Local Muscle Endurance training (from nasm)

jacky

Local Muscle Endurance Local muscle endurance is generally assessed according to the number of lifts successfully performed at some submaximal resistance--typically a multi-joint lift (e.g., squat, bench press, leg press) against a resistance ranging from 60-80% of 1RM. Most studies focus on a variety of aspects of resistance training with local muscle endurance as one aspect of many. As frequently noted, the number of training variables for resistance training (e.g., sets, reps, intensity, rest period, types of lifts, progression, experience of the subjects) means that studies can be quite different while still addressing the same topic. A large number of studies were reviewed, but only a few met all the inclusion criteria of this review.
Hass (2000) concentrated on the effect of training volume on strength, endurance, and body composition in recreational lifters. With most studies showing the importance of intensity on lifting performance, the authors felt that while both groups would improve on the various performance factors, increasing the number of sets would not lead to even more improvements.
This study selected subjects from a commercial fitness center ranging in age from 20 to 50 years of age. All the subjects had a lifting history (6 years) typically training three days per week. A total of 42 subjects were randomized to either 1 or 3 sets for each exercise of a nine machine circuit. Each set was 8-12 repetitions, each lift was a 2 second concentric and a 4 second eccentric phase. The load was increased 5-10% once 12 repetitions were performed for any lift. The subjects in the 3 set group were allowed 3-5 minutes between circuits. The full training program was 13 weeks in length. The training program used the MedX system (MedX Corp., Ocala, FL)
Muscle strength was determined with a 1-RM for leg extension, leg curl, chest press, overhead press, and biceps curl. Tests were conducted pre-training, mid-study, and post-training. After a warm-up, each subject loaded the machine to the prestudy training load. Resistance was progressively loaded until the 1-RM was achieved. Two sessions, separated by 48 hours, were required to determine 1-RM for all the maneuvers. Bilateral, isometric testing of knee flexion and extension at 6 different angles of knee flexion was also determined. Local endurance was determined for the chest press and leg extension. After a warm-up, the subjects performed the lift as many times as possible at 75% of their pre-training 1-RM. Anthropometrics (skinfolds, diameters, and circumferences) were used to determine body composition.
A total of 49 initially enrolled, but 42 completed the study (30 females). Failure to adhere to the protocol or injury necessitated exclusion from the project. As expected, chest press and leg extension 1-RM increased significantly (results were reported in bar graphs, thus effect sizes could not be determined) for both groups. In most cases, the increase in strength was between 5 and 10% from pre-training to mid-study to the post training tests. There were no differences in between groups on any of the lifts. Isometric strength improved, but not at every angle. Again, there were no group differences.
Muscle endurance for both lifts increased for each lift. For the one-set group, endurance for the chest press and leg extension increased by 48% and 49%. For the three-set group, endurance increased by 58% and 67%, respectively. While both groups improved their local muscle endurance, there were no differences between groups for either lift.
Both groups increased their lean body mass, but again, there were not differences between the training groups. Of all the data collected and the various ways to represent the results, the only variable where the three-set group was significantly better than the one-set group was for leg curl strength as kg/kg lean mass (effect size = 1.0).
Kraemer conducted another multi-center trial; this time adding a military site (Kraemer, 2001). This broad study looked at performance responses to a wide variety of training protocols, some of which were not resistance based programs. They applied different periodized programs to a sample of military women for six months to see just how strength, power, endurance, and military occupational tasks were affected. In addition, the results were compared with active, but not resistance trained men to learn more about gender differences.
The women were assigned to one of six training protocols: total strength/power, total strength/hypertrophy, upper body strength/power, upper body strength/hypertrophy, field exercises, or aerobic training. The resistance programs were periodized as a 24-week macrocyle and two 12-week mesocycles separated with a 3-week period of active rest. The aerobic group training was also periodized on a similar schedule. Field training included plyometrics, calisthenics, and partner-resisted activities.
As before, subjects were tested pre training, mid study (3 months) and post training (6 months). Tests included anthropometrics, 1-RM for squat, bench press, high pull and box lift, power tests (squat jump, bench press throw), squat endurance, repetitive box lift, 2-mile loaded run, and the US Army physical fitness tests. All resistance data was collected using the Plyometric Power System. Eleven to 18 women were assigned to the training groups. A total of 100 men were tested for gender comparisons.
When viewing the pre- vs. post-training results, lean mass increased in only the total strength/power (ES=.42) and field training groups (ES=.27). This study had numerous outcomes, but for the purposes of this section, only the local muscle endurance results will be reported. These include the squat endurance and repetitive box lift, and the 2-mile loaded run.
At the 6-month test period, the total strength/hypertrophy group outperformed the field and aerobic training groups on the squat endurance (number of proper repetitions of 45.4kg). After training, there were no differences between the total strength/power or the total strength/hypertrophy when compared with the men. For the repetitive box lifts (move as many 20.45kg boxes from the floor to a platform 1.32m from the floor), all resistance groups outperformed the field and aerobic groups. After training, there were no gender differences between the resistance trained women and the men. The field and aerobic trained women performed best on the 2-mile loaded run. Effect sizes were not reported. Data was reported in bar graphs, so an accurate effect size could not be determined.
Overall, the 6-month resistance training programs were effective at improving local muscle endurance as well as reducing the differences between men and women, including performances on military tasks. The authors demonstrated the vital role of resistance training in enhancing physical performance.
In a multi-center project from Colorado to Indiana to Pennsylvania to Finland, Kraemer's group compared low volume vs. high volume resistance training in women (Marx, 2001). While the design of previous paper (Haas, 2000) was simple: 1 set vs. 3 sets, this paper added a periodization schedule to the high volume group.
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A total of 34 active, untrained women met the inclusion criteria and were randomly assigned to a single set circuit group, a high volume periodized group or a control group. The randomization procedure equated the subjects on age, height, mass, and body composition. Muscle strength for the bench and leg press was assessed as 1-RM on a Universal TM weight machines. Endurance of the same lifts was determined as the number of successful repetitions at 80% of their 1-RM. A one-minute sit-up test was also conducted. Other tests included the Wingate anaerobic power test, a standing vertical jump, and a 40-yard dash. Tests were conducted pre training, then after 3 and 6 months of training.
The single set training program subjects trained on 3 non-consecutive days, 8-12 repetitions (to momentary failure). Resistance was increased once the subject could perform 12 repetitions without assistance. Two separate circuits were devised to relieve boredom and staleness. Both circuits used 10 different exercises for the arms, shoulders, trunk, thighs, and legs.
The high volume group followed 2 circuits over their 4-day week. One circuit was performed on Monday and Thursday (7 exercises, 2-4 sets each) while the other was performed on Tuesday and Friday (12 exercises, 2-4 sets each). On Monday and Thursday, the intensity varied from high (3-5RM), moderate (8-10RM), or light (12-15RM). Resistance was moderate on Tuesday and Friday. Loads were increased once the subject could perform the desired number or repetitions without assistance. How much the loads were increased was not stated for either group.
The control group did no resistance training. With makeup days allowed on weekends, all training subjects completed 100% of the training session for the full 24 weeks.
Both groups maintained overall mass, but each lost fat with the low volume subjects decreasing from 15.5% to 23%, while the high volume subjects decreased from 16.5 to 19.8% (low volume ES=.69, high volume ES=1.4). This means both groups gained muscle mass (low volume ES=.2, high volume ES=.62) by the end of the study. Strength, as 1-RM, increased for both lifts in both groups. Bench press 1-RM for the low volume subjects increased from 22.1kg to 24.8kg while the high volume group increased from 21.8kg to 32kg. Leg press strength increased from 95.6 kg to 106.3 kg and from 95.5kg to 126kg for the low and high volume groups, respectively. The effect size of the increase in bench and leg press strength was 1.7 and 1.4, respectively for the low volume group. Yet, the effect sizes for the bench and leg press in the high volume group was markedly larger as 6.4 and 4.7, respectively.
The improvements in local muscle endurance followed a similar course; a good response in the low volume group, but a more substantial response in the high volume group. The effect size for bench press endurance in the low volume subjects was 1.25 (from 9.6 to 10.6 reps) and for the leg press the effect size was 1.6 (from 11.2 to 13.3 reps). Both results are excellent. But the high volume group showed some very impressive effect sizes. For the bench press, the effect size was 4.6 (from 9.5 to 11.8 reps) and for the leg press the effect size was 4.3 (from 11.3 to 18.6 reps), among the highest reported for resistance training studies. Similar relationships were seen for the Wingate peak power (low ES=.54, high ES=2.68), sit-ups (low ES=1.4, high ES=6.5), vertical jump (low ES=2.05, high ES=5.2), and 40-yard sprint (low ES=.16, high ES=2.1).
The data was pretty conclusive that a high volume resistance training program led to greater responses in previously untrained women that is similar to results in men. While the volume was substantially greater in the high volume group, there was also an intensity factor with the periodized approach. The authors were firm in their conclusion that "the variation of volume and intensity…is vital for improvement in muscular performance…" While this section's emphasis is local muscle endurance, such a program had far reaching effects on a variety of high power output activities.
Anyone with any experience with resistance training knows that different adaptations are possible depending on how the training variables are manipulated. Prior work has shown that the number of repetitions allowed by the level of resistance will dictate the nature of the adaptive response. Campos and colleagues (2002) compared low, intermediate, and high repetition resistance training to see where along this "repetition maximum continuum" specific adaptations occurred.
The study included 32 young men who were randomly assigned to one of four groups for this 8-week training study. The low repetition training group (n=9) trained at 3-5RM with 3 minutes rest between sets, the intermediate training group (n=11) trained at 9-11RM with 2 minutes of rest, the high repetition training group (n=7) trained at 20-28 RM with 1 minute rest between sets, and a control group (n=5). The frequency of training was 2 days per week for the first 4 weeks and 3 days per week for the last 4 weeks. Total training volume was equal. The point of focus was the vastus lateralis muscle. Body composition was estimated by skinfolds. Aerobic capacity was determined on a cycle ergometer. Strength (1-RM) was measured for the leg press, squat, and leg extension) and endurance was determined as the number of repetitions at 60% RM. Muscle biopsies were taken to measure muscle fiber composition, cross sectional area, capillary density, and selected biochemical assays. These tests were performed before and after training.
After training, only the high repetition group improved aerobic power output (watts) and time to exhaustion. There were no changes in whole body oxygen consumption. The total volume of work was similar between all three groups, as planned. All three groups improved their 1-RM measures. The low repetition group had the greatest gain in the leg press and squat exercises. Conversely, the high repetition group showed the greatest gain in local muscle endurance in all three exercises. The intermediate group also showed a significant increase, but not to the same magnitude as the high repetition group. Muscle fiber composition was unchanged throughout (although some trends were evident specific to the type of training performed), but the low repetition group showed significant increases in types I and IIb areas while the intermediate group increased all three major fiber populations. There were no significant changes in cross sectional area in any of the fiber types for the high repetition group. The capillary density for all three major fiber types increased in all 3 groups, but the only statistically significant increase was in the number of capillaries per type IIa fiber in the intermediate repetition group.
While there were some trends toward fiber composition alterations, the more distinctive changes were specific to the training impulse; the high repetition group improved in local endurance while the low repetition improved their 1-RM. In the short term, low and intermediate repetition training induced somewhat similar responses. Adaptations were specific to the intensity and the number of repetitions.
Another variable in designing strength training programs is the rest interval between exercises and sets. In many programs, as the resistance increases, so does the rest interval to allow for recovery of short-term energy sources (ATP and phosphocreatine) and eliminate fatigue inducing waste products (e.g., hydrogen ions). An appropriately applied rest interval will then restore force production. While longer rest intervals may well reduce the total number of repetitions and impact the total training volume, applying the shortest rest that allows for rectifying energy and fatigue issues should allow the athlete to sustain repetitions and keep intensity high for best gains in strength. Willardson and Burkett (2006) studied three different rest intervals on multiple sets of either heavy or light bench press loads.
This was not a training study. Sixteen recreationally trained lifters (mass=92kg, bench 1-RM=119.9kg) who practiced bodybuilding training volunteered to participate in the 4-week study. During week 1, a 1-RM for the bench press was determined. Over the next 3 weeks, each subject was tested twice per week (72hr between session). Tests on the first day used a load corresponding to 80% of 1-RM and the second day, the tests used a load of 50% of 1-RM. On each day, 5 sets were performed to voluntary exhaustion. A different rest interval (1, 2, or 3 minutes) was used each week (counterbalanced design).
For the five sets at the 50% load, the average number of reps at 1, 2, and 3 minutes were 59, 75, and 88 respectively. For the five sets at the 80% load, the average number of reps was 18, 23, and 27. The differences between each recovery interval were significant for each load. Focusing on the individual sets showed that the greatest decline in reps occurred from the first to the third set, after which the number of reps performed plateaued (e.g., 2 min rest, 80% 1-RM reps per set = 9.1, 5.2, 3.4, 2.8, 2.6; 1 min rest, 50% 1-RM = 29.9, 10, 7.1, 6.1, 6.1).
Regardless of the recovery time, the ability to perform the task was consistent in that there was a rapid decline in number of reps to failure over the first 3 sets before plateauing. When the rest interval increased, the level of the plateau also increased. The plateau began at about set 3, so for the 50% of 1-RM load, the number of reps to fatigue were 7.1, 11.2, and 14.1 for 1, 2, and 3 minutes of rest, respectively. This project might be considered as applicable to an undulating cycle of training, so that on a day when the goal is strength development, the rest interval should be 3 minutes to avoid the significant declines in repetitions. In addition, if the sets are restricted to a specified number and not done to failure, 1 or 2 minutes of rest should be realistic because of the reduced metabolic demand. If with 3 minutes of recovery, repetitions cannot be maintained, the authors suggested reducing the resistance. At the outset of a new program, the authors suggested a 3 minute recovery period that gradually is reduced to 1 minute as conditioning improves, based on the ability to sustain the number of repetitions with consecutive sets.


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