weight training classes. Each had been in a strength training program for the prior two years following essentially a linear program. Body composition was determined using the Bod Pod. The program was 12 weeks in length and testing for 1-RM bench and leg press was conducted at 0, 6, and 12 weeks. The subjects were randomly assigned to a group with 10 men in each group. The program was 3 days per week and took about 40 minutes to complete. The program focused on the bench and leg presses, but also included crunches, biceps curls, and lat pull downs. No other strength training was permitted. The linear group did 3 sets of 8-RM for weeks 1-4, 3 sets of 6-RM for weeks 5-8, and 3 sets of 4-RM of each lift. The daily undulating group did 3 sets of 8-RM on Monday, 3 sets of 6-RM on Wednesday, and 3 sets of 4-RM on Friday. One week of active rest occurred between weeks 5 and 6.
There were significant increases across time on absolute force output for the leg press for each group, but no changes in bench press performance. Relative increases were greatest for 0 to 6 weeks and from 0 to 12 weeks for both groups for each lift. Bench and leg press performance increased by 14% and 25% respectively for the linear group. Bench and leg press performance increased by 29% and 56% respectively for the undulating group. These increases for the undulating group were significantly greater than the increases for the linear group. There were no changes in body composition.
The undulating program provided the necessary stress and variation to yield greater responses than did the linear program. The subjects in this study had resistance training experience and whether similar results would be seen with novice, elite, or elderly subjects would only be speculative. The small sample size and narrow subject selection of this study make generalizations difficult. Another concern is the potential for overreaching and overtraining. Some subjects in the undulating group complained of fatigue and muscle soreness late in the study suggesting that close monitoring of people training using this undulating method may be warranted. If the program is planned to achieve a peak performance at the end of this cycle, fatigue and soreness could well diminish power output and performance. However, these data support the use of an undulating periodized program over a traditional linear program to improve strength performance and avoid a plateau reported in long term use of linear programs. An added benefit to following this type of program is the increase in strength in the absence of changes in body mass that might be beneficial for athletes in weight restrictive sports like wrestling, boxing, competitive weight lifting, or the so-called aesthetic sports of gymnastics, diving, or dance. The authors cautioned against the uncontrolled use of an undulating program because of the risk of overtraining. So far, the optimal during of an undulating cycle has not been established so close monitoring is needed. With symptoms being reported late in a 12 week cycle, extending a cycle beyond this duration might not be advised.
The debate surrounding one vs. multiple sets is based on conflicting work where some show that multiple sets are superior and others show that the gains from a single set are the same--meaning a program can be carried out in less time. In their review of the published literature, Rhea et al (2002) point out 3 specific limitations. First, in many cases, pretest measures were not conducted which limits the ability to discuss the relative improvements in performance. Second, the rest interval between sets was not controlled being unstated in some studies and up to 30 minutes in other studies. Finally, the training intensity was uncontrolled. With some many potential factors potentially offering alternative explanations about the results, a conclusion about single vs. multiple sets remains elusive.
This project was a designed test: 1 vs. 3 set training over a 12 week program. Eighteen men from a college weight training class were recruited and randomly assigned to either 1 or 3 sets of training. All subjects had at least 2 years of recreational lifting experience; however, two subjects were taking creatine and were excluded. A 1-RM was determined for both the bench and leg press and body composition was determined using a Bod Pod. Testing was conducted pre training, at 6 and 12 weeks of training. Each group trained 3 days per week using a daily undulating cycle where the intensity was 8-10RM, 6-8RM, and 4-6RM for the first, second, and third training day of the week. One week of active rest was scheduled between weeks 5 and 6. The 3 set group was allowed 1-2 minutes rest between sets. The 1 set group also performed exercises unrelated to the bench and leg press to equate the total training time for the 2 groups.
The overall increase in 1-RM for the leg press was 26% and 56% in the 1 and 3 set groups, respectively. For the bench press, the overall improvements were 20% and 33%, respectively. For the 1 set group, the bulk of the improvements occurred in the first 6 weeks. The effect sizes for the 3 set group (1 set group as the controls) were 2.3 for the bench press and 6.5 for the leg press. Such large effect sizes for the 3 set group confirm just how much better 3 sets are than 1 for improving bench and leg press strength. While 1 set is effective at improving strength, multiple sets caused even greater gains in strength. Selection of the number of sets needs to be considered based on the goals of the training program. The goals of some may not be for maximal strength gains and could use a single set program while those whose desire is maximal strength gains would be advised to use multiple sets.
Circuit weight training is a time-efficient method that has become quite popular with people looking to vary their workout routine. One selling point is based on reports that circuit weight training also improves cardiovascular fitness. Because of this bonus, circuit weight training has become a staple of cardiac rehabilitation programs to improve strength, local muscle endurance, and whole body endurance in a time efficient setting. While there are numerous studies on the adaptations to more traditional resistance training regimens, Harbor and colleagues (2003) wanted to verify the nature of the training response to a circuit weight training program, a topic that had not been seriously pursued in the literature.
This was a small study with of only 12 sedentary men performing circuit weight training for 10 weeks. Subjects were randomly assigned, according to a 2:1 procedure to either a training (n=8) or a control (n=4) group. Body composition (by underwater weighing), a series of 1-RM values for all 10 exercises used in training, muscle biopsies, and hormonal values (lactate, testosterone, cortisol) were determined before and after the training program. The training program was periodized over the 3 days a week, 10-week program. The duration of each set was to be 20-30 seconds in length with a 10-30 second rest period between each set. All major muscle groups (no core or trunk stabilizers) were activated during the training program that was conducted on Nautilus and Hammer Strength devices.
This program led to no statistical changes in body composition with the effect size of any changes being small according to the authors (0.22 to 0.38). Nine of the 10 exercises were significantly improved by circuit weight training with effect sizes ranging from 0.6 (chest press) to 2.24 (leg press). No significant improvement was seen for the leg curl exercise. While changes in fiber type percentages were not expected nor found, the cross sectional area of the type IIa fibers and the myosin heavy chain expression for IIa fibers both increased. Testosterone and cortisol were unchanged by this protocol.
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This study did not have a group undergoing traditional resistance training so the results were compared with historical data in the literature. The improvement in strength, such as the 15% increase in leg press 1-RM and 37% increase in the chest press were stated to be consistent with the literature. The authors felt that these increases in the absence of an increase in fat free mass (+3%, ES=0.22) support the role of neural factors in strength performance. The adaptations to the type IIa fibers, the more oxidative of the type II fibers, emphasizes that this protocol had an effect on the subset of fibers. Equipment issues prevented determination of VO2max, but (unpublished) treadmill time to exhaustion was unchanged by the training.
This study had a number of limitations. For example, the small sample size reduces the statistical power of the project. While the absolute changes in body composition were consistent with significant changes in the literature, no body composition results achieved statistical significance in this project. The small numbers also impact effect sizes. Not doing a test of muscle endurance was probably an oversight. The study had no traditional training group forcing comparison with the literature. This study has generalizability issues. The subjects were sedentary with no training experience of any kind for at least 12 months prior to the project. While this group would be applicable for other sedentary groups, many studies use subjects with some measure of recent weight training experience. Thus, comparing the results to the literature requires finding other studies with sedentary subjects. Few studies in this review used purely sedentary subjects. Despite these limitations, circuit weight training was effective at improving muscle strength in untrained individuals.
In a follow-up to their earlier training study on female tennis players, Kraemer and coworkers (2003) varied the training protocol. The earlier study (Kraemer, 2000) compared a single set training protocol with a linear periodized program. In this project, a non-periodized program (constant resistance and volume) was compared with a non-linear periodization program.
A total of 30 female collegiate competitive tennis players were randomly assigned to one of three groups: control (n=8), periodized (n=9), and constant (n=10). As before, a wide range of performance measures were assessed at 4, 6, and 9 months of training: body composition; anaerobic power; aerobic capacity; sprint speed and agility; handgrip strength; 1-RM for the leg bench, and shoulder press; ball velocity for the serve, forehand, and backhand; and a panel of hormonal variables. All women in the resistance training groups trained 3 days per week. Those in the constant group performed 2 sets of all 11-12 exercises and 3 sets of 4-5 of the exercises (depending on the day), 8-10RM for the duration of the study. Those in the periodized group did the same except they performed 4-6 RM on Monday, 8-10 RM on Wednesday, and 12-15 RM on Friday. The control players performed routine tennis training.
While there were no significant differences in body composition at any time point between the three groups, both resistance training groups increased fat free mass and reduced body fat percentage during the study. Anaerobic power (Wingate test) was best in the periodized group at 4 and 6 months, but by 9 months, the two training groups were similar. VO2max decreased over time in the training groups. Sprinting speed (10 and 20m) and agility were unchanged with time or between groups. Both groups improved their vertical jump performance, but by 9 months the periodized group showed a greater relative improvement in jump height over the constant group (50% vs. 37% respectively). Grip strength for both hands increased with training without any group effect. The 1-RM for the leg press increased more rapidly in the periodized group, but by 9 months both groups were similarly increased (19% vs 17% for the periodized and constant groups respectively). The same pattern was evident for the bench press, but the relative improvements favored the periodized group over the constant group (23% vs. 17%, respectively). There were nearly identical improvements in shoulder press 1-RM, again with the periodized group gaining strength earlier in the program. Both groups improved ball velocities; however, the periodized group had greater relative increase in service (29% vs. 16%), forehand (22% vs 17%), and backhand (36% vs. 14%) ball velocities.
This project showed that a daily, periodized resistance training program was superior to a constant training program. The improvement in the three measures of ball velocity seemed to be a result of improved strength. While both methods improved strength, the addition of training variation resulted in greater improvements. In the long run, the relative improvements were similar; the periodized program produced more rapid initial gains, a factor to be considered when designing supplemental strength training programs. Based on these results, this type of training program was not specific enough to impact speed and agility. Anaerobic power increased rapidly in the early portions of the program, but failed to continue to improve demonstrating the difficulty in continuing to improve anaerobic power over a long competitive season. Thus, a season of competitive tennis training probably should focus on maintaining, rather than improving, anaerobic power. The lack of significant responses of the hormonal panel indicates that tennis training is not sufficiently demanding to require adaptations. The definitive differences in training programs affect both the rate and magnitude of improvement in various performance measures. These differences are important when planning supplementary training programs for competitive sports.
Another application of the linear vs. undulating periodized programs investigated whether similar results would be found for local muscle endurance. Another project by Rhea and colleagues (2003) compared linear and daily undulating programs while adding a third group that followed a reverse linear program where volume is gradually increased and intensity decreased over the course of the study. The purpose was to compare the effect of these three types of training programs on local muscle endurance. Many endurance runners are adding supplement resistance training to their training program for a number of reasons including improving local muscle endurance. Improving local muscle endurance increases running economy and endurance performance.
This comparatively large project studied 60 men and women who were recruited from university weight training classes, all of whom had at least 12 months, but no more than 5 years, of weight training experience upon enrollment. Over the course of the 15-week training program, the subjects had to only do the prescribed exercises for their lower extremities. After random assignment to groups (10 men and 10 women to each group), local muscle endurance was assessed as the number of leg extension repetitions at 50% of their own body weight. Testing was done at the beginning, the 7 th and 15 th week of training. A 1-RM for leg extension was also determined pre and post training. The training programs were equated for volume and intensity. The training program was held twice per week and focused on leg extension. The linear group (operationally defined as the control group) followed a periodized program where the performed 3 sets of 25 repetitions for weeks 1-5, 2 sets for 20 repetitions for weeks 6-10, and 3 sets of 15 RM for weeks 11-15. The reverse linear group did just the opposite. The undulating group followed the linear pattern over a 3-day cycle and repeated throughout.
As planned, there was no difference in the total volume of work performed over the 15 weeks. Local muscular endurance increased in all groups by 56%, 73%, and 54% in the linear, reverse, and undulating groups, respectively. There were no between group differences despite the relatively large improvement by the reverse group. The effect size for endurance of the reserve group (compared to the linear group) was 0.27 and for the undulating group was -0.02 (statistically significant, although trivial effect sizes). Strength as 1-RM improved by 9% (from 79 to 85kg), 6% (73 to 77kg), and 10% (74 to 81kg) for the linear, reverse, and undulating groups, respectively. Again, there were no between group differences, born out by the trivial effect sizes (ES reverse training=-0.31; undulating training=0.04; again statistically significant). Leg circumference was reduced by 1-1.5%.
All three programs were effective at improving local muscle endurance. The magnitude of the effect size for the reverse program, while significantly better than the undulating effect size, should still be considered trivial. When comparing results between the linear vs. the reverse training programs, the gradual increases in repetitions in the reverse program was more effective at improving endurance. Some might question the use of body mass for determining endurance resistance, placing larger subjects at a disadvantage. Results for men and women were pooled leading to rather large variances. Also, the wide range (1-5yrs) of prior lifting experience could also have contributed to the wide variations. The authors did not measure muscle or fiber area and could only speculate about why there was a small reduction in leg circumference. Because both the linear and undulating groups improved strength and the reverse had the greatest effect on endurance, recommendations on the type of program should be based on the goals of the training program. Based on these results, when endurance athletes are attempting to improve local muscle endurance to achieve the expected improvements in running economy and performance, a reverse protocol is probably the best option.


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