Does training more frequently lead to bigger strength gains?
The effect of training frequency on strength is difficult to assess. There are strong proponents of both infrequent (once per week) and very frequent (6+ times per week) training approaches, both on a body-part and on a full-body basis. In the literature, there many relevant studies. Some of them control for the effect of increased volume while others do not. This review sets out what we currently know about how frequency affects strength gains, where volume is NOT maintained the same, since this is the way that most people use frequency as a variable (i.e. to increase volume).
What is the background?
Training frequency is often considered important for strength gains. However, training frequency is sometimes increased for the purposes of spreading the same training load over a larger number of weekly sessions and sometimes for indirectly increasing total weekly training volume. Therefore, it is important to consider what happens in both scenarios (maintaining weekly volume constant and allowing weekly volume to increase). This review considers the latter scenario.
The purpose of this short review is to assess the effects of training frequency on strength gains measured by any metric in non-volume-matched studies of resistance-training-only interventions in both trained and untrained populations, where training frequency is >1 session per week. This involves the following selection criteria:
Including any intervention assessing the effects of training frequency on strength gains.
Measurement of strength gains by any metric (e.g. dynamic/isoinertial, isometric or isokinetic).
Excluding interventions that control for total weekly training volume.
Excluding interventions with aerobic exercise or other components that are not resistance-training.
Excluding interventions where resistance-training was performed for <1 session per week.
What is the effect of frequency on strength gains?
The following long-term training studies have explored the effects of different frequencies of training (not volume-matched) on strength gains in untrained or lightly-trained subjects:
Gillam (1981) – the researchers assessed the effects of training frequency in 68 male subjects divided into 5 groups. In each of these groups, the subjects performed 18 sets of 1RM of the free-weight bench-press exercise either once, twice, 3 times, 4 times or 5 times for a 9-week training intervention. The researchers found that the groups training 3, 4 and 5 times per week displayed significantly greater strength gains (32.3%, 29.0 % and 40.7%) than the group training once per week (19.5%).
Braith (1989) – the researchers compared the strength gains resulting from resistance-training either 2 or 3 days per week for either 10 or 18 weeks in 117 untrained subjects. The subjects were randomly allocated to various training groups. Each group trained using 1 set of 7 – 10 repetitions of bilateral knee extensions with variable resistance. The researchers found that all groups significantly increased isometric strength. However, they also found that the 3-days per week groups increased isometric strength (10 weeks = 21.2% and 18 weeks = 28.4%) more than the 2-days per week groups (10 weeks = 13.5% and 18 weeks = 20.9%).
Pollock (1993) – the researchers assessed the effect of frequency on strength gains following machine-based cervical extension resistance-training in 50 male and 28 female subjects over a 12-week intervention. The subjects were allocated to groups that trained either once or twice per week and also to groups that trained using either purely dynamic exercise or both dynamic and isometric exercise, creating four groups: once-dynamic, once-dynamic + isometric, twice-dynamic, and twice-dynamic + isometric. The researchers found that all training groups improved cervical extension strength significantly at all 8 isometric angles tested except for the dynamic group training once per week, which did not improve at 0 degrees of cervical flexion. The researchers observed a greater increase in strength in the groups training twice per week compared to those training once per week, with the greatest increases in isometric torque in each of the once-dynamic, once-dynamic + isometric, twice-dynamic, and twice-dynamic + isometric groups being 21.9%, 22.4%, 10.0% and 15.1%, respectively. However, increases in dynamic strength were not significantly different between groups in respect of frequency.
DeMichele (1997) – the researchers assessed the effect of frequency on torso rotation muscle strength in 33 males and 25 females after 12 weeks of training. The subjects trained either 1, 2 or 3 times per week. Each group trained both left and right rotations for 8 – 12 repetitions of full range dynamic variable resistance exercise to failure. The researchers measured increases in isometric torso rotation torque at different angles (54 degrees, 36 degrees, 18 degrees, 0 degree, -18 degrees, -36 degrees, and -54 degrees). The researchers reported that the average increases across all angles in each of the groups training 1, 2 and 3 times per week were 4.9%, 16.3%, and 11.9%. The groups training 2 and 3 times per week increased strength significantly with respect to a non-training control while the group training 1 times per week did not. Dynamic training load increased significantly more in the groups training 2 and 3 times per week than in the group that trained 1 time per week.
Farinatti (2013) – the researchers assessed the effect of training frequency on strength gains in 48 elderly women aged >60 years over a 16-week training program. The subjects performed 1 set of 10RM for several exercises either 1, 2, or 3 days per week. The exercises comprised the bench press, seated dumbbell curl, knee extension and standing calf raise. The researchers found that all groups increased 10RM strength in all exercise. However, they found that for the seated dumbbell curl and knee extension was greater in the higher frequencies.
DiFrancisco-Donoghue (2007) – the researchers assessed the effects of training frequency in 18 elderly subjects aged 65 – 79 years. The subjects were randomly assigned to 1 or 2 groups who trained either 1 or 2 times per week. Both groups performed 1 set of 6 exercises at 75% of 1RM with 10 – 15 repetitions to failure for 9 weeks. The exercises comprised the leg press, leg extension, leg curl, chest fly, arm curl and seated dip. The researchers observed no difference in strength gains between the two groups. However, there was a non-significant trend for the group training 2 times per week to increase strength by more on average across the 6 exercises than the group training 1 time per week (40.0% vs. 30.8%).
Kim (2010) – the researchers assessed the effects of frequency of lumbar extension exercise on strength gains after 12 weeks in 40 patients undergoing lumbar discectomy surgery. The subjects trained 1 or 2 times per week or once every 2 weeks. The researchers found that groups training 1 and 2 times per week increased strength by 11.8% and 3.3% while the group training once every 2 weeks displayed a 8.2% reduction in strength. Despite the large numerical differences between groups, they were not significant.
Carroll (1998) – the researchers assessed the effects of frequency on strength gains following leg extensor and flexor resistance-training in 17 relatively untrained students. The subjects performed 4 upper-body and 3 lower-body exercises for 3 sets of 4 – 6 RM to 15 – 20RM, depending on the exercise, training either 2 or 3 times per week for 6 weeks. The researchers found that increases in 1RM strength were not significantly different in the groups that trained 2 and 3 times per week, although there was a non-significant trend in favor of the group training 3 times per week (32% vs. 22%). However, increases in isokinetic and isometric strength were significantly greater in the group that trained 2 times per week than the group that trained 3 times per week (22 – 50% vs. -5 – 9%). Thus, there were benefits to different strength measures from each type of training frequency and the table below therefore classifies the result as “no difference” between training groups.
Graves (1988) – the researchers assessed the effects of reducing frequency during variable resistance-training in 50 lightly-trained subjects (24 males and 26 females) following 10-week (23 subjects) and 18-week (27 subjects) phases of training. In this reduced phase, the subjects performed 1 set of 7 – 10 bilateral knee extension exercise to failure, either 1 day or 2 days per week. Prior to this phase, one group of the subjects had trained either 2 or 3 days per week. The subjects who had trained 2 days reduced their training to 1 day per week and the subjects who had trained 3 days reduced their training to 2 days per week. In the initial training phase, the researchers found that the group training 3 times per week increased isometric strength to a significantly greater extent than those who only trained 2 times per week (26% vs. 17%). There was no significant effect of training frequency in the detraining period.
Graves (1990) – the researchers assessed the effects of frequency of isolated lumbar extension resistance-training in 72 males and 42 females following a 12-weeks resistance-training intervention. The subjects were allocated to training every other week, once per week, twice per week or 3 times per week. The researchers reported that all training groups improved isometric lumbar extension torque significantly with no differences between groups. In respect of the groups training once per week, twice per week or 3 times per week, dynamic strength increased by 38.9%, 41.4% and 37.2%, respectively, but these improvements were not significantly different from one another.
Taafe (1989) – the researchers performed a randomized controlled trial to compare the effects of resistance-training 1, 2 or 3 times per week for 24 weeks in 46 elderly people aged 65 – 79 years. The training intervention comprised 3 sets of 8 repetitions at 80% of 1RM for 8 exercises for the upper and lower body. The researchers reported that strength increased significantly in each training group in all of the 8 exercises. However, there was no significant difference between groups. The average increase in strength across the 8 exercises in the groups training 1, 2 and 3 times per week was 37.0 ± 15.2%, 41.9 ± 18.2% and 39.7 ± 9.8%.
Carpenter (2001) – the researchers assessed the effect of frequency on the development of isometric lumbar extension torque over 12- and 20-week training periods in 56 subjects. The subjects trained either once every other week, or 1, 2 or 3 times per week. The training comprised 1 set of 8 – 12 repetitions of a variable-resistance lumbar extension exercise to failure. Before and after the intervention, he researchers measured isolated isometric lumbar extension torque at 7 different angles. The researchers reported that all training groups significantly increased lumbar extension torque at both 12 and 20 weeks with no significant differences between groups training >1 time per week. Moreover, there was no trend of increasing or decreasing strength gains with frequency.
Berger (1965) – the researchers assessed the effects of training frequency in 79 male subjects divided into 6 groups. In 3 of these groups, the subjects trained 2 times per week with 66%, 80%, or 90% of 1RM in addition to a weekly 1RM effort. A fourth group trained 3 times per week with the 1RM, a fifth group trained 3 times per week with 66% of the 1RM and a sixth group with the 1RM once per week. The researchers found that the group training with 66% of 1RM three times per week displayed a smaller increase in strength than the other groups. Therefore, training with 1RM once per week was as effective as training with the 1RM three times per week.
Rozier and Schafer (1981) – the researchers assessed the effects of frequency of isokinetic unilateral knee extension exercise in 23 young, female subjects over a 6-week intervention. One group trained with 3 sets of 8 repetitions daily for 5 times per week while the other performed the same protocol 3 times per week. The researchers found that both groups increased isometric and isokinetic strength gains significantly but there were no significant differences between the two groups. Moreover, the trends were for a greater increase in isometric (17% vs. 12%) and isokinetic (15% vs. 12%) strength for the lower frequency group over the higher frequency group.
How can we summarize the literature?
The following table displays the results of the studies detailed above, showing which studies found significant differences between training frequency groups and which did not, as well as those that found non-significant trends:
From the chart, we can see that the literature is somewhat conflicting. However, on balance, there seems to be evidence that a higher training frequency might well lead to bigger strength gains than a lower training frequency. On the other hand, there is much less evidence that higher training frequency will lead to inferior results. Thus, where athletes have the ability to recover from additional sessions and are motivated to perform them, it seems unlikely that this will lead to diminished strength gains.
What are the practical implications?
Personal trainers can expect to see significant strength gains with their clients training just once or twice per week. Additional sessions may lead to slightly better gains in strength.
Where individuals have the ability to recover from additional strength training sessions and are motivated to perform them, a higher training frequency may well lead to greater strength gains and it seems unlikely to lead to inferior strength gains.