Prediction of one repetition maximum strength from multiple repetition maximum testing and anthropometry

The purpose of this study was to quantify the decrease in the load lifted from 1 to 5, 10, and 20 repetitions to failure for the flat barbell bench press (chest press; CP) and plate-loaded leg press (LP). Furthermore, we developed prediction equations for 1 repetition maximum (RM) strength from the multiple RM tests, including anthropometric data, gender, age, and resistance training volume. Seventy subjects (34 men, 36 women), 18-69 years of age, completed 1, 5, 10, and 20RM testing for each of the CPs and LPs. Regression analyses of mean data revealed a nonlinear decrease in load with increasing repetition number (CP: linear S(y.x) = 2.6 kg, nonlinear S(y.x) = 0.2 kg; LP: linear S(y.x) = 11.0 kg, nonlinear S(y.x) = 2.6 kg, respectively). Multiple regression analyses revealed that the 5RM data produced the greatest prediction accuracy, with R(2) data for 5, 10, and 20RM conditions being LP: 0.974, 0.933, 0.915; CP: 0.993, 0.976, and 0.955, respectively. The regression prediction equations for 1RM strength from 5RM data were LP: 1RM = 1.0970 x (5RM weight [kg]) + 14.2546, S(y.x) = 16.16 kg, R(2) = 0.974; CP: 1RM = 1.1307 x (5RM weight) + 0.6999, S(y.x) = 2.98 kg, R(2) = 0.993. Dynamic muscular strength (1RM) can be accurately estimated from multiple repetition testing. Data reveal that no more than 10 repetitions should be used in linear equations to estimate 1RM for the LP and CP actions.     

Specificity of training modalities on upper-body one repetition maximum performance: free weights vs. hammer strength equipment

The purpose of this study was to determine whether a relationship exists between 1-repetition maximum (1RM) performed on hammer strength (HS) machines compared to free weights (FWs) and also to develop regression equations that can accurately predict 1RM when switching from exercise modality to another. Thirty-one trained male subjects performed 1-RM lifts (1RM's) on 3 HS externally loaded machines and 3 comparable FW exercises. Subjects performed 2 1RM tests during each laboratory session, with at least 48-72 hours of recovery between each. One repetition maximum data were used to (a) determine the relationship between 1RM performed on HS vs. FW and (b) to develop regression equations that can accurately predict 1RM's when switching from 1 exercise modality to another. Statistics revealed significant differences (p < 0.05) between 1RM's performed on the HS equipment as compared to its corresponding (FW) exercise. For all exercises, 1RM's were significantly greater on the HS equipment. Regression equations were developed for all exercises, except when predicting the HS shoulder press and the HS preacher curls from their free weight counterparts, where no variables existed that could significantly predict their respective 1RM's. As 1 RMs were significantly greater when using the HS equipment compared to when using FWs, those transitioning from HS exercise to FW exercise should exercise caution.     

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 0 degrees abduction (position 1) and prone with the shoulder in 90 degrees 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.     

Maximal power at different percentages of one repetition maximum: influence of resistance and gender

National Collegiate Athletic Association Division I athletes were tested to determine the load at which maximal mechanical output is achieved. Athletes performed power testing at 30, 40, 50, 60, and 70% of individual 1 repetition maximum (1RM) in the squat jump, bench press, and hang pull exercises. Additionally, hang pull power testing was performed using free-form (i.e., barbell) and fixed-form (i.e., Smith machine) techniques. There were differences between genders in optimal power output during the squat jump (30-40% of 1RM for men; 30-50% of 1RM for women) and bench throw (30% of 1RM for men; 30-50% of 1RM for women) exercises. There were no gender or form interactions during the hang pull exercise; maximal power output during the hang pull occurred at 30-60% of 1RM. In conclusion, these results indicate that (a) gender differences exist in the load at which maximal power output occurs during the squat jump and bench throw; and (b) although no gender or form interactions occurred during the hang pull exercise, greater power could be generated during fixed-form exercise. In general, 30% of 1RM will elicit peak power outputs for both genders and all exercises used in this study, allowing this standard percentage to be used as a starting point in order to train maximal mechanical power output capabilities in these lifts in strength trained athletes.     

Intra- and interrater reliability of the establishment of one repetition maximum on squat and seated knee extension

The purpose of the present study was to develop a systematic procedure for the establishment of 1 repetition maximum (1RM) in order to describe an easily accessible test procedure that is applicable for physical therapists and athletic trainers who manage strength training for healthy individuals and patients. Another purpose was to investigate the intra- and interrater reliability of 1RM of squat on 1 leg and seated knee extension on 1 leg. Estimates of leg strength and ratings of perceived exertion formed the basis of the amount of load selected. The reliability of the procedure was assessed by a test-retest design. One RM was established for 16 and 27 healthy individuals, for squat and knee extension, respectively. The intrarater reliability of 1RM of squat on 1 leg was questionable (intraclass correlation [ICC] 0.64, measurement error 13.1 kg). The interrater reliability of 1RM of squat on 1 leg was clinically acceptable (ICC 0.94, measurement error 5.2 kg). The intrarater and interrater reliability of 1RM of seated knee extension on 1 leg was clinically acceptable (ICC 0.90, measurement error 5.1 kg and ICC 0.96, measurement error 3.2 kg, respectively). In conclusion, both exercises can be used to determine the load in exercise programs. In addition, seated knee extension may be used to evaluate strength. In contrast, squat on 1 leg is more uncertain to use at assessments between different days, which may be due to the complexity of this exercise. The test, performed in the described manner, is suitable for physical therapists, athletic trainers, and strength and conditioning coaches in clinical practice working with strength training and rehabilitation.     

Accuracy of prediction equations for determining one repetition maximum bench press in women before and after resistance training

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.     

A modified YMCA bench press test as a predictor of 1 repetition maximum bench press strength

This study evaluated the influence of cadence on the Young Men's Christian Association (YMCA) bench press test for predicting 1 repetition maximum (1RM) bench press test performance. Fifty-eight medical students (37 men, 21 women) were evaluated for anthropometric variables (age, height, weight, fat-free mass, and percent fat), 1RM bench press, and 2 cadence tests of muscular endurance performed at cadences of 30 and 60 repetitions per minute (reps.min(-1)). Each test was performed on a separate day, with 5 days rest in between. There was no significant difference among the number of repetitions performed at each cadence by men, whereas women performed significantly more repetitions at the slower cadence. Repetitions at either cadence were good predictors of 1RM bench press in both genders (men: 30 reps.min(-1), r(2) = 0.757, standard error of the estimate [SEE] = 8.0 kg; 60 reps.min(-1), r(2) = 0.884, SEE = 8.2 kg; women: 30 reps.min(-1), r(2) = 0.754, SEE = 3.1 kg; 60 reps.min(-1), r(2) = 0.816, SEE = 2.7 kg). The addition of anthropometric dimensions to the regression equations did not improve predictive accuracy. Using both fast and slow cadences, the YMCA bench press test can provide a valid estimation of 1RM performance in untrained young men and women.     

Anthropometric dimensions do not enhance one repetition maximum prediction from the NFL-225 test in college football players

The purpose of this study was to evaluate the contribution of anthropometric dimensions to improving the accuracy of repetitions-to-fatigue (RTF) using an absolute load of 225 lbs to predict 1 repetition maximum (1RM) bench press performance in college football players. Sixty-one players from an NCAA Division II team were evaluated for 1RM bench press performance, RTF using an absolute load of 225 lbs, and measured (5 skinfolds, 2 skeletal length, and 2 muscle circumferences). Anthropometric dimensions (percent fat, lean body mass, and arm cross-sectional areas) were derived at the conclusion of 8 weeks of heavy resistance training during the off-season. None of the anthropometric dimensions made a significant additional contribution to RTF (r = 0.96, SEE = 12.3 lbs) for predicting 1RM. Of the currently available NFL-225 prediction equations found in the literature nonsignificantly underestimated 1RM from RTF by an average of 1.1 lbs (+/-12.7 lbs), whereas 5 other RTF equations significantly overpredicted by 3.5-9.0 lbs (+/-12.2-14.1 lbs). Anthropometric dimensions neither reduced the error associated with prediction of 1RM bench press using the NFL-225 test in college football players nor do they explain why some players are significantly over- or underpredicted when using muscle endurance repetitions.     

Prediction of 1 repetition maximum in high-school power lifters

Eighteen elite male power lifters performed 1-repetition maximum (1RM) and submaximal strength tests (70, 80, and 90% 1RM) to develop prediction equations for the squat (SQ), bench press (BP), and deadlift (DL) exercises. For each equation, stepwise multiple-regression prediction procedure included the maximum number of repetitions (REPS) completed at a given %1RM weight (REPWT). For SQ and BP the 70% 1RM yielded the best 1RM prediction equations: (1RM SQ [kg]) = 159.9 + (0.103 x REPS x REPWT) + (-11.552 x REPS), with a standard error of the estimate (SEE) of 5.06 kg; (1RM BP [kg]) = 90.66 + (0.085 x REPS x REPWT) + (-5.306 x REPS), with an SEE of 2.69 kg. For DL the 80% 1RM yielded the best prediction equation: (1RM DL [kg]) = 156.08 + (0.098 x REPS x REPWT) + (-12.106 x REPS), with an SEE of 4.97 kg. The athlete's years lifted (number of years of power lifting experience) was highly correlated with the 1RM strength for BP and DL (r > 0.70) but not for SQ (r < 0.70). No bodily structural dimension variable had a significant correlation with 1RM strength (r < 0.70). The results of this study indicate that 1RM SQ, BP, and DL may be predicted with an acceptable degree of accuracy in elite male high-school power lifter subjects.     

Age and sex related changes of plasma membrane fluidity in isolated rat hepatocytes

The influence of sex and age on membrane fluidity, has been investigated in 6, 12, 18 weeks old Sprague-Dawley rats. Fluorescence polarization (P) was determined at 37 degrees C with a Perkin Elmer MPF 44A fluorescence spectrophotometer. The fluorescent probe TMA-DPH was added to isolated hepatocytes prepared by collagenase method. The membrane fluidity was constantly lower in males than in females, but the difference was statistically significant only in the 12 weeks old group. Major differences appeared related to aging with a significant age-related decrease in fluidity in all animals.     

Relationship between the number of repetitions and selected percentages of one repetition maximum in free weight exercises in trained and untrained men

Resistance exercise intensity is commonly prescribed as a percent of 1 repetition maximum (1RM). However, the relationship between percent 1RM and the number of repetitions allowed remains poorly studied, especially using free weight exercises. The purpose of this study was to determine the maximal number of repetitions that trained (T) and untrained (UT) men can perform during free weight exercises at various percentages of 1RM. Eight T and 8 UT men were tested for 1RM strength. Then, subjects performed 1 set to failure at 60, 80, and 90% of 1RM in the back squat, bench press, and arm curl in a randomized, balanced design. There was a significant (p < 0.05) intensity x exercise interaction. More repetitions were performed during the back squat than the bench press or arm curl at 60% 1RM for T and UT. At 80 and 90% 1RM, there were significant differences between the back squat and other exercises; however, differences were much less pronounced. No differences in number of repetitions performed at a given exercise intensity were noted between T and UT (except during bench press at 90% 1RM). In conclusion, the number of repetitions performed at a given percent of 1RM is influenced by the amount of muscle mass used during the exercise, as more repetitions can be performed during the back squat than either the bench press or arm curl. Training status of the individual has a minimal impact on the number of repetitions performed at relative exercise intensity.     

Age and sex affect quantitative genetic parameters for dominance rank and aggression in free‐living greylag geese

Knowledge of the genetic and environmental influences on a character is pivotal for understanding evolutionary changes in quantitative traits in natural populations. Dominance and aggression are ubiquitous traits that are selectively advantageous in many animal societies and have the potential to impact the evolutionary trajectory of animal populations. Here we provide age‐ and sex‐specific estimates of additive genetic and environmental components of variance for dominance rank and aggression rate in a free‐living, human‐habituated bird population subject to natural selection. We use a long‐term data set on individually marked greylag geese (Anser anser) and show that phenotypic variation in dominance‐related behaviours contains significant additive genetic variance, parental effects and permanent environment effects. The relative importance of these variance components varied between age and sex classes, whereby the most pronounced differences concerned nongenetic components. In particular, parental effects were larger in juveniles of both sexes than in adults. In paired adults, the partner's identity had a larger influence on male dominance rank and aggression rate than in females. In sex‐ and age‐specific estimates, heritabilities did not differ significantly between age and sex classes. Adult dominance rank was only weakly genetically correlated between the sexes, leading to considerably higher heritabilities in sex‐specific estimates than across sexes. We discuss these patterns in relation to selection acting on dominance rank and aggression in different life history stages and sexes and suggest that different adaptive optima could be a mechanism for maintaining genetic variation in dominance‐related traits in free‐living animal populations.     

Homologous and non-homologous recombination differentially affect DNA damage repair in mice

Ionizing radiation and interstrand DNA crosslinking compounds provide important treatments against cancer due to their extreme genotoxicity for proliferating cells. Both the efficacies of such treatments and the mutagenic potential of these agents are modulated by the ability of cells to repair the inflicted DNA damage. Here we demonstrate that homologous recombination-deficient mRAD54(-/-) mice are hypersensitive to ionizing radiation at the embryonic but, unexpectedly, not at the adult stage. However, at the adult stage mRAD54 deficiency dramatically aggravates the ionizing radiation sensitivity of severe combined immune deficiency (scid) mice that are impaired in DNA double-strand break repair through DNA end-joining. In contrast, regardless of developmental stage, mRAD54(-/-) mice are hypersensitive to the interstrand DNA crosslinking compound mitomycin C. These results demonstrate that the two major DNA double-strand break repair pathways in mammals have overlapping as well as specialized roles, and that the relative contribution of these pathways towards repair of ionizing radiation-induced DNA damage changes during development of the animal.     

Hybridization and regional sex ratios in Nemophila menziesii

I tested whether a region of high female frequencies in the gynodioecious plant, Nemophila menziesii, may be due to hybridization between regionally distributed populations with different corolla colours. I crossed plants in the greenhouse from populations with different corolla colours and found that hybrid crosses yielded higher frequencies of females than within-colour crosses. In the field, I found that populations with high female frequencies had intermediate mean corolla colours and higher variance in corolla colour, two traits suggesting hybridization. Nemophila menziesii has nuclear-cytoplasmic sex inheritance, thus if populations with different corolla colours are fixed for different male-sterile cytoplasms and matching nuclear restorer alleles, hybridization between populations with different corolla colour should yield high frequencies of females. Two populations that are all hermaphroditic in the field segregated females in hybrid crosses suggesting that field populations may contain sex ratio distorters but appear undistorted, a prediction of genomic conflict theory.     

EXO1 and MSH4 differentially affect crossing-over and segregation

The 5′-3′ exonuclease Exo1p from Saccharomyces cerevisiae is required for wild-type levels of meiotic crossing-over and normal meiotic chromosome segregation as is the meiosis-specific MutS homologue, Msh4p. Mutations in both genes reduce crossing-over by approximately two-fold, but Δmsh4 strains have significantly lower viability and a higher frequency of meiosis I non-disjunction. Epistasis analysis indicates a complex interaction between the two genes. Although crossing-over was not detectably lower in the double mutant, viability was significantly worse than either single mutant. Such a result suggests that the two genes are affecting meiotic viability by distinct mechanisms. We propose that Δexo1 affects chromosome segregation by reducing crossing-over, while Δmsh4 affects both the frequency and distribution of crossovers. Mutation in EXO1 reduces gene conversion frequencies significantly at some but not all loci, suggesting that other enzymes are also involved in DNA resection. We propose that Exo1p plays an early role in establishing some recombination intermediates by generating single-stranded tails. The role of Msh4p is suggested to be in determining whether some recombination intermediates are resolved as crossover events and in generating crossover interference. The synergistic effect of Δexo1Δmsh4 on spore viability suggests that the two genes have partially compensatory roles in a process affecting meiotic success. Received: 10 November 1999; in revised form: 14 January 2000 / Accepted: 14 January 2000