The Effects of Weight Training on 1 RM Bench Press Strength
Purpose
The purpose of this experiment was to test the effect of six weeks of weight training on
1RM bench press strength
Methods
Subjects
Thirty five subjects volunteered to participate in the study Their mean ± SD age, height
and body mass was 25.3 ± 2.7 yr, 165.8 ± 12.7 cm and 69.6 ± 3.9 kg, respectively.
Study Design
The study was an independent groups design in which subjects were randomly assigned
to the following training groups: 1 set of 10 reps 3 times per week, 2 sets of 10 reps 3 times per
week, 3 sets of 10 reps 3 times per week, 4 sets of ten reps 3 times per week, and control
group. The control group did not participate in strength training. The difference between pretraining and six week post-training 1 RM bench press strength was computed for each group.
Reproducibility of 1RM bench press measurements were computed in a separate reliability
study.
Procedures
The subjects reported to the weight room 3 times per week and completed their
assigned number of sets. Each week the weights were adjusted so that the subjects could not
complete the 10 repetition on their last set.
Measurement of Reliability
Eight subjects (not in the experiment) participated in a test-retest assessment of
measurement reliability. One repetition maximum (1RM) squat was measured on each athlete
on two different days(8). The between day reliability was determined using SPSS (ver 18) to
compute the intraclass correlation coefficient (ICC) using a two factor mixed-effects model with
type consistency. The average measures test-retest ICC for 1RM squat strength was 0.973 with
a 95% confidence interval (CI) of 0.864 – 0.995. The mean change in 1RM squat strength
between days was 2.8 ± 10.7 Kg. The sample size adjusted or unbiased standard error of
measurement(4) was 7.83 Kg [95% CI 5.17 – 15.93 Kg]. The minimum detectable change
(MDC), which is considered the minimal amount of change that is not likely to be due to chance
variation in measurement was computed using the following formula:
𝑀𝐷𝐶95% = 1.96 × √2 × 𝑆𝐸𝑀
𝑀𝐷𝐶95% = 1.96 × √2 × 7.83
𝑀𝐷𝐶95% = 21.70 𝐾𝑔
where MDC95% is the minimum detectable change at the 95% confidence level, and the SEM is
the unbiased estimate of the standard error of measurement. Therefore, the MDC 95% in 1RM
squat strength was 21.70 Kg.
A Priori Statistical Power Analysis
G*Power Version 3.0 was used to determine sample size using a meaningful significant
difference in 1RM squat strength of 43.40 Kg (2 × MDC95), an SD of 32.85 Kg [this is the average
sd of the day 1 and day 2 measures], a 2-tailed t- test and an alpha level of 0.05. To obtain an
estimated power of 80%, 7 subjects per group would be required.
Statistical Analysis
The change (post-pre) in 1 RM bench press strength was computed for each group.
Data were analyzed using SPSS version 18.0 for Windows. Values are expressed as means ± SD.
The distribution of each variable was examined with the Kolomogorov-Smirnov and ShapiroWilk normality tests. A single factor ANOVA was performed to detect significant differences in
the change in 1 RM bench press strength by levels of training group (1 set, 2 sets, 3 sets, 4 sets,
control). Training group was a between subjects factor. Follow-up tests of significant ANOVA
effects were compared using the Tukey post hoc test. The level of significance was set at P <
0.05.
Results
The means ± SDs for change in 1 RM bench press strength by training group (1 set, 2
sets, 3 sets, 4 sets, control) are shown in Figure 1.
10
Change in Strength (Kg)
9
8
7
6
*
*
5
*
4
3
2
1
0
1 Set
2 Sets
3 Sets
(* indicates significantly different from group 2, p < 0.05)
4 Sets
Control
The K-S and S-W tests of normality indicated that the variables were normally distributed.
Levene’s test of homogeneity of variance indicated that the groups had equal variance. There
was a significant difference between training groups [F(4,34) = 8.024, p = 0.000]. As shown in
Figure 1, doing 2 sets per session (7.86 ± 1.67 Kg) was significantly different from: 1 set (5.29 ±
1.11 Kg), 3 sets (5.0 ± 0.87 Kg) and control (4.43 ± 0.98 Kg). No other pairwise comparisons
were significant.
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