Dirk Lauber

Differential effects of strength versus power training on bone mineral density in postmenopausal women: a 2-year longitudinal study

Objectives: To investigate the effect of two different schemes of loading in resistance training on bone mineral density (BMD) and pain in pretrained postmenopausal women. Methods: 53 pretrained women (mean (SD) age 58.2 (3.7) years) who carried out a mixed resistance and gymnastics programme were randomly assigned to a strength training (ST) or power training (PT) group. The difference between the two groups was the movement velocity during the resistance training (ST, 4 s (concentric)/4 s (eccentric); PT, explosive/4 s). Otherwise both groups carried out periodised progressive resistance training (10–12 exercises, 2–4 sets, 4–12 repetitions at 70–92.5% of the one-repetition maximum (2/week) for 2 years. Mechanical loading was determined with a force measuring plate during the leg press exercise. At baseline and after 2 years, BMD was measured at different sites with dual x-ray absorptiometry. Pain was assessed by questionnaire. Results: Loading magnitude, loading/unloading rate, loading amplitude and loading frequency differed significantly (p<0.001) between the two groups. After 2 years, significant between-group differences were detected for BMD (PT, −0.3%; ST, −2.4%; p<0.05) and bone area (PT, 0.4%; ST, −0.9%; p<0.05) at the lumbar spine. At the hip, there was a non-significant trend in favour of the PT group. Also the incidence of pain indicators at the lumbar spine was more favourable in the PT group. Conclusion: The results show that PT may be superior for maintaining BMD in postmenopausal women. Furthermore, PT was safe as it did not lead to increased injury or pain.

Exercise effects on menopausal risk factors of early postmenopausal women: 3-yr Erlangen fitness osteoporosis prevention study results.

PURPOSE To determine the impact of multipurpose exercise training on bone, body composition, blood lipids, physical fitness, and menopausal symptoms in early postmenopausal women with osteopenia. METHODS Forty-eight fully compliant (more than two sessions per week for 38 months) women (55.1 +/- 3.3 yr) without any medication or illness affecting bone metabolism took part in the exercise training (EG); 30 women (55.5 +/- 3.0 yr) served as the nontraining control group (CG). Both groups were individually supplemented with calcium and vitamin D. Bone mineral density (BMD) at various sites (lumbar spine, hip, forearm, calcaneus) was measured by dual x-ray absorptiometry (DXA) and quantitative ultrasound (QUS). Maximal isometric and dynamic strength, maximal oxygen consumption (VO(2max)), CHD risk factors (blood lipids, body composition), and menopausal symptoms were determined. RESULTS After 38 months, significant differences between EG and CG were observed for the BMD at the lumbar spine (0.7% vs -3.0%) and the femoral neck (-0.7% vs -2.6%), body composition (waist circumference, waist-to-hip ratio), blood lipids (total cholesterol, triglycerides), and menopausal symptoms (insomnia, migraines, mood changes). Maximal isometric strength increased significantly by 10-36% in the EG, whereas, with one exception, changes in the CG were all negative. One-repetition maximum increased significantly at all sites measured (15-43%, P < 0.001). VO(2max) of the EG increased throughout the study with a significant 13.9 +/- 15.6% net increase after 3 yr. No significant changes after 3 yr could be observed in the CG. CONCLUSIONS Our mixed high-intensity exercise program effectively compensates for most negative changes related to the menopausal transition.

Effects of single- vs. multiple-set resistance training on maximum strength and body composition in trained postmenopausal women.

The purpose of this study was to examine the effect of a single- vs. a multiple-set resistance training protocol in well-trained early postmenopausal women. Subjects (N = 71) were randomly assigned to begin either with 12 weeks of the single-set or 12 weeks of the multiple-set protocol. After another 5 weeks of regenerational resistance training, the subgroup performing the single-set protocol during the first 12 weeks crossed over to the 12-week multiple-set protocol and vice versa. Neither exercise type nor exercise intensity, degree of fatigue, rest periods, speed of movement, training sessions per week, compliance and attendance, or periodization strategy differed between exercise protocols. Body mass, body composition, and 1 repetition maximum (1RM) values for leg press, bench press, rowing, and leg adduction were measured at baseline and after each period. Multiple-set training resulted in significant increases (3.5–5.5%) for all 4 strength measurements, whereas single-set training resulted in significant decreases (21.1 to 22.0%). Body mass and body composition did not change during the study. The results show that, in pretrained subjects, multiple-set protocols are superior to single-set protocols in increasing maximum strength.

ACCURACY OF PREDICTION EQUATIONS FOR DETERMINING ONE REPETITION MAXIMUM BENCH PRESS IN WOMEN BEFORE AND AFTER RESISTANCE TRAINING

Mayhew, JL, Johnson, BD, LaMonte, MJ, Lauber, D, and Kemmler, W. Accuracy of prediction equations for determining one repetition maximum bench press in women before and after resistance training. J Strength Cond Res 22(5): 1570-1577, 2008-Repetitions to fatigue (RTF) using less than a 1 repetition maximum (1RM) load (RepWt) have been shown to be a good predictor of 1RM strength in men, but such information is scarce in women. The purpose of this study was to evaluate the accuracy of current prediction equations to estimate 1RM bench press performance and to determine whether resistance training changes the capability to predict 1RM from muscular endurance repetitions in young women. Members (n = 103) of a required wellness course were measured for 1RM bench press and RTF using randomly assigned percentages between 60% and 90% of the 1RM (RepWt) before and after 12 weeks of progressive resistance training. The %1RM used to perform RTF remained the same for each individual after training (75.6% ± 10.3%) as before. One repetition maximum bench press increased significantly after training (28% ± 21%). Although the change in the group average for RTF (0.6 ± 6.1) was not significant, the correlation between pretraining and posttraining RTF was moderate (r = 0.66; p < 0.01), and individual differences in percentage change in RTF were substantial (27% ± 99%). The percentage change in 1RM was not significantly related to initial 1RM (r = −0.05), but it was negatively related to the change in RTF (r = −0.40; p < 0.01). Prediction equations were more accurate in the pretraining and posttraining conditions, in which fewer than 10 RTF were used. Resistance training may alter the relationship between strength and muscle endurance across a wide range of RTF in young women without compromising the accuracy of predicting maximal strength.

Long-term four-year exercise has a positive effect on menopausal risk factors: the Erlangen Fitness Osteoporosis Prevention Study.

The purpose of the study was to determine the effect of long-term exercise on coronary heart disease, osteoporotic risk factors, and physical fitness parameters in postmenopausal women. Forty early postmenopausal women (age 55.1 ± 3.3 years) with no medication or illness affecting bone metabolism exercised (high impact aerobic, multilateral jumps, multi-set resistance exercise) for 50 months (EG), while 28 women (age 55.5 ± 3.0 years) served as a nontraining control (CG). Both groups were supplemented with calcium and cholecalciferol. Bone mineral density (BMD) was measured at the lumbar spine, hip, and forearm by dual energy x-ray absorptiometry. Blood lipids were determined using serum samples, and body composition was determined using the bioimpedance technique. Further, maximum isometric strength was determined (Schnell M3, Schnell Trainer). The BMD at the lumbar spine (+1.0%, p = 0.037) and the total hip (−0.3%, p = 0.194) were maintained in the EG, while significant (p < 0.001) decreases were observed in the CG (lumbar spine −3.2; total hip −2.3%). Differences between both groups were significant (p < 0.001). Significant differences between EG and CG were also observed, respectively, for total cholesterol (−6.1 vs. +3.5%, p = 0.008), HDL-cholesterol (+14.1 vs. −7.1%, p = 0.007), triglycerides (−10.2 vs. +27.5%, p = 0.002), body fat (−3.3 vs. +1.3%, p = 0.041), and waist-hip-ratio (−3.5 vs. +0.2%, p > 0.001). Maximum isometric strength significantly (p < 0.001) increased in the EG, while strength parameters decreased in the CG (−0.5 to −6.4%). Thus, the study demonstrated that multipurpose high-intensity exercise programs significantly affect relevant menopausal risk factors and, therefore, may be individually considered as an alternative to hormone replacement therapy.

PREDICTING MAXIMAL STRENGTH IN TRAINED POSTMENOPAUSAL WOMAN

The purpose of this study was to present an equation that accurately predicts 1 repetition maximum (RM) over a wide range of repetitions to fatigue (RTF) for 4 different machine resistance exercises in postmenopausal women. Seventy trained women (age = 57.4 ± 3.1 years) performed maximal and submaximal repetitions on leg press, bench press, rowing, and leg adduction machines at the conclusion of a 2-year training program. Maximal repetitions were performed on each exercise in the following ranges: 3–5RM, 6–10RM, 11–15RM, and 16–20RM. Special regard was taken to maintain the identical execution of each test (i.e., range of motion, starting angle, speed of movement). One cubic polynomial (wi [0.988–0.0000584 ri3 + 0.00190 ri2 + 0.0104 ri,] where wi is the load of measurement I, and ri is the number of repetitions) accurately predicted 1RM from RTF with mean absolute differences between actual 1RM and predicted 1RM for the 4 exercises of 1.5–3.1% and with coefficients of variation of <3.3%. Equation accuracy was independent of the exercise type or the number of RTF. Thus, this study supported the validity of RTF to adequately estimate 1RM over a wide range of repetitions and within different exercises in trained, older female subjects.

Impact of testing strategy on expression of upper-body work capacity and one-repetition maximum prediction after resistance training in college-aged men and women.

Mayhew, JL, Brechue, WF, Smith, AE, Kemmler, W, Lauber, D, and Koch, AJ. Impact of testing strategy on expression of upper-body work capacity and one repetition maximum prediction after resistance training in college-aged men and women. J Strength Cond Res 25(10): 2796–2807, 2011—The purpose of this study was to assess the effect of resistance training on upper-body muscular strength and the expression of work capacity and muscular endurance. In addition, a training-induced change in the relationship between muscular strength and endurance was assessed by testing changes in the accuracy of using endurance repetitions to predict 1 repetition maximum (1RM) bench press before and after training. College-aged men (n = 85) and women (n = 62) completed a 12-week linear periodization resistance training program. Before and after training, the subjects were assessed for 1RM and repetitions to fatigue (RTFs) with a submaximal load. After pretraining 1RM determination, the subjects were randomly assigned to perform RTFs at 65% 1RM (n = 74) or 90% 1RM (n = 73). Pretraining and posttraining RTFs were conducted at the same respective %1RM. Work capacity was determined from repetition weight × RTF. After training, there was a significant increase in 1RM in both men (∼14%) and women (∼23%). Posttraining RTF was not different from pretraining RTF at 65 %1RM (18.2 ± 5.1 and 19.0 ± 6.0, respectively) but was significantly reduced in the 90% 1RM group (6.1 ± 3.6 vs. 4.5 ± 2.7, respectively). Likewise, there was a differential effect of training on the expression of work capacity, which increased in the 65 %1RM group (123 ± 155 kg-reps) but decreased in the 90% 1RM group (−62 ± 208 kg-reps); the effect was independent of gender within each testing group. In conclusion, the changes in muscular strength associated with resistance training produced an increase in work capacity when tested with a 65 %1RM load without a change in endurance. In contrast, both work capacity and endurance decreased when tested with 90% 1RM. Thus, the impact of strength training on work capacity and muscle endurance is specific to the load at which endurance testing is performed.