The effects of adding high-intensity of effort resistance training to routine care in persons with type II diabetes: An exploratory randomized parallel-group time-series study

AIMS

This study considered the effects of supervised, low volume, high intensity of effort resistance training compared to continued routine care in persons with type II diabetes.

METHODS

We utilized a randomized parallel-group time-series design. All participants completed baseline testing (T0) and then participated in an educational training intervention regarding the management of their diabetes and were followed up for six months, during which they received routine care before being retested (T1). Participants were then randomly allocated to either continue with routine care (CON) or receive the high intensity of effort resistance training intervention (HIT). Participants from both groups were retested again after six months (T2). All participants were followed up for a further 12 months before being finally tested (T3). Data were available from 57 participants who completed the whole duration of the study (HIT, n = 29; CON, n = 28) for measures of anthropometry (body mass, waist circumference, and BMI), body composition (body fat mass, body fat percentage, lean mass, and visceral fat mass), total body water, phase angle, HbA1c, fasted blood glucose, and subjective wellbeing (WHO-5).

RESULTS

During the initial 6-months of routine care significant improvements were noted for waist circumference, body fat mass, lean mass, body fat percentage, lean mass percentage, visceral fat mass, HbA1c, fasted blood glucose, and subjective wellbeing. During the successive 6-months (intervention) and 18-months (follow-up), data suggest that many of these positive changes during the initial 6-months were negated or reversed for CON. In contrast, participants engaging in HIT continued to show positive changes for waist circumference, body fat mass, lean mass, body fat percentage, lean mass percentage, and visceral fat. For blood markers and wellbeing, HbA1c continued to decrease, fasted blood glucose decreased, and subjective wellbeing continued to increase. These positive responses were still evidenced and significantly different compared to CON after the 12-month follow-up.

CONCLUSION

The results of this exploratory pragmatic trial suggest that the addition of high intensity of effort RT alongside routine care can have a positive impact on a range of outcomes in type 2 diabetics having undergone prior routine care.

Neither repetition duration nor number of muscle actions affect strength increases, body composition, muscle size, or fasted blood glucose in trained males and females

A key variable within resistance training (RT) is that of repetition duration: the time (seconds) taken to perform the concentric and eccentric muscle actions of a repetition. Research has produced equivocal results with regard to strength and muscle mass increases; many studies have created parity in the number of repetitions, but there has been disparity in the load used and the time under load (TUL). The purpose of this study was to compare load- and TUL-matched groups performing resistance exercise using different repetition durations. Fifty-nine male and female participants were randomized into 3 groups: 2s:4s (n = 18), 10s:10s (n = 20), or a group that performed 30 s of eccentric, 30 s of concentric, and 30 s of eccentric muscle actions (e.g., 1.5 repetitions; n = 21). Participants were supervised in one-on-one RT sessions 2 days/week for 10 weeks. Outcomes were 10 repetitions maximum (RM) and predicted 1RM for chest press, leg press, and pulldown exercises, as well as body composition, upper arm and thigh muscle mass, and fasted blood glucose. Analyses revealed significant increases in strength for all exercises but no between-group differences and no statistically significant time course changes for the other variables. Repetition duration does not affect the increases in strength in trained participants when exercise is performed to momentary failure. Because time constraints and perceived difficulty are often cited as barriers to exercise, it is important to recognize that the low-volume (single-set), machine-based protocol employed herein produced worthwhile strength increases in trained participants.

A minimal dose approach to resistance training for the older adult; the prophylactic for aging

A plethora of research has supported the numerous health benefits of resistance training as we age, including positive relationships between muscular strength, muscle mass and reduced all-cause mortality. As such, resistance training has been referred to as medicine. However, participation and adherence remains low, with time constraints and perceived difficulty often cited as barriers to resistance training. With this in mind, we aimed to summarise the benefits which might be obtained as a product of a minimal dose approach. In this sense, participation in resistance training might serve as a prophylactic to delay or prevent the onset of biological aging. A short review of studies reporting considerable health benefits resulting from low volume resistance training participation is presented, specifically considering the training time, frequency, intensity of effort, and exercises performed. Research supports the considerable physiological and psychological health benefits from resistance training and suggests that these can be obtained using a minimal dose approach (e.g. ≤60min, 2d-wk^-1), using uncomplicated equipment/methods (e.g. weight stack machines). Our hope is that discussion of these specific recommendations, and provision of an example minimal dose workout, will promote resistance training participation by persons who might otherwise have not engaged. We also encourage medical professionals to use this information to prescribe resistance exercise like a drug whilst having an awareness of the health benefits and uncomplicated methods.

Relations of Physical Self-Concept and Muscular Strength with Resistance Exercise-Induced Feeling State Scores in Older Women

Formerly sedentary older women ( M age = 62 yr.) were recruited for either a wait-list control group ( n = 40) or a 10-.wk., 3 days/wk. weight-training treatment group ( n = 48). Only the treatment group demonstrated significant before- to after-exercise improvements on the Exercise-induced Feeling Inventory scales of Positive Engagement, Revitalization, Tranquility, and Physical Exhaustion ( ds = |.43| to |.96|). For the treatment group, scores on Physical Self-concept of the Tennessee Self-concept Scale: 2 were significantly correlated (r = −.28) with after-exercise changes in Physical Exhaustion. Muscular strength was significantly correlated with after-exercise changes in scores on three Exercise-induced Feeling Inventory scales ( rs = |.28| to |.31|). Simultaneous entry of Physical Self-concept scores and muscular strength into multiple regression equations increased the explained variance in Exercise-induced Feeling Inventory score changes for each of its four scales. Statistical significance was only reached, however, on changes in the Physical Exhaustion scale ( R2 = .16, p = .02). Limitations and implications for theoretical development and applied use were discussed.

Comparison of Two Exercise Protocols on Fitness Score Improvement in Poorly Conditioned Air Force Personnel

A 12-wk. study was conducted to contrast the effects of a longer and more frequent aerobic exercise protocol with a shorter and less frequent circuit strength-training protocol for improving U.S. Air Force physical fitness test scores of subjects who previously failed to achieve a passing point total. 83 men and women of the U.S. Air Force ( M age = 32.7 yr.) participated in either the unsupervised standard conditioning program, which recommended approximately 60 min. of aerobic activity 4 to 5 days per week ( n = 26), or the supervised circuit strength-training program, which required approximately 25 min. of alternating strength and endurance exercises 3 days per week ( n = 57). Subjects were assessed on a 2400-m (1.5-mile) run, abdominal circumference, push-ups completed in 1 min., and abdominal crunches completed in 1 min. Dependent t tests with Bonferroni adjustment indicated that significant improvements were attained by the circuit strength-training group only on each of the aforementioned measures. Significantly more participants in the circuit strength-training group (26%) achieved a passing point total than in the standard conditioning group (19%) at Wk. 12 (χ12 = 3.96, p = .05). Implications for enhancing physical fitness in poorly conditioned adults were discussed.

Perceived Exertion during Resistance Exercise by Children

This pilot study examined the validity of a new scale of perceived exertion during acute bouts of resistance exercise in young children. The researchers developed an 11-point numerical scale with five pictures representing youths at various levels of exertion while lifting weights. 26 children ( M age 10.1 ± 1.2 yr.) performed one set of 10 repetitions at 35%, 55%, and 75% of their one-repetition maximum on the chest press and leg press exercises using child-size weight training machines. Scaling procedures for the perceptual anchors on the perceived exertion scale were based on one repetition maximum testing. Children could use this scale to translate into numbers their perceptions of physical exertion during upper and lower body resistance exercise. Perceived exertion distributed as a positive linear function of the percent of one repetition maximum on the chest press and leg press exercises ( rs = .70 to .77), and perceived exertion increased significantly across all three exercise intensities on both exercises. These preliminary findings provide partial evidence for validation when this scale was used during resistance exercise with children. Additional validation regarding perceived exertion during resistance exercise with children is warranted.

Nutrition programs enhance exercise effects on body composition and resting blood pressure

The purpose of our study was to examine the effects of exercise alone and exercise combined with specific nutrition programs on body composition and resting blood pressure rate. Adult participants (99 women, 22 men; aged 20-86 years) completed a combined strength and endurance exercise program (Exercise Only), or in conjunction with 1 of 2 nutrition plans (Exercise/Protein; Exercise/Protein/Diet). The Exercise-Only group performed 1 set of 9 resistance machines regimens interspersed with 3 bouts of recumbent cycling (5 minutes each). The Exercise/Protein group performed the same exercise program as Exercise-Only group, plus consumed 1.5 g of protein per kg of ideal body weight on a daily basis. The Exercise/Protein/Diet group followed an identical Exercise/Protein protocol along with a restricted daily caloric intake (1200-1500 cals/day for women; 1500-1800 cals/day for men). After 10 weeks of training, the Exercise/Protein group attained greater increases (P < 0.05) in lean weight and greater decreases (P < 0.05) in diastolic blood pressure (DBP) rate than the Exercise-Only group. The Exercise/Protein/Diet group experienced greater reductions (P < 0.05) in body weight, body mass index (BMI), percent fat, fat weight, waist circumference (WC), systolic blood pressure (SBP) rate, and DBP rate than the Exercise-Only group, as well as greater reductions (P < 0.05) in body weight, BMI, percent fat, fat weight, and WC than the Exercise/Protein group. Our findings suggest that a higher protein nutrition plan may enhance the effects of exercise for increasing subject lean weight and decreasing DBP rate. The findings further indicate that a higher protein and lower calorie nutrition plan may enhance the effects of exercise for decreasing subject body weight, BMI, percent fat, fat weight, WC, SBP rate, and DBP rate, while attaining similar gains in lean body mass.

Effects of the Youth Fit for Life Protocol on Physiological, Psychological, and Behavioral Factors at YMCA Calgary After-School Care Sites

Youth inactivity and inappropriately high weight is a problem in the United States, Canada, and much of the industrialized world. Physiological and behavioral changes associated with the Youth Fit For Life protocol, a physical activity and nutrition education treatment based on self-efficacy theory, were assessed in 7- to 12-yr.-olds ( N = 43) from Calgary, Alberta, Canada. Body Mass Index, strength, and cardiorespiratory endurance significantly improved over a 12-wk. period when contrasted with changes based on normative data. Significant within-group improvements in measures of self-efficacy, vegetable intake, and voluntary moderate-to-vigorous physical activity were also found over 12 wk. Multiple regression analysis indicated that score changes in measures of self-regulatory and task self-efficacy, and general self, accounted for changes in voluntary physical activity. Implications for use of behaviorally based methods for large-scale obesity prevention treatments in preadolescents were discussed.

Prescribing physical activity: applying the ACSM protocols for exercise type, intensity, and duration across 3 training frequencies

When physicians advise patients to attain more physical activity, they usually recommend a walking program. However, in a similar way to no exercise, those embarking on a walking program will typically lose 4 to 6 lb of lean weight and reduce their resting metabolic rate 2% to 3% every decade. These effects may be mitigated by the inclusion of resistance exercise. The American College of Sports Medicine (ACSM) minimum exercise guidelines recommend 20 minutes of aerobic activity 3 days per week, and 1 set (8-12 repetitions) of 8 to 10 resistance exercises to train the major muscle groups 2 days per week. However, large-scale testing of these recommendations in a field setting has been minimal. Men and women between 21 and 80 years (N = 1725) [corrected] participated in a 10-week combined strength and aerobic activity program based on the ACSM protocols for exercise intensity and duration across 3 training frequencies (1, 2, or 3 sessions/week). Across all training frequencies, mean changes included a reduction in body fat of 1.97%, a decrease in fat weight of 1.7 kg, an increase in lean weight of 1.35 kg, a reduction in systolic blood pressure of 3.83 mm Hg, and a reduction in diastolic blood pressure of 1.73 mm Hg. More frequent weekly training sessions were associated with greater improvements in body fat percent, fat weight, and lean weight. Participants responded favorably to the ACSM exercise program with a 91% completion rate and a 95% satisfaction rating. This article presents recommendations for prescribing safe, effective, and time-efficient exercise programs.

The H-Wave((R)) Device Induces NODependent Augmented Microcirculation and Angiogenesis, Providing Both Analgesia and Tissue Healing in Sports Injuries

The hypothesis that the H-Wave(R) device (Electronic Waveform Lab, Inc., Huntington Beach, CA), a small-diameter fiber stimulator, is a paradigm shift of electrotherapeutic treatment of pain associated with human neuropathies and sports injuries is based on a number of its properties. The primary effect of H-Wave(R) device stimulation (HWDS) is the stimulation of "red-slow-twitch" skeletal muscle fibers. The authors propose, based on the unique waveform, that the H-Wave(R) device specifically and directly stimulates the small smooth muscle fibers within the lymphatic vessels ultimately leading to fluid shifts and reduced edema. In unpublished rat studies, it has been observed that HWDS induces protein clearance. The H-Wave(R) device was designed to stimulate an ultra low frequency (1-2 Hz), low tension, nontetanizing, and nonfatiguing contraction, which closely mimics voluntary or natural muscle contractions. The H-Wave(R) device can stimulate small fibers due in part to its exponentially decaying waveform and constant current generator activity. The main advantage of these technologies over currently applied electrical stimulators (eg, transcutaneous electrical nerve stimulator [TENS], interferential [IF], neuromuscular electrical stimulation [NMES], high-volt galvanic, etc.) is that H-Wave\'s(R) small fiber contraction does not trigger an activation of the motor nerves of the large white muscle fibers or the sensory delta and C pain nerve fibers, thus eliminating the negative and painful effects of tetanizing fatigue, which reduces transcapillary fluid shifts. Another function of the H-Wave(R) device is an anesthetic effect on pain conditions, unlike a TENS unit which in the short term activates a hypersensory overload effect (gate theory) to stop pain signals from reaching the thalamic region of the brain. When the H-Wave(R) device is used at high frequency (60 Hz), it acts intrinsically on the nerve to deactivate the sodium pump within the nerve fiber, leading to a long-lasting anesthetic/analgesic effect due to an accumulative postsynaptic depression. Moreover, HWDS produces a nitric oxide (NO)-dependent enhancement of microcirculation and angiogenesis in rats. Thus, the authors hypothesize that because of these innate properties of the H-Wave(R) device, it may provide a paradigm shift for the treatment of both short- and long-term inflammatory conditions associated with pain due to sports injuries. A recent meta-analysis found a moderate-to-strong effect of the H-Wave(R) device in providing pain relief, reducing the requirement for pain medication, and increasing functionality. The most robust effect was observed for improved functionality, suggesting that the H-Wave(R) device may facilitate a quicker return to the field.

KEYWORDS

H-Wave(R) device; sportsmedicine, nitric oxide-dependent blood flow; analgesia; angiogenesis.

Relations of self-appraisal and mood changes with voluntary physical activity changes in african american preadolescents in an after-school care intervention

There is an increasing prevalence of overweight in preadolescents that predicts physical problems over the lifespan. Physical inactivity has been implicated as an associated factor, with African American youth being at an increased risk. Based on social cognitive theory, and proposed correlates of physical activity in youth, changes over 12 weeks in measures of self-appraisal (general self, physical appearance, physical self-concept, exercise barriers self-efficacy) and mood (tension, vigor), and their relations with voluntary physical activity changes, were assessed within an after-school care physical activity intervention. Participants were volunteers recruited from children already registered for a 12-week segment of YMCA after-school care. The treatment group consisted of 146 African American preadolescents with the control group comprised of 123 African American preadolescents who were scheduled to receive the program during the next sequence that it was offered. Results indicated the intervention group reported significantly more positive self-appraisals, reduced tension, and enhanced vigor. Bivariate and multiple regression analyses indicated that when each of the 4 self-appraisal and 2 mood factors were simultaneously entered into a regression equation, 36% of the variance in voluntary physical activity was explained. Findings support the treatment's association with theoretically based correlates of physical activity in the present sample, and suggest directions for physical activity interventions for youth. Key pointsSocial cognitive theory offers a framework for understanding correlates of physical activity in youth.This study suggests that it is possible for a convenient physical activity intervention, led by after-school care counselors with minimal training, to improve participants' self-perceptions, mood, and voluntary physical activity.Improvements in self-perceptions and mood appeared to be significantly associated with increased free-time physical activity in African American 8- to 12-year-olds.This study's findings may lead to a better understanding of physical activity promotion in youth, and foster improvements in physical activity curricula.

Age as a moderator of relations of physical self-concept and mood changes associated with 10 weeks of programmed exercise in women

Significant correlations were found between reported changes in scores on the Physical Self-concept scale of the Tennessee Self-concept Scale, with those on the Depression (r=-.34) and Total Mood Disturbance (r=-.38) scales of the Profile of Mood States, for 35 women who initiated a structured exercise program. Accounting for age in simultaneous multiple regression equations added to the explained variance in changes in both Depression (R2=.29) and Total Mood Disturbance (R2=.18) scores. Findings supported propositions of social cognitive theory and self-efficacy theory. Limitations and the need for replication and extension were discussed.

Effects of a 12-week physical activity protocol delivered by YMCA after-school counselors (Youth Fit for Life) on fitness and self-efficacy changes in 5-12-year-old boys and girls

To address reduced physical education (PE) in elementary schools, a 12-week physical activity protocol was tested on 5-12-year-old, primarily African American, girls (n = 226) and boys (n = 344) at 14 YMCA after-school care sites. The 3 times/week, 45-min session curriculum included cardiovascular, resistance, and flexibility training, in which all children could participate simultaneously, and a behavioral skills education component. After-school counselors, formerly untrained in PE methods, administered the sessions, with periodic supervision by YMCA wellness staff members. Analyses of the eight Age x Sex subsamples indicated significant improvements on body composition, strength, and endurance, both within-groups and when predicted changes due to maturation were accounted for. Exercise barriers self-efficacy significantly increased in subsamples of 9-10- and 11-12-year-old girls only. The need for replication across ethnic groups was suggested. Limitations and the need for extension of research on supplementation of elementary school PE were discussed.

Relationship of feeling states after exercise and Total Mood Disturbance over 10 weeks in formerly sedentary women

Changes in feeling states after exercise and changes in overall mood after a period of 10 weeks were correlated after participation in a supervised, moderate intensity resistance training program. 52 previously sedentary, asymptomatic women (M=56 yr.) participated. Point biserial correlations were calculated between the 10-wk. change on the Profile of Mood States using the Total Mood Disturbance score as the continuous variable, and positive or negative change in feeling states after exercise, assessed via the Exercise-induced Feeling Inventory, being the dichotomous variable. Correlations were significant for both the total sample (rpb=-.49) and participants with high initial Total Mood Disturbance based on a median split (rpb=-.55). Participants with positive changes in their feeling states after exercise also showed a significantly greater decrease in Total Mood Disturbance than those with negative changes. Changes in Total Mood Disturbance were not significantly correlated with changes in resting heart rate over the 10 weeks. Discussion included limitations and, after replication, possible application of the findings.

Maximal strength testing in healthy children

Strength training has become an accepted method of conditioning in children. However, there is concern among some observers that maximal strength testing may be inappropriate or potentially injurious to children. The purpose of this study was to evaluate the safety and efficacy of 1 repetition maximum (1RM) strength testing in healthy children. Thirty-two girls and 64 boys between 6.2 and 12.3 years of age (mean age 9.3 +/- 1.6 years) volunteered to participate in this study. All subjects were screened for medical conditions that could worsen during maximal strength testing. Under close supervision by qualified professionals, each subject performed a 1RM test on 1 upper-body (standing chest press or seated chest press) and 1 lower-body (leg press or leg extension) exercise using child-size weight training machines. No injuries occurred during the study period, and the testing protocol was well tolerated by the subjects. No gender differences were found for any upper- or lower-body strength test. These findings demonstrate that healthy children can safely perform 1RM strength tests, provided that appropriate procedures are followed.

Comparison of 1 and 2 days per week of strength training in children

The purpose of this study was to compare the effects of 1 and 2 days per week of strength training on upper body strength, lower body strength, and motor performance ability in children. Twenty-one girls and 34 boys between the ages of 7.1 and 12.3 years volunteered to participate in this study. Participants strength trained either once per week (n = 22) or twice per week (n = 20) for 8 weeks at a community-based youth fitness center. Each training session consisted of a single set of 10-15 repetitions on 12 exercises using child-size weight machines. Thirteen children who did not strength train served as age-matched controls. One repetition maximum (1RM) strength on the chest press and leg press, handgrip strength, long jump, vertical jump, and flexibility were assessed at baseline and posttraining. Only participants who strength trained twice per week made significantly greater gains in 1RM chest press strength, compared to the control group (11.5 and 4.4% respectively, p < .05). Participants who trained once and twice per week made gains in 1RM leg press strength (14.2 and 24.7%, respectively) that were significantly greater than control group gains (2.4%). On average, participants who strength trained once per week achieved 67% of the 1RM strength gains. No significant differences between groups were observed on other outcome measures. These findings support the concept that muscular strength can be improved during the childhood years and favor a training frequency of twice per week for children participating in an introductory strength training program.

Effects of different resistance training protocols on upper-body strength and endurance development in children

This study examined the effects of 4 different resistance training protocols on upper-body strength and local muscle endurance development in children. Untrained boys and girls (mean +/- SD age, 8.1 +/- 1.6 years) trained twice per week for 8 weeks using child-sized weight machines and medicine balls weighing 1-2.5 kg. In addition to general conditioning exercises, subjects in each exercise group performed 1 set of the following exercise protocols for upper-body conditioning: 6-8 repetitions with a heavy load on the chest press exercise (HL, n = 15); 13-15 repetitions with a moderate load on the chest press exercise (ML, n = 16); 6-8 repetitions with a heavy load on the chest press exercise immediately followed by 6-8 medicine ball chest passes (CX, n = 12); or 13-15 medicine ball chest passes (MB, n = 11). Twelve children served as nontraining controls (CT). After training, only the ML and CX groups demonstrated significant (p < 0.05) improvements in 1RM chest press strength (16.8% and 16.3%, respectively) as compared with the CT group. Local muscle endurance, as determined by the number of repetitions performed posttraining on the chest press exercise with the pretraining 1RM load, significantly increased in the ML group (5.9 +/- 3.2 repetitions) and CX group (5.2 +/- 3.6 repetitions) as compared with the CT group. In terms of enhancing the upper-body strength and local muscle endurance of untrained children, these findings favor the prescription of higher-repetition training protocols during the initial adaptation period.

Effects of regular and slow speed resistance training on muscle strength

BACKGROUND

The study assessed a way to increase the intensity and effectiveness of resistance training by comparing training with a slower repetition speed to training with a conventional repetition speed. Slower repetition speed may effectively increase intensity throughout the lifting phase while decreasing momentum.

METHODS

Two studies were done with untrained men (N=65) and women (N=82), (mean age=53.6) who trained two to three times per week for eight to 10 weeks on a 13 exercise Nautilus circuit performing one set of each exercise. Participants exclusively trained using regular speed repetitions for 8 to 12 repetitions per set at 7 sec each (2 sec lifting, 1 sec pause, 4 sec lowering) or a Super Slow training protocol where they completed 4 to 6 repetitions per set at 14 sec each (10 sec lifting, 4 sec lowering). All of the participants were tested for either the 10 repetition-maximum (RM) weightload (regular-speed group) or the 5-RM weightload (slow-speed group).

RESULTS

In both studies, Super-Slow training resulted in about a 50% greater increase (p<0.001) in strength for both men and women than regular speed training. In Study 1, the Super-Slow training group showed a mean increase of 12.0 kg and the regular speed group showed an increase of 8.0 kg increase (p<0.001). In Study 2, the Super-Slow training group showed a 10.9 kg increase and the regular speed group showed an increase of 7.1 kg (p<0.001).

CONCLUSIONS

Super-Slow training is an effective method for middle-aged and older adults to increase strength. Although studies still need to be done with at-risk populations, repetition speed should be considered when prescribing resistance training.

The effects of different resistance training protocols on muscular strength and endurance development in children

BACKGROUND

Previous research has shown that children can increase their muscular strength and muscular endurance as a result of regular participation in a progressive resistance training program. However, the most effective exercise prescription regarding the number of repetitions remains questionable.

OBJECTIVE

To compare the effects of a low repetition-heavy load resistance training program and a high repetition-moderate load resistance training program on the development of muscular strength and muscular endurance in children. Design. Prospective, controlled trial.

SETTING

Community-based youth fitness center.

SUBJECTS

Eleven girls and 32 boys between the ages of 5.2 and 11.8 years.

INTERVENTION

In twice-weekly sessions of resistance training for 8 weeks, children performed 1 set of 6 to 8 repetitions with a heavy load (n = 15) or 1 set of 13 to 15 repetitions with a moderate load (n = 16) on child-size exercise machines. Children in the control group (n = 12) did not resistance train. One repetition maximum (RM) strength and muscular endurance (repetitions performed posttraining with the pretraining 1-RM load) were determined on the leg extension and chest press exercises.

RESULTS

One RM leg extension strength significantly increased in both exercise groups compared with that in the control subjects. Increases of 31.0% and 40.9%, respectively, for the low repetition-heavy load and high repetition-moderate load groups were observed. Leg extension muscular endurance significantly increased in both exercise groups compared with that in the control subjects, although gains resulting from high repetition-moderate load training (13.1 +/- 6.2 repetitions) were significantly greater than those resulting from low repetition-heavy load training (8.7 +/- 2.9 repetitions). On the chest press exercise, only the high repetition-moderate load exercise group made gains in 1-RM strength (16.3%) and muscular endurance (5.2 +/- 3.6 repetitions) that were significantly greater than gains in the control subjects.

CONCLUSION

These findings support the concept that muscular strength and muscular endurance can be improved during the childhood years and favor the prescription of higher repetition-moderate load resistance training programs during the initial adaptation period.

Strength and bite, Part 2: Testing isometric strength using a MORA set to a functional criterion

The effect on isometric strength of biting on three intraoral devices and habitual occlusion was analyzed. Only subjects who showed a relative weakness to the Isometric Deltoid Press (IDP) when biting as opposed to maintaining the mandible in an unsupported rest position were included in the study. Both in the original 35 subjects and the 23 subjects returning on the second day, performance wearing the appliance set by a functional criterion of peak strength (locking) to the IDP was significantly greater than wearing a placebo appliance and a bite raising appliance that deflected the mandible 1 mm to the left. Strength biting on the appliance set by a functional criterion was significantly greater than all these conditions. Strength biting in habitual trials that were matched with the deflection condition was found to be significantly greater than that biting in the placebo condition. It was concluded that a relationship does exist between bite and isometric strength. Previous speculation about the role of placebo effect was not substantiated by the data gathered in this experiment.

Strength and bite, Part 1: An analytical review

The original clinical observations and research in the area of bite and strength enhancement studied individuals with obvious malocclusion and a subject population with mixed occlusions. An increase in isometric strength was obtained when biting on a K-MORA, an intraoral device that supports a mandibular position determined by a functional criterion. The criterion is a locking response to the Isometric Deltoid Press, a muscle challenge used by kinesiologists. Rather than replication with improved design, subsequent research (1) employed different mandibular positions based on therapeutic, electrical impulse or structural criteria; (2) tested mainly isokinetic strength; (3) referred to "strength" without qualification, implying more generalization than the findings actually allowed; (4) criticized and rejected positive findings by attributing strength increase to the placebo effect even though in no instance has the placebo effect been demonstrated in this field. Considering published and unpublished research on isometric strength and the irrelevance of many studies that found no difference in isokinetic strength, it is concluded that it is most probable that isometric strength is increased by the K-MORA in mixed populations.