J. David Taylor

Reliability of the 8-repetition maximum test in men and women

OBJECTIVE The 8-repetition maximum test has been recommended as a method of prescribing an intensity for resistance training in healthy adults, athletes, and patients with health conditions. Yet, limited research related to the reliability of 8-repetition maximum testing has been conducted. The purpose of this study was to determine the reliability of the 8-repetition maximum test in men and women. DESIGN Test-retest reliability study. METHODS Twenty-eight people (14 males, 14 females, mean age=23.0 years [standard deviation=1.3]) with no exercise contraindications participated in this study. After familiarization, each participant underwent 8-repetition maximum testing using 4 different exercises. For all participants, the 8-repetition maximum test was performed during 2 sessions with 2-3 days between sessions. The intraclass correlation coefficient (ICC([1,2])), typical error as the coefficient of variation (TE(CV)), and the Bland-Altman plot were used to assess reliability. Unpaired t-test was used to determine the influence of gender on differences between initial test and retest values. RESULTS Excellent reliability of the 8-repetition maximum test was found for all exercises (ICC([1,2])>0.9). The range of TE(CV) values was 3.4-10.4%. The Bland-Altman plot illustrated that 27 out of 28 data points for total 8-repetition maximum scores were within the 95% limits of agreement. Unpaired t-test indicated no significant difference between men and women in variations between initial test and retest 8-repetition maximum scores. CONCLUSION The findings of this study suggest that an 8-repetition maximum test protocol that includes familiarization is reliable in men and women.

Impact of Physical Therapist–Directed Exercise Counseling Combined With Fitness Center–Based Exercise Training on Muscular Strength and Exercise Capacity in People With Type 2 Diabetes: A Randomized Clinical Trial

Background: Assessing muscular strength (force-generating capacity) and exercise capacity in response to an intervention for people with type 2 diabetes is clinically important in the prevention of type 2 diabetes-related complications. Objective: The purpose of this study was to investigate the impact of physical therapist–directed exercise counseling combined with fitness center–based exercise training on muscular strength and exercise capacity in people with type 2 diabetes. Design: This study was a randomized clinical trial. Setting: The study was conducted on a university campus, with patient recruitment from the local community. Patients: Twenty-four people with type 2 diabetes were randomly allocated to either a group that received physical therapist–directed exercise counseling plus fitness center–based exercise training (experimental group) or a group that received laboratory-based, supervised exercise (comparison group). Intervention: The experimental group received physical therapist–directed exercise counseling on an exercise program and was provided access to a fitness center. The comparison group received the same exercise program as the experimental group while under supervision. Measurements: For all participants, chest press, row, and leg press muscular strength (1-repetition maximum [in kilograms]) and exercise capacity (graded exercise test duration [in minutes]) testing were conducted at baseline and 2 months later. Results: No significant differences in improvements in muscular strength were found for the chest press (adjusted mean difference=1.2; 95% confidence interval [CI]=−5.5 to 7.8), row (adjusted mean difference=0.1; 95% CI=−9.0 to 9.1), or leg press (adjusted mean difference=2.7; 95% CI=−9.1 to 14.6) between the groups. No significant difference in improvement in exercise capacity (adjusted mean difference=0.2; 95% CI=−0.9 to 1.2) was found between the groups. Limitations: Lack of group allocation blinding and the small sample size were limitations of this study. Conclusions: The results suggest that physical therapist–directed exercise counseling combined with fitness center–based exercise training can improve muscular strength and exercise capacity in people with type 2 diabetes, with outcomes comparable to those of supervised exercise.

Intrarater reliability of 1 repetition maximum estimation in determining shoulder internal rotation muscle strength performance.

The purpose of this study was to determine intrarater reliability of the 1 repetition maximum (1RM) estimation for shoulder internal rotation. The accuracy of the estimated 1RM was determined by establishing the actual 1RM. Fifteen subjects were positioned supine with the shoulder in 08 abduction (position 1) and prone with the shoulder in 908 abduction (position 2). Subjects were placed in both testing positions and performed resisted shoulder internal rotation. A 1RM estimation equation was used to estimate shoulder internal rotation strength. After 1 week, procedures were repeated and intrarater reliability was calculated. One week after 1RM estimation procedures were completed, the accuracy of an estimated 1RM was determined by establishing an actual 1RM. The results indicated excellent intrarater reliability for position 1 (intraclass correlation coefficient [ICC] = 0.99) and position 2 (ICC = 0.96). The correlation coefficients for accuracy indicated excellent concurrent validation was attained for position 1 (ICC = 0.99) and position 2 (ICC = 0.97). Shoulder internal rotation 1RM estimation appears to be reliable and accurate. Clinicians may use submaximal loads to estimate the 1RM and decrease the possibility of injury during actual 1RM strength testing.

Correlation between the 8-repetition maximum test and isokinetic dynamometry in the measurement of muscle strength of the knee extensors: A concurrent validity study

The 8-repetition maximum test has the potential to be a feasible, cost-effective method of measuring muscle strength for clinicians. The purpose of this study was to investigate the concurrent validity of the 8-repetition maximum test in the measurement of muscle strength by comparing the 8-repetition maximum test to the gold standard of isokinetic dynamometry. Thirty participants (15 males and 15 females, mean age = 23.2 years [standard deviation = 1.0]) underwent 8-repetition maximum testing and isokinetic dynamometry testing of the knee extensors (at 60, 120, and 240 degrees per second) on two separate sessions with 2–3 days between each mode of testing. Linear regression was used to assess the validity by comparing the findings between 8-repetition maximum testing and isokinetic dynamometry testing. Significant correlations were found between the 8-repetition maximum and isokinetic dynamometry peak torque at each testing velocity (r  =  0.71–0.85). The highest correlations were between the 8-repetition maximum and isokinetic dynamometry peak torques at 60 (r  =  0.85) and 120 (r  =  0.85) degrees per second. The findings of this study provide supportive evidence for the use of 8-repetition maximum testing as a valid, alternative method for measuring muscle strength.

Effects of Moderate- Versus High-Intensity Exercise Training on Physical Fitness and Physical Function in People With Type 2 Diabetes: A Randomized Clinical Trial

Background Exercise training is effective for improving physical fitness and physical function in people with type 2 diabetes. However, limited research has been conducted on the optimal exercise training intensity for this population. Objective The primary study objective was to investigate the effects of moderate- versus high-intensity exercise training on physical fitness and physical function in people with type 2 diabetes. Design This was a randomized clinical trial. Setting The setting was a university campus. Participants Twenty-one people with type 2 diabetes were randomly allocated to receive either moderate-intensity training (MOD group) or high-intensity training (HIGH group). Intervention The MOD group performed resistance training at an intensity of 75% of the 8-repetition maximum (8-RM) and aerobic training at an intensity of 30% to 45% of the heart rate reserve (HRR). The HIGH group performed resistance training at an intensity of 100% of the 8-RM and aerobic training at an intensity of 50% to 65% of the HRR. Measurements Muscle strength (peak torque [newton-meters]), exercise capacity (graded exercise test duration [minutes]), and physical function (Patient-Specific Functional Scale questionnaire) were measured at baseline and 3 months later. Acute exercise-induced changes in glucose levels were assessed immediately before exercise, immediately after exercise, and 1 hour after exercise during the first exercise training session. Results Although both groups showed improvements in physical fitness and physical function, the between-group effect sizes were not statistically significant (exercise capacity estimated marginal mean [EMM] difference=2.1, 95% confidence interval [95% CI]=−0.2, 4.5; muscle strength EMM difference=20.8, 95% CI=−23.3, 65.0; and physical function EMM difference=0.1, 95% CI=−0.6, 0.9). Mean percent changes in glucose levels measured immediately before exercise and immediately after exercise, immediately after exercise and 1 hour after exercise, and immediately before exercise and 1 hour after exercise for the MOD group were −11.4%, −5.0%, and −15.8%, respectively; those for the HIGH group were −21.5%, 7.9%, and −15.3%, respectively. Limitations Sample size, lack of outcome assessor masking, and physical function measurement subjectivity were limitations. Conclusions Moderate- and high-intensity exercise training, as defined in this study, may lead to similar improvements in physical fitness and physical function in people with type 2 diabetes.

The impact of a supervised strength and aerobic training program on muscular strength and aerobic capacity in individuals with type 2 diabetes.

An intervention in the clinical management of individuals with type 2 diabetes is strength and aerobic training. Limited research has been conducted that investigates the effect of a supervised strength and aerobic training program on muscular strength and aerobic capacity in people with type 2 diabetes. The purpose of this 1-group repeated-measures–designed study was to investigate the impact of a supervised strength and aerobic training program on muscular strength and aerobic capacity in subjects with type 2 diabetes. Thirteen subjects with type 2 diabetes completed the training program. Subjects met the American Diabetes Association diagnostic criteria for type 2 diabetes. For each subject, muscular strength (estimated 1 repetition maximum) and aerobic capacity (esti- mated maximal oxygen uptake) were measured before and after a supervised strength and aerobic training program as well as during a 6-week follow-up. Repeated-measures analysis of variance was used to compare muscular strength and aerobic capacity between pretesting, posttesting, and follow-up testing periods. Significant improvements in muscular strength (p > 0.01) and aerobic capacity (p > 0.01) were found during posttesting and follow-up testing, as compared to pretesting measures. Yet a significant loss in muscular strength (p > 0.01) and no significant change in aerobic capacity (p > 0.05) were found during follow-up testing, as compared to posttesting measures. This study indicates that a supervised strength and aerobic training program can significantly improve muscular strength and aerobic capacity in people with type 2 diabetes. Yet improvements in muscular strength due to training will not be maintained if individuals with type 2 diabetes do not adhere to a continuous training program. In addition, aerobic capacity can be improved with training, but aerobic capacity will not continue to improve if people with type 2 diabetes are not compliant with a continuous training program.

The impact of electronic mail versus print delivery of an exercise program on muscular strength and aerobic capacity in people with type 2 diabetes.

Taylor, JD. The impact of electronic mail versus print delivery of an exercise program on muscular strength and aerobic capacity in people with type 2 diabetes. J Strength Cond Res 22(5): 1696-1704, 2008-Previous research indicates that the Internet, electronic mail (e-mail), and printed materials can be used to deliver interventions to improve physical activity in people with type 2 diabetes. However, no studies have been conducted investigating the effect of e-mail or print delivery of an exercise program on muscular strength and aerobic capacity in people with type 2 diabetes. The purpose of this clinical trial was to investigate the impact of e-mail vs. print delivery of an exercise program on muscular strength and aerobic capacity in people with type 2 diabetes. Nineteen participants with type 2 diabetes were allocated to either a group that was delivered a prescribed exercise program using e-mail (e-mail group, n = 10) or a group that was delivered the same prescribed exercise program in print form (print group, n = 9). Chest press and leg press estimated one-repetition maximum (1-RM) scores as well as estimated peak oxygen uptake (&OV0312;O2peak) were measured at baseline and follow-up. Intention-to-treat analysis indicated significant improvements in chest press (mean = 7.00 kg, p = 0.001, effect size = 2.22) and leg press (mean = 19.32 kg, p = 0.002, effect size = 1.98) 1-RM scores and &OV0312;O2peak (mean = 9.38 mL of oxygen uptake per kilogram of body mass per minute, p = 0.01, effect size = 1.45) within the e-mail group. Within the print group, significant improvements in chest press (mean = 9.13 kg, p = 0.01, effect size = 1.49) and leg press (mean = 16.68 kg, p = 0.01, effect size = 1.31) 1-RM scores and &OV0312;O2peak (mean = 5.14 ml of oxygen uptake per kilogram of body mass per minute, p = 0.03, effect size = 1.14) were found. No significant between-group differences in improvements were found. Clinicians can deliver a prescribed exercise program, either by e-mail or in print form, to significantly improve muscular strength and aerobic capacity in people with type 2 diabetes, and expect similar outcomes.