FREE NEWSLETTER: Does coffee really dehydrate you?

Tomorrow, the April edition of the free newsletter goes out to subscribers. It covers a study in which the researchers tested whether moderate coffee consumption does actually lead to dehydration.

This is important because caffeine is known to have a diuretic effect when consumed in high doses. And, since coffee contains caffeine, is widely assumed that drinking coffee leads to dehydration. However, some studies have reported that regular consumption of caffeine leads to resistance to its diuretic effects, which may mean that a regular caffeine habit does not lead to a reduced hydration status.

Also, since coffee contains other compounds in addition to caffeine, these may interact with one another and lead to different effects. And since few have actually investigated the effects of coffee on hydration status, this means that we don’t actually know whether moderate coffee consumption is dehydrating or not.

Amazing, really, given how much coffee is consumed every day around the world…

To get access to this free study review, please just fill in the form HERE. We promise only to send you two emails per month, one with a free study review and another with a short preview of the monthly research review service, just before it goes out.

Do heavy loads lead to bigger strength gains than light loads?

Most strength and conditioning professionals believe that training with heavier relative loads leads to improved strength gains in comparison with lighter relative loads. But how good is the evidence for this contention? Does training with heavier relative loads in fact lead to greater strength gains than training with lighter relative loads? Here is a review of the literature…

What is the background?

When developing guidance for resistance-training programs, strength and conditioning coaches and sports science researchers generally refer to three different bands of relative load, typically described as heavy (1 – 5RM), moderate (6 – 15RM) and light (15RM+, which corresponds with <65% of 1RM).

While the division between heavy and moderate relative loads is somewhat arbitrary, it is thought that the division between moderate and light loads represents a fundamental dividing line. Previous researchers and coaches have generally assumed that training with light loads of <65% of 1RM is less effective for both strength and hypertrophy gains than training with heavy loads, even in beginners.

When I reviewed the literature comparing heavy and light loads for the purposes of hypertrophy in a previous blog post, it was interesting to see the studies were not conclusive. It was not clear that heavier relative loads were any different in their ability to produce hypertrophy.

However, as we will see in this review, the evidence for heavy loads (here defined as heavier than 15RM) being superior for strength gains in comparison with lighter loads (here defined as lighter than 15RM) is actually much stronger.

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Do heavy loads lead to greater strength gains than light loads?

The following studies have assessed the differences in strength gains resulting from using heavy (1 – 5RM) vs. light (15RM+) loads in untrained populations. To my knowledge, no studies have been performed in trained populations.

Campos (2002) – the researchers recruited 32 untrained males for an 8-week resistance-training program and allocated them into a low-rep group (3 – 5RM for 4 sets of each exercise with 3 minutes of rest between sets and exercises), an intermediate-rep group (9 – 11RM for 3 sets with 2 minutes of rest), a high-rep group (20 – 28RM for 2 sets with 1 minutes rest), and a control group. The subjects performed the leg press, squat, and knee extension 2 days per week for the first 4 weeks and 3 days per week for the second 4 weeks. The researchers found significant increases in 1RM strength for all three exercises in all three training groups. These strength gains were significantly greater in the low-rep group compared to the high-rep group.

Holm (2008) – the researchers recruited 11 sedentary males for a 12-week intervention in which each subject trained 3 times per week, with one leg at 70% of 1RM (heavy load) and the other leg at 15.5% of 1RM (light load). The researchers tested 1RM knee extension, isokinetic and isometric strength For 1RM knee extension, the researchers found that the strength gain was significantly higher following the heavy load condition (36 ± 5%) than following the light load condition (19 ± 2%). Similarly, the researchers found that the heavy load condition improved concentric isokinetic strength by 13 ± 5%, eccentric isokinetic strength by 18 ± 5% and isometric strength by 15 ± 4% but the light load condition did not change any of these measures significantly.

Van Roie (2013) – the researchers compared the effects of high- and low-load resistance-training on muscle volume in 56 older adults performing an intervention of 12 weeks of leg press and leg extension training at either high (2 × 10 – 15 reps at 80% of 1RM, low (1 × 80 – 100 reps at 20% of 1RM), or low+ (1 × 60 reps at 20% of 1RM followed by 1 × 10 – 20 reps at 40% of 1RM) relative loads. The researchers reported that each of the training groups significantly increase both leg press and leg extension 1RM post-intervention. For the leg press, the high and low+ groups increased significantly more than the low group (46.2  ± 32.3% and 39.2 ± 20.7% vs. 23.1 ± 20.7%). For the knee extension, the high and low+ groups increased significantly more than the low group (30.0 ± 11.5% and 29.7 ± 19.8% vs. 19.2 ± 5.3%).

Tanimoto (2008) – the researchers recruited 36 healthy but untrained young males who performed whole-body resistance training 2 times per week for 13 weeks using 3 sets each of the squat, chest press, lat-pull-down, abdominal bend, and back extension. The subjects were allocated into 3 groups: light-slow (55 – 60% of 1RM with 3-second eccentric and concentric actions), heavy (80 – 90% of 1RM with 1-second concentric and eccentric actions and a 1-second pause) and a control. The researchers observed no significant differences between the groups in respect of 1RM strength. However, there was a non-significant trend for the light-slow group to increase to a lesser extent than the heavy group (33.0 ± 8.8% vs. 41.2 ± 7.8%). Also, the increase in 1RM strength for the back extension exercise was significantly greater in the heavy group than in the light-slow group.

Tanimoto (2006) – the researchers recruited 24 healthy but untrained young males who performed whole-body resistance training 3 times per week for 12 weeks with 3 sets of knee extension exercise. The subjects were allocated into 3 groups: light-slow (50% of 1RM with 3-second eccentric and concentric actions), light-normal (50% of 1RM with 1-second eccentric and concentric actions and a 1-second pause), and heavy (80% of 1RM with 1-second concentric and eccentric actions and a 1-second pause). The researchers measured 1RM knee extension, isometric and isokinetic strength at 90, 200 and 300 degrees/s. There were no significant differences between isokinetic or 1RM strength gains between the groups. However, the heavy-load group increased isometric strength by significantly more than the light groups.

Mitchell (2012) – the researchers recruited 18 healthy but untrained young males for a 10-week study in which they performed single-leg resistance-training 3 times per week. The researchers randomly allocated each of the subjects’ legs to 1 of 3 different training protocols that differed by volume and by relative load, as follows: 30% of 1RM x 3 sets, 80% of 1RM x 1 set, and 80% of 1RM x 3 sets. The researchers found that all training protocols led to significant increases in 1RM but the increase in 1RM was greater in the 80% of 1RM x 1 set and 80% of 1RM x 3 set conditions than in the 30% of 1RM x 3 sets condition. The researchers also reported that isometric strength increased in all conditions but there were no significant differences between conditions.

Ogasawara (2013) – the researchers recruited 9 young, untrained males for a 6-week, high-load-resistance-training program for the bench press using 75% of 1RM for 3 sets, 3 times per week, followed by a 12-month detraining period, followed by a 6-week, low-load-resistance-training program using 30% of 1RM for  4 sets, 3 times  per week. The researchers found that post-intervention, 1RM and isometric strength both increased significantly in both groups. However, they found that the increase in the heavy-load group was significantly greater than that in the light-load group for both (1RM 21.0 ± 5.9% vs. 8.6 ± 2.9%) and isometric (13.9 ± 7.5% vs. 6.5 ± 4.9%) strength measures.

Moss (1997) – the researchers recruited 30 physical education students and randomly allocated them into 1 of 3 groups, who trained with loads of either 90%, 35%, or 15% of IRM. The groups trained using 3 – 5 sets, 3 times per week for 9 weeks. The 90% group trained using 2 reps, the 35% group using 7 reps and the 15% group using 10 reps. The researchers reported that 1RM increased by 15.2 ± 4.5%, 10.1 ± 5.9% and 6.6% in each of the 90%, 35% and 15% groups, respectively. The researchers found that the increase in the 90% group was significantly greater than the increase in the 15% group.

Anderson (1982) – the researchers assessed the effects on strength gains of 3 different resistance training programs: high resistance-low repetition, medium resistance-medium repetition, and low resistance-high repetition. The researchers found that the high resistance-low repetition training condition led to significantly greater strength gains than the other two conditions.

Aagaard (1996) – the researchers compared the effects of strength training using high loads and slow speeds (4 sets of 8 reps with 8RM loading) and low loads and high speeds (4 sets of 24 reps with 24RM loading) in 22 elite soccer players. Before and after the trial, the researchers tested isokinetic concentric and eccentric knee extension and flexion torques at 30, 120, 240 degrees/s. The researchers found that isokinetic knee strength did not increase significantly in the low load group. On the other hand, concentric torque increased significantly in the high load group for both knee extension and flexion at 30 degrees/s and eccentric torque increased significantly at 30, 120 and 240 degrees/s.

Weiss (1999) – the researchers compared the effects of three resistance-training protocols with either high, moderate or low loads in 38 untrained males. The subjects trained 3 times per week for 7 weeks with 4 sets of squats using a 3 – 5RM, 13 – 15RM, or 23 – 25RM load, respectively. The researchers found that squat strength and knee extension peak torque at 60 degrees/s significantly increased in all groups. However, squat strength improved significantly more in the high-load group than in the low-load group.

Bemben (2000) – the researchers compared the effects of two volume-matched, high-load (80% of 1RM) and low-load (40% of 1RM) resistance-training protocols on strength gains in 25 early postmenopausal, estrogen-deficient women. The protocols were performed for 3 sets, 3 days per week for 6 months. The researchers found that while both training groups displayed similar increases measures of lower body strength and hip strength, the high-load group displayed significantly greater improvements in upper body strength (25% vs. 16%).

Rana (2008) – the researchers assessed the effects of relative load on strength gains in 34 healthy adult females who performed a 6-week resistance-training program comprising the leg press, back squat and knee extension. The researchers allocated the subjects into various different groups, including a control, a traditional strength (heavy) group, a traditional endurance (light) group, and a slow-velocity group. The heavy group trained at 6 – 10 RM, the light group trained at 20 – 30RM, both with 1 – 2 second concentric and eccentric phases, and the slow-velocity group trained using a 6 – 10RM with a 10-second concentric and 4-second eccentric phase. Comparing just the traditional strength and traditional endurance groups, the researchers found that the traditional strength group displayed significantly greater 1RM strength gains in the leg press and knee extension exercises than the endurance group. The traditional strength group also showed a non-significant trend to display greater increases in strength for the squat.

Popov (2006) – the researchers recruited 18 young, physically active males for an 8-week intervention, in which they trained their leg extensor muscles 3 times per week using the leg press exercise. A heavy group worked at 80% of MVC and a light group worked at 50% of MVC. The researchers reported that strength increased significantly in both the heavy and light groups. While there was a non-significant trend for the heavy group to increase strength (measured as maximum force developed during the leg press exercise) to a greater extent (35% vs. 21%), there was no significant difference between the groups.

Hisaeda (1996) – the researchers compared the effects of two resistance-training protocols using the knee extension exercise in 11 untrained female subjects. In a light-load protocol, the subjects used 4 – 5 sets of 15 – 20RM with sufficient inter-set rest periods. In a heavy-load protocol, the subjects used 8 – 9 sets of 4 – 6RM with a 90-second inter-set rest period. Before and after the intervention, the researchers measured isokinetic knee extension torque at 0, 60, 180, and 300 degrees/s. The researchers found that isokinetic torque increased significantly in both groups but there was a non-significant trend for the light-load protocol to lead to greater strength gains (43.4 ± 47.5% vs. 27.4 ± 31.3%).

Stone (1994) – the researchers compared the effects of three resistance-training protocols with either high, moderate and low loads in 50 untrained females. The protocols involved 9 weeks of training either involving 3 sets of 6 – 8RM, 2 sets of 15 – 20RM, or 1 set of 30 – 40RM, respectively. The researchers found that in all groups there were significant strength gains as measured by 1RM but there were no significant differences between groups. There was a non-significant trend for the high-load group to display the greatest gains in strength.

Leger (2006) – the researchers recruited 25 healthy but untrained males for an 8-week intervention of resistance training followed by de-training. The subjects were allocated into one of two training groups (low reps or high reps) that were matched for age, height, weight, VO2-max and muscular strength and endurance. The subjects performed the same training protocol as described in Campos (2002) above. The researchers found that resistance training led to 50% and 15% strength gains in the leg extension and squat, respectively, but there was no strength gain for the leg press exercise. The researchers found no significant differences in strength gains between the two groups and did not provide data for the two groups separately. Therefore, it was not possible to ascertain whether there was any non-significant trend.

Pruitt (1995) – the researchers compared the effects of two resistance-training protocols with either high or low loads in 26 older females (65 – 82 years). The high-load group performed 7 repetitions at 80% of 1RM and the low-load group performed 14 repetitions at 40% of 1RM) for 3 sets each in 10 exercises, 3 times per week for 1 year. The researchers found that arm strength increased significantly more in the low-load group than in the high-load group (65.5% vs. 27.4%). However, both high- and low-load groups displayed significant increases in 1RM for chest (10.1% vs. 15.4 %), shoulders (18.5% vs. 27.4 %), upper back (41.4% vs. 21.0 %), lower back (35.8% vs. 35.4 %), hips (50.9% vs. 66.4 %), and legs (47.6% vs. 42.4%) with no significant differences between these increases.

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How can we summarize the results of these studies?

The following table sets out the results of the preceding studies. It shows that in 13 out of the 18 studies presented above, there was a significantly superior strength gain in the heavier load condition in comparison with the lighter load condition. In 3 further studies, there were no significant differences between conditions albeit there was a non-significant trend in favour of a bigger strength gain in the heavier load condition in comparison with the lighter load condition. In 1 further study, there was no significant difference between conditions and no data were presented to allow the determination of non-significant trends. In 1 final study, the lighter load condition achieved greater strength gains than the higher load condition.

Heavy versus light

In conclusion, it seems clear that while training with both heavy and light loads can lead to strength gains, training with heavier loads (here defined as heavier than 15RM) leads to superior strength gains than training with lighter loads (here defined as lighter than 15RM).

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What are the practical implications?

For personal trainers

When working with untrained individuals, personal trainers can be assured that some strength gains will occur even with very light loads.

For maximizing strength gains in untrained individuals, personal trainers should be aware that using heavier loads than 15RM is optimal.

For strength athletes

For maximizing strength gains, strength athletes should make use of loads that are heavier than 15RM.

Does training more frequently lead to bigger strength gains (part two)?

The effect of training frequency on strength is difficult to assess. In the fitness industry, 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 are a number of studies but many of them do not control for the effect of increased volume. This review sets out what we currently know about how frequency affects strength gains, where volume is maintained the same.

What is the background?

Introduction

Training frequency has traditionally been considered important for strength gains. However, training frequency is often (but not always) manipulated for the purposes of indirectly altering total weekly training volume.  Indeed, in many research studies investigating frequency, total weekly training volume is often not equated between the groups. This leads to a greater total volume of training being performed by the high-frequency group. Since volume may also be a key factor, this is a confounding factor.

Therefore, it is important to consider what happens to strength gains when frequency is altered while maintaining total weekly training volume the same. This will provide information about whether splitting the same total weekly workload into more sessions would be superior to performing fewer but longer training sessions.

Selection criteria

The purpose of this short review is to assess the effects of training frequency on strength gains measured by any metric in 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 do not 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.

Meta-analyses of frequency

Meta-analyses have been performed in relation to the dose-response effect of strength training interventions, including the specific effect of frequency, by Rhea (2003) and Silva (2007). These meta-analyses investigated the dose-response effect of resistance-training (subdivided by volume, frequency and relative-load).

Rhea et al. reported that for training frequency of each muscle group, untrained individuals experience a dose-response up to 3 days per week while trained individuals experience a dose-response relationship up to 2 days per week.

Silva et al. investigated purely elderly subjects and reported that any combination of training variables led to increases in strength and only the length of time spent training had a significant dose-response relationship with strength gains.

As we will see, the findings of the meta-analysis by Rhea et al. do not entirely agree with the conclusions that we can draw from the following studies, which have directly compared lower and higher frequencies of training. This may be because the meta-analysis does not appear to control adequately for the confounding effect of volume in assessing frequency. It seems to me that what was actually assessed in that meta-analysis was the “number of training sessions” and not frequency independent of volume, which is the target of this review.

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What is the effect of frequency on strength gains in trained subjects?

The following long-term training studies have explored the effects of different volume-matched frequencies of training on strength gains in trained subjects:

McLester (2000) performed a 12-week investigation involving trained subjects divided into two groups, one of which performed resistance training 1 day per week for 3 sets of upper and lower body exercises at 80% of 1RM with 2 minutes of inter-set rest. The other group trained 3 days per week for 1 set of each exercise at 80% of 1RM. The number of sets was set in order to keep total volume constant. The researchers reported the total upper and lower body exercise percentage increases in the 1-day and 3-day groups were 20.2% vs. 32.4% (upper) and 23.5% vs. 37.4% (lower). There were no significant differences between groups, although there was obviously a strong but non-significant trend for the sum of all exercise percentage increases in both the upper and lower body to be greater in the higher frequency group. Also, there was a significant difference in respect of the leg press, which displayed a 22.3% vs. 46.1% increases in favour of the high-frequency group.

Häkkinen and Kallinen (1994) performed a 6-week cross-over investigation involving trained female subjects. The subjects performed a sequence of two 3-week periods of resistance-training for the quadriceps, training 3 times a week. In one period, the subjects trained once on each training day and in the other period they trained using an identical volume over two sessions. In the 3-week period involving training once per day, the researchers observed no changes in the maximal voluntary isometric strength of the leg extensors. However, they did note significant increases in maximal isometric strength of the leg extensors of 5.1% from 2493 ± 553 to 2620 ± 598N in the 3-week period involving training two times per day. The researchers reported that this increase was much greater than that achieved in the 3-week period involving training once per day, which was an increase of just 0.1%. However, as Carpinelli (2004) has noted, these data do not match the data in the table, which report an increase of 13.2% from 2258 ± 652 to 2555 ± 555N in the 3-week period involving training once per day. It seems likely that there is an error in the data presented in the table.

Hartmann (2007) performed a 3-week investigation into the effects of twice- and once-daily training sessions with similar training volumes in 10 nationally competitive male weightlifters on isometric knee-extension strength, vertical-jump peak power and weightlifting performance. The researchers did not observe any significant differences between the two groups. However, they did find that there was a greater non-significant percentage increase in isometric knee-extension strength (5.1% vs. 3.2%) in the twice-daily training group than in the once-daily training group. It is important to note that the duration of the study very short and the training status of the subjects very high and this might have led to a greater chance of type II error occurring.

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How can we summarize the literature?

The following chart summarizes the results of the studies described above:

Frequency - trained - controlled

In summary, there appears to be a trend towards a higher volume-matched frequency causing greater strength gains in trained subjects. However, there is very little evidence to build a case and further research is needed.

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What is the effect of frequency on strength gains in untrained subjects?

The following long-term training studies have explored the effects of different volume-matched frequencies of training on strength gains in untrained subjects:

Calder (1994) performed a 20-week investigation in 30 young women in 3 groups who performed either whole-body training, upper-lower split training or no training (a control). The whole-body group performed 4 upper (5 sets of 6 – 10RM) and 3 lower body (5 sets of 10 – 12RM) resistance exercises in single sessions twice a week. The upper-lower split group did the upper body exercises on 2 days a week and the lower body exercises on 2 other days of the week. The researchers reported that 1RM increased significantly in the arm curl, bench press and leg press exercises in both the whole-body training and upper-lower split training groups by 54% vs. 69%, 33% vs. 32%, and 21% vs. 22%. There was therefore no difference between the improvements attained by the two groups.

Benton (2011) investigated the effects of 8 weeks of 3 versus 4 days per week of volume-matched resistance-training on body composition in middle-aged women. The 3-day group completed 3 sets of 8 exercises arranged as a whole-body routine and the 4-day group completed 3 sets of 6 upper body exercises or 6 sets of 3 lower body exercises, arranged as an upper-lower split routine. Both groups of subjects performed 72 sets per week of 8 – 12 repetitions at 50 – 80% of 1RM. The researchers reported no significant differences in strength gains between the two groups. They found that chest press 1RM increased 34% in both groups while leg press 1RM increased 29% in the 3-day group and 49% in the 4-day group. There was therefore a trend for greater lower body strength gains in the higher frequency group.

Candow and Burke (2007) investigated the effects of 6 weeks of 2 versus 3 days per week of volume-matched resistance-training on strength gains in 29 untrained subjects, who performed either 3 sets of 10 repetitions to fatigue twice a week or 2 sets of 10 repetitions 3 times per week of the squat and bench press. The researchers reported that both groups significantly improved both squat and bench press strength. They found that the relative increases in squat 1RM for the 2-day and 3-day groups were similar (29% vs. 28%) while the relative increase in bench press 1RM was slightly higher in the higher frequency group (22% vs. 30%). However, there were no significant differences between groups.

Arazi and Asadi (2011) divided 39 healthy but untrained males into four groups: one group performing 1 session of total-body resistance training (12 exercises, once a week), another group performing total-body resistance training divided into 2 sessions (6 exercises, twice a week), an upper-lower split group performing 3 sessions per week (4 exercises, three times a week), and a control group (hereafter called 1-day, 2-day, 3-day and control groups). All groups performed the same volume and number of exercises, which comprised the leg press, leg curl, leg extension, calf raise, lat pull-down, lat pull-row, bench press, pec fly, arm curl, dumbbell arm curl, triceps push-down, and dumbbell triceps extension.  Before and after the intervention, the researchers estimated bench press and leg press 1RM based on the performance of an 8RM. The researchers reported that each of the 1-day, 2-day, 3-day groups significantly increased both bench press 1RM and leg press 1RM following the intervention. However, they did not observe any significant differences between any of the training groups. The researchers did not provide numerical figures for the improvements so it is difficult to assess whether there were any non-significant changes. However, based on the charts provided it does not appear that there were any frequency-related trends.

Hunter (1985) compared the effects of either 3-days or 4-days per week of training frequency in 46 untrained males and females. The subjects all performed 9 sets each of 7 exercises (bench press, squat, power clean, behind-the-neck press, biceps curl, behind-the-neck pull-down, and thigh curls) with a 7 – 10RM for a 7-week period. The researchers found that the 3-day and 4-day groups both significantly improved bench press strength (14.1% vs. 21.9 %) and there was no significant difference between the groups. However, the 4-day group did display a non-significantly greater improvement.

Andersen (2012) compared how distributing 1 hour per week of strength training for the neck and shoulder muscles would affect neck pain, disability and strength gains in 447 office workers with and without neck and/or shoulder pain. The subjects were randomly allocated into 1 of 4 strength training groups: 1 session of 60 minutes, 3 sessions of 20 minutes, or 9 sessions of 7 minutes, or to a non-training control group. The researchers assessed self-reported neck and shoulder pain, work disability, and strength improvements in the lateral raise exercise. The researchers reported that 10RM lateral raise performance increased by 0.16kg per week in the 1 x 60-minute group, which was significantly faster than the 9 x 7-minute group, which displayed an average increase of 0.07kg per week. The increase in the 3 x 20-minute group was 0.12kg per week but this was not significantly different from either of the other two training groups.

***

How can we summarize the literature?

The following chart summarizes the results of the studies displayed in the preceding section:

Frequency - untrained - controlled

In summary, there is very limited evidence for the beneficial effects of either a higher volume-matched training frequency or a lower volume-matched training frequency on strength gains for untrained individuals. The research is very conflicting and it is not possible to draw a definitive conclusion at this stage.

***

What are the practical implications?

For trained individuals

Increasing frequency may be an effective way of maximizing strength gains, even if this occurs simply by redistributing the same volume over a greater number of sessions.

For untrained individuals

Increasing frequency may not be as effective for strength gains as in trained subjects and the research is currently conflicting. Therefore, sticking to a traditional number of sessions (e.g. three times per week) may be the most conservative course of action.

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?

Introduction

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.

Selection criteria

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 was 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.

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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:

Frequency - not controlled

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.

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What are the practical implications?

For personal trainers

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.

 For strength athletes

Where athletes 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.

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