This is a question post.
I've been weightlifting for a while, and I've heard vaguely good things about it's effect on productivity, like a general increase in energy levels. A recent quick google search session came up empty. If someone looks into the literature and finds something interesting I'll pay a $50 prize.*
Assume the time horizon is <5 years. I'd prefer answers focus predominantly on productivity benefits. Effects on cardiovascular could be part of an analysis, but would not qualify on their own. If the evidence is for something clearly linked to productivity, like sleep, I'd count that. Introspective evidence will also not qualify. Comparisons to other forms of exercise would be especially interesting. Assume a healthy individual, although I'm at least somewhat interested in effects on individuals with depression or anxiety given their prevalence.
*Prize to go to best answer, as judged by me, if there are any that meet some minimal threshold of rigor, also as judged by me.
answer by hereisonehand
· score: 72 (21 votes) · LW
I split my findings into categories and bolded the parts of the studies I found most interesting. I really didn't take the time to be super critical on study design, etc; I was just taking their findings at face value and seeing what, if the study was true as reported, was being claimed. Enjoy!
- Claim: “Chronic resistance exercise improves all aspects of sleep, with the greatest benefit for sleep quality. These benefits of isolated resistance exercise are attenuated when resistance exercise is combined with aerobic exercise and compared to aerobic exercise alone”
- “Improvements in sleep quality were observed across all intensities, however, effect sizes for all sleep quality outcomes (significant and non-significant) tend to be larger in studies of high intensity exercise”
- The least benefit was sleep duration
- Sleep quality was ‘perceived sleep quality’ - measured by subjective ratings
- Chronic here means avg. Of 14 weeks with an average of 60 min per session
- “There is limited evidence that combined exercise is better than aerobic exercise alone, and further study is warranted. Data from this review and recent reviews of aerobic exercise [44, 57] suggest that both modalities are effective for improving sleep quality “
2. Cognitive Function
- The impact of behavioral interventions on cognitive function in healthy older adults: A systematic review
- “Numerous experimental studies have demonstrated that exercise interventions improve cognitive abilities (Kelly et al., 2014b), but benefits have been more consistent for aerobic training, or combined cardiovascular fitness and resistance training”
- “Aerobic training (n= 13) most consistently transferred to executive function, while strength/resistance training (n = 8) most consistently transferred to cognitive inhibition and visual working memory. Similarly, aerobic/resistance combination training (n = 6) showed most consistent improvements in visual working memory”
- Acute Effects of Resistance Exercise on Cognitive Function in Healthy Adults: A Systematic Review with Multilevel Meta-Analysis.
- “Compared to NEX, RE had a positive effect on global cognition (SMD: 0.56, 95% CI 0.22–0.90, p = 0.004), but was not superior to AE (SMD: − 0.10, 95% CI 0.01 to − 0.20, p = 0.06)”
- NEX = no exercise; AE = aerobic exercise, RE = resistance exercise
- “Regarding cognitive sub-domains, RE, compared to NEX, improved inhibitory control (SMD: 0.73, 95% CI 0.21–1.26, p = 0.01) and cognitive flexibility (SMD: 0.36, 95% CI 0.17–0.55, p = 0.004)”
- Note — the reference to cognitive inhibition was referred to by the study above as well. Kind of interesting.
- “Our review detected no difference between RE and AE in acute effects on brain function. This result is in line with the meta-analysis of Northey et al. , who investigated the effects of chronic exercise on cognition in adults aged 50 years and older.”
- Lifting cognition: a meta-analysis of effects of resistance exercise on cognition
- Positive effects on composite cognitive scores, screening measures of cognitive impairments, and executive functions. no effect on measures of working memory.
- “High heterogeneity was observed in all analyses” and the authors weren’t sure why
- Long-Term Effects of Resistance Exercise Training on Cognition and Brain Volume in Older Women: Results from a Randomized Controlled Trial.
- Aerobic exercise training has been shown to attenuate cognitive decline and reduce brain atrophy with advancing age. The extent to which resistance exercise training improves cognition and prevents brain atrophy is less known, and few studies include long-term follow-up cognitive and neuroimaging assessments. We report data from a randomized controlled trial of 155 older women, who engaged in 52 weeks of resistance training (either once- or twice-weekly) or balance-and-toning (twice-weekly). Executive functioning and memory were assessed at baseline, 1-year follow-up (i.e., immediately post-intervention), and 2-year follow-up. A subset underwent structural magnetic resonance imaging scans at those time points. At 2-year follow-up, both frequencies of resistance training promoted executive function compared to balance-and-toning (standardized difference [d]=.31-.48). Additionally, twice-weekly resistance training promoted memory (d=.45), reduced cortical white matter atrophy (d=.45), and increased peak muscle power (d=.27) at 2-year follow-up relative to balance-and-toning. These effects were independent of one another. These findings suggest resistance training may have a long-term impact on cognition and white matter volume in older women.
- Exercise to reduce work-related fatigue among employees: a randomized controlled trial
- Note: This is evidence relating to aerobic, not resistance, exercise.
- “Analyses of covariance (ANCOVA) revealed that, at T1, the EI group reported lower emotional exhaustion and overall fatigue than the WLC group, however, only according to PP analyses. Both according to ITT and PP analyses, EI participants showed higher sleep quality, work ability, and self-reported cognitive functioning at T1 compared to WLC participants. Intervention effects were maintained at T2 and T3.”
- “The exercise intervention consisted of 1-hour low- intensity running sessions three times a week for a period of six consecutive weeks.”
- Exercise, inflammation, and fatigue in cancer survivors
- Effects of Different Exercise Modalities on Fatigue in Prostate Cancer Patients Undergoing Androgen Deprivation Therapy: A Year-long Randomised Controlled Trial.
- “Different exercise modes have comparable effects on reducing fatigue and enhancing vitality during ADT. Patients with the highest levels of fatigue and lowest vitality had the greatest benefits.”
4. Stuff I didn’t understand but maybe someone else does
- The effects of physical activity and exercise on brain-derived neurotrophic factor in healthy humans: A review
- “Evidence from experimental studies suggested that peripheral BDNF concentrations were elevated by acute and chronic aerobic exercise. The majority of the studies suggested that strength training had no influence on peripheral BDNF. The results from most observational studies suggested an inverse relationship between the peripheral BDNF level and habitual physical activity or cardiorespiratory fitness. “
- I just included this because I have vague memories of BDNF being related to the psychological effect of exercise, but I'm not well informed enough on this to know the implications.
- There does seem to be some effect of resistance training on cognition. These studies separated cognition into a number of subfields (executive function, visual working memory, etc).
- Every time I saw a mention of a study that did a controlled comparison of resistance training+aerobic exercise to resistance training alone, the study concluded that these were similar. It really gave me the sense that when it comes to cognitive benefits and fatigue, high intensity aerobic exercise provides the benefit, and resistance training, if it includes high intensity aerobic exercise, can capture that benefit.
- The one cognitive effect that was captured by resistance training but not aerobic exercise was cognitive inhibition, which another study also mentioned. I didn't have time to check how robust a result that was.
One final comment - while I couldn't really make a strong case for resistance training being obviously better than aerobic training with respect to productivity in any manner, I still think that 1) resistance training probably does have absolute benefits to cognition and energy levels, and 2) there are many reasons to pursue resistance training outside of productivity (for instance, things like osteoporosis risk didn't come up in a productivity-related search, but would be relevant when I design my own workout plan).
comment by Raemon
· score: 16 (8 votes) · LW
I've decided to curate this answer. (This is a bit of a nonstandard use of LW Curation. Hopefully some day we'll have a better process for curating answers)
I have similar thoughts on this answer as I do on a previous curation notice for another literature review [LW · GW]. I want LessWrong to be a place that incentives many kinds of intellectual work. Eventually, some day, I want LessWrong to be a place you can come to get the best answer given the current evidence on scientific questions, even if the data is murky.
There are a lot of pieces of that. Lit reviews are one of those pieces, and I don't think they're sufficiently incentivized by the default crowdsourced karma system.
I appreciated that this post outlined a number of concrete facts about what hereisonehand was able to find out. I also appreciated them writing up their process afterwards, so I have a sense of how reliable and representative the information is.
An area this answer could have been improved in was better distillation/presentation. (Something I considered before curating it was asking the author to optimize it a bit for readability. I ended up not doing that for slightly complex reasons but might do so in future similar situations)
Ideally, I'd hope hereisonehand's answer be followed by other people delving in more – either taking their own stab at doing a review of the literature (to sanity check whether hereisonehand's take is representative), or following up on the actual studies to get a clearer sense:
- How reliable they are
- What the causal mechanisms are
- What other fields might be relevant
- What further research might be valuable to get a more confident answer.
Longterm, I'm not sure whether this is sort of post or answer that we'd curate regularly. But right now we have relatively few levers to incentives things, and until we've built better or more flexible ones, it seemed good to reward people for important steps in the right direction (in the vein Sarah Constantin described in Tales of Alice Almost [LW · GW])
comment by jimrandomh
· score: 12 (7 votes) · LW
I think this answer was good, but also feel like curating it (and skipping the team-discussion that usually goes with curation) was a mistake. This answer really needed, at a minimum, a formatting cleanup, before it was ready for curation. I tried to read it, and I just... can't. Too many fonts, too much inconsistent indentation. And I would've appreciated a chance to make the curation email work right (ie, make it include the actual answer), before this went out.
comment by Raemon
· score: 10 (5 votes) · LW
(Quick note about the process: I discussed this with habryka and Ruby before submitting. We had considered implementing some new features to make the curation of a comment smoother, but the ideas all seemed like they'd require some time and planning to get right.
I do think it's good for Jim to voice his disagreement – the current sort-of-de-facto-norms around curating is that if at least a few people are excited about a post they can curate it and don't need to get consensus from everyone, but alway speaking from their own opinions [LW · GW] rather than speaking for the team as a whole, and it's good for the disagreement to be visible)
comment by Alexis Carlier (alexis-carlier)
· score: 14 (5 votes) · LW
Thanks for writing this! It was useful when organising my workout routine.
I read the Kovacevic et al paper on sleep you cite, and there are some caveats probably relevant to some LW readers. In particular, the benefits are less clear for younger adults.
- Acute resistance exercise studies
- "There was some evidence that an acute bout of resistance exercise may reduce the number of arousals during sleep"
- They base this on three studies. The cohorts are elderly (65-80 years), middle-aged (mean 44.4 +- 8 years), and young (21.9 +- 2.7 years). They note that "in the final study in healthy young-to-middle aged adults, no effects were observed on sleep quality measured using accelerometry, or on 5- and 7-point Likert scales following an acute bout of resistance exercise"
- Chronic resistance exercise studies
- "Overall, the data suggest that chronic resistance exercise has significant benefit on subjective sleep quality"
- They base this on seven studies. "All four studies performed in older adults reported significant improvements in sleep quality...however, results were inconsistent for younger adults, with only one out of three studies reporting significant improvements." (the study with the significant improvements was of young women).
The above results focus on sleep quality, because as you say, sleep quantity tends not to be much influenced resistance training. Nevertheless, note the following:
"The remaining study in younger adults (many with insomnia) reported a large but non- significant negative effect on sleep duration following moderate-intensity resistance training on both weekdays and weekends."
I was curious to see if this apparent age effect exists for aerobic exercise. The Kovacevic et al cite the following Kredlow et al paper as a "recent review of aerobic exercise" https://www.ncbi.nlm.nih.gov/pubmed/25596964. Indeed it seems to be predominantly about aerobic exercise, but also covers some anaerobic exercise studies. According to Kovacevic et al has 10 fewer papers on resistance training than their paper, which by my count makes it 11 resistance training papers. Kredlow et al write:
"For the majority of outcomes, there is no difference for the benefits of exercise on sleep depending on age or sex. We did, however, find significant differences for certain sleep variables. Specifically, the benefits of acute exercise did not vary by age...the benefits of regular exercise did not vary by sex and for one variable (sleep onset latency), appeared to be stronger for younger than older individuals."
Overall, it's quite unclear to me whether resistance exercise has sleep benefits for younger adults, and the evidence for aerobic exercise seems stronger (although I'd like to find a review solely of aerobic exercise studies).
comment by jp
· score: 11 (6 votes) · LW
This comment wins. This is beyond what I was hoping I would get and I'm really glad I asked. Thanks hereisonehand! Message me with paypayl/venmo/etc info to claim your prize.
comment by SoerenMind
· score: 5 (3 votes) · LW
"high intensity aerobic exercise provides the benefit, and resistance training, if it includes high intensity aerobic exercise, can capture that benefit."
Which part made you conclude that high intensity aerobic exercise is needed? Asking because most resistance training doesn't include it.
Great answer, thanks!
comment by hereisonehand
· score: 15 (4 votes) · LW
Hey! Great question. The conclusion regarding aerobic exercise came from lots of the literature I was reading saying something like "the effect went away when compared to aerobic exercise." I should probably not have said "high intensity," as I don't really remember looking specifically at any intensities, but umm - below I'll list the evidence from my answer that kind of points this out. [all of this is just pulled from my big answer comment so if you want more context, look there for the link, etc]
Having looked at it again to list the evidence, I think the evidence I saw was basically.
A. Comparison: resistance to aerobic = no difference
B. Comparison: aerobic to resistance+aerobic = no difference
So I concluded that
The effect of resistance and aerobic on sleep and cognition don't seem to be independent (or rather, at the very least they are not additive - comparison B).
I guess my thought was that if resistance = aerobic = resistance + aerobic, then either you're getting the benefits of resistance training from aerobic exercise or you're getting the benefits of aerobic exercise from resistance training. The latter just seemed more plausible to me. But I highlighted the specific sentences that led me to this below, so please just see for yourself!
"These benefits of isolated resistance exercise are attenuated when resistance exercise is combined with aerobic exercise and compared to aerobic exercise alone"
"There is limited evidence that combined exercise is better than aerobic exercise alone, and further study is warranted. Data from this review and recent reviews of aerobic exercise [44, 57] suggest that both modalities are effective for improving sleep quality"
first study: “Numerous experimental studies have demonstrated that exercise interventions improve cognitive abilities (Kelly et al., 2014b), but benefits have been more consistent for aerobic training, or combined cardiovascular fitness and resistance training”
and the 2nd study: "“Our review detected no difference between RE and AE in acute effects on brain function."
comment by ryan_b
· score: 5 (2 votes) · LW
This isn't delving deeper into the studies raised in the comment, I just wanted to emphasize the virtuous-cycle nature of a couple of these things. I got most of this from Stronger By Science, but I'll include the links to the papers directly, and the post analyzing them secondly.
Related: Meditations on Momentum [LW · GW]
First, sleep. The study linked in the answer claims resistance training improves subjective sleep quality, but the relationship works the other way as well:
Insufficient sleep undermines dietary efforts to reduce adiposity
This study found two groups on the same diet while sedentary lost the same amount of weight, but for the group on 5.5 hrs of sleep 50% of that weight loss was muscle, whereas for a group on 8.5 hrs of sleep only 20% was. This has significant implications for trying to increase or even maintain strength. More commentary here.
Sleep and muscle recovery: endocrinological and molecular basis for a new and promising hypothesis.
This review found that lack of sleep interferes with hormone balance, namely by doing things like increasing cortisol and decreasing testosterone and growth hormone. More commentary here.
In a nutshell, resistance exercise improves sleep improves resistance exercise, and so on.
Second, comparison with aerobic exercise. A couple of the studies above compared aerobic exercise with anaerobic exercise, and found the effect of one or the other was stronger (on cognitive function, for example).
As it happens, these two are also mutually reinforcing:
Resistance Training to Momentary Muscular Failure Improves Cardiovascular Fitness in Humans: A Review of Acute Physiological Responses and Chronic Physiological Adaptations
concludes that resistance training improves cardiovascular fitness; improved cardiovascular fitness results in better recovery and the ability to sustain higher resistance training loads. This effect is mitigated by specific exercises, though:
Concurrent training: a meta-analysis examining interference of aerobic and resistance exercises.
found that running interferes with strength gains, but cycling doesn't, for example. More commentary on these points here.
In a second nutshell, strength improves cardio improves strength, and so on.
So while there is independent evidence of resistance training, and aerobic training, and sleep all providing benefits relevant to productivity, they also form a mutually reinforcing system where each seems to help the other two directly.
I don't have any information on how these things scale; for example it feels ridiculous to think twice as much resistance training leads to twice as good sleep. I also don't have any indication of how much substitution there might be - for example, is the sleep benefit just because you are active at all? Is there difference between 5/week of weights vs. 5/week of cycling vs. 5/week alternating? What about if they were 30 minute workouts vs. 60 minute workouts?
That being said my gut feeling is that a combined system would be much more resilient in its benefits. Anecdotally, weights 3x a week and HIIT or yoga or something for the other 4x a week has yielded improved sleep, more stable energy throughout the day, and ~40lbs weight loss in tandem with calorie control over 7 months. This has considerably improved my productivity; I gained a couple of hours of useful time outside of work, and all the hours are higher quality now.
comment by jp
· score: 3 (2 votes) · LW
Really nice job. I think I'm persuaded by your conclusions, and I intend to try to mix in more aerobic exercise. How did you do the search?
comment by hereisonehand
· score: 16 (5 votes) · LW
Thanks! To be honest I wasn't nearly as systematic as I would've liked. I did keyword searches on Google Scholar and PubMed for resistance training and weight training. On PubMed, I specifically looked for review articles and meta-analysis in one search just to look for big picture studies, but as you can see, results were a bit sparse so I also just searched generally for any articles I could find.
I'm trying to get better at this process (ask a question, research the answer), and I'm in the early phases. Future goals include 1) having a more systematic search process to avoid bias (i guess in theory the results above could be heavily biased if I just didn't know to use certain search terms), 2) getting into the nitty gritty and actually critiquing studies and meta-analysis themselves (I just trusted blindly here, which is fine for now but it would be cool to get better at parsing methods)
answer by Raemon
· score: 6 (3 votes) · LW
List of papers
Some incremental progress, just taking the obvious first action of "search google scholar for 'benefits of exercise on productivity'", followed by a search for "benefits of strength training on productivity" after remembering that the first one wasn't quite right (but maybe still useful enough to include)
Including random quotes that seemed most relevant (did not search anything very hard)
Does strength training programme improve work task performance in young adults with Down Syndrome?
The effect of the PRT programme on work task performance will be assessed using two tests (a) repetitive weighted box stacking and (b) weight carry test (pail carry). The repetitive weighted box stacking test requires the participants to repetitively lift 10 kg boxes, from the floor to a table 75 cm off the ground. The number of boxes stacked in one minute is measured. The weighted pail carry requires participants to carry two 20 litre buckets each weighing 10 kg around an oblong 10 m course marked with cones. The total distance covered in 30 seconds is measured in metres. Running is not permitted for safety reasons. These measures are recommended by the American College of Sports Medicine  and have demonstrated changes in people with intellectual disability [34, 35].
The impact of a self-paced exercise program on productivity and health outcomes of 32 adult workers in a large federal office complex was investigated during 3 months.
Walking was the sole form of exercise. The first month, during which no walking occurred, was the control period. The second and third months were the experimental period. Participants were divided into three levels based on initial weight and self-determined walking distance goals. Productivity (using the Endicott Work Productivity Scale), walking distance (using a pedometer), and health outcomes (blood pressure, weight, pulse rate, and body fat percentage) were measured weekly. Results from this study, based on a paired t test analysis, suggest that although the self-paced exercise program had no impact on productivity, it lowered blood pressure and promoted weight loss. Further study using a larger sample and a controlled experimental design is recommended to provide conclusive evidence.
Exercise is more than medicine: The working age population's well-being and productivity
In Denmark 15 randomized controlled trials have been conducted, introducing exercise at the workplace enrolling >3500 workers. The interventions lasted from 10 to 52 weeks and offered ~1 h weekly supervised exercise during working hoursaccording to the concept of intelligent physical exercise training (IPET) that is based on evidenced sports sciences training principles and tailored to work exposure, employee health status, and physical capacity. Questionnaire surveys and health checks including blood and muscle sampling were performed at baseline and follow-up. The job groups included: office and computer workers, dentists, industrial technicians, cleaning personnel, health care workers, construction workers, and fighter/helicopter pilots.
Poor health among employees implies substantial costs for the companies. The costs relate to increased sickness presenteeism (decreased on-the-job-performance while being at the workplace) as well as absenteeism (habitual absence from work) leading to loss of work productivity.37 Sickness presenteeism was assessed as self-reported on-the-job-performance, using questions in regard to productivity, work ability, and quantity and quality of work.
Importantly, in spite of spending 1 h a week performing physical exercise training during work time, in none of our studies we found a decrease in the variables underlying on-the-job-performance.
However, we did, in an intention-to-treat analysis, find a significant 8% increase in productivity of the intervention among health care workers after 3 months but not after 1 year of intervention.38 Likewise among dentists we found improved self-reported quality of work.18
Interestingly, some exploratory analysis of our RCTs actually revealed some relevant findings: productivity increased with decreased neck/shoulder pain, and with improved muscle strength—in particular trunkflexion and extension—as well as decreased BMI among health care workers.37Further, workers with sedentary monotonous tasks (office/computer) —who were physically active at leisure compared with those being inactive—perceived less stress and more energy. These perceived differences were underlined by corresponding differences in physiological measures of the stress-hormonecortisol.39 Regarding sickness absenteeism analysis on our RCTs so far has not identified significant changes with the interventions.
The Benefits of Exercise for the Clinically Depressed
While most studies have employed walking or jogging programs of varying lengths, the efficacy of nonaerobic exercise has also been assessed. For example, in comparison with a control condition, resistance-training programs reduced symptoms of depression (resistance training vs. control resulted in BDI reduction of 11.5 vs. 4.6, respectively, p < .01, and HAM-D reduction of 7.0 vs. 2.5, respectively, p < .01).21
Aerobic and nonaerobic modes of exercise have also been compared to determine if certain types of activities are more effective than others. Doyne and colleagues22 compared the efficacy of running with that of weight lifting. Forty depressed women served as participants and were randomly assigned to running, weight lifting, or a wait-list control group. Participants were asked to complete 4 training sessions each week for the 8 weeks of the program. Depression was assessed at mid- and post-treatment and at 1, 7, and 12 months follow-up. Results indicated that the 2 activities were not significantly different, and that both types of exercise were sufficient to reduce symptoms of depression (running vs. weights vs. control resulted in BDI reduction of 11.1 vs. 13.6 vs. 0.8, respectively, p < .01, and HAM-D reduction of 6.7 vs. 8.7 vs. a 1.0 increase, respectively, p < .01).
Further, there were no differences between the 2 treatment groups during follow-up with respect to the percentage of participants who remained nondepressed. Similarly, a study by Martinsen et al.23 assessed 90 depressed in-patients who were randomly assigned to aerobic or non-aerobic exercise. Aerobic exercise consisted of jogging or brisk walking, and nonaerobic exercise included strength training, relaxation, coordination, and flexibility training. The program was 8 weeks in length, and participants exercised for 60 minutes, 3 times per week. Those in the aerobic group exhibited an increase in PWC compared with those in the nonaerobic group. However, both groups experienced a significant reduction in depression score (p < .001), but there were no significant differences between the groups with respect to the magnitude of change in depression score (p > .10).
comment by Raemon
· score: 5 (2 votes) · LW
To do, by either me or someone else: look into some of these in more detail and think about the quality of the evidence and how it bears on JP's question.
Maybe a good practice is, if you are interested in doing that for one of these papers, reply here with your intent to do so (so you don't overlap with someone else) and then add a new Answer with your additional thoughts after spending 15-30 minutes on it
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