Training across a life

People are told not to lift for all sorts of reasons. Women because they'll get bulky, older people because they're too frail to gain anything, pregnant women because it's dangerous, children because it stunts growth, and anyone with a bad back because rest is safer. For most of those groups, the guidance read for this course says yes, with conditions, and the worry about women getting bulky is a claim nobody here measured. This lesson goes through each group and gives you the permission and the conditions together, because either one on its own misleads, and it tells you who to ask about the parts no course can decide for you.

That box matters more here than anywhere else in the course. Lesson 1 promised that this course would show healthy adults how to train, inside named general guidance, and would stop short of prescribing for a pregnancy, a child, a medical condition or an injury. This is the lesson where that line gets walked. So each section below says what the guidance supports and what condition comes with it, and none of it is a plan for your pregnancy, your child, your blood sugar or your back. The plan for those is made with someone who can examine you.

First, whose evidence is it?

Lesson 4's table showed who the main strength literature trained: untrained people in their twenties, more often men, for two or three months. The groups in this lesson are mostly outside that. Even the authors of lesson 3's endurance study, which trained only young men, mark where their result stops: "Further research will elucidate whether current conclusions can be extrapolated to populations including females, older individuals and/or cardio‐metabolic patients."² A similar caution fits much of the literature behind lessons 4 to 7.

So each section below names a different body of evidence, with its own trials and its own guidance written by the specialists for that group (obstetricians, diabetes associations, falls researchers). That is also why the conditions differ from group to group.

One general answer comes first. The 2026 American College of Sports Medicine (ACSM) position stand, which lessons 4 to 7 used, did not separate its evidence by age and says "our recommendations are evidence-based across all ages".¹ It also says "Resistance training is safe for healthy adults of all ages".¹ The word to hold on to is healthy. Most of what follows is about people for whom that word needs checking.

Women

The claim people usually make about women and lifting isn't that they can't gain. It's that lifting will make a woman bulky. Start with what lesson 4 already gave you.

For the per cent, there is Hubal and colleagues' 2005 study of 585 people, which lesson 4 used for its range of responses. This course read its abstract; it trained one arm's elbow flexors for 12 weeks. It reported both halves, and they point different ways: "Men experienced 2.5% greater gains for CSA (P < 0.01) compared with women. Despite greater absolute gains in men, relative increases in strength measures were greater in women versus men (P < 0.05)."³ CSA is cross-sectional area, the size of the muscle measured across it. The authors' own summary: "Men had only a slight advantage in relative size gains compared with women, whereas women outpaced men considerably in relative gains in strength."³ So in this one large trial men's muscles grew a little more, men added more in absolute terms, and women's strength rose more as a share of where they started. Both halves are true at once, which is why "women gain less" and "women gain more" can each be defended by somebody quoting half a sentence.

As for "bulky", nothing read for this course measured it. Bulky is a claim about absolute size and about appearance, and these studies measured change in muscle size and strength.³ The honest sentence is: on these measures, women's muscles respond much as men's do for where they start, and how much that changes how anyone looks is not something these studies tested. Lesson 10 comes back to appearance goals as reasons people train that this course doesn't judge.

What conditions attach? For a healthy woman, none beyond the ones for everybody: the box at the top, and lessons 5 to 8. Pregnancy and low bone mass have their own sections below.

Older adults

The belief here is that past a certain age the body can't gain anything worth the risk. Lesson 4's exercise gave you two analyses in older people, one averaging about seventy and one aged 75 and over, and in both, strength rose substantially.

A third analysis puts the gains in kilograms. Peterson and colleagues' 2010 meta-analysis, read in full, pooled 47 studies of 1,079 people aged 50 or over, randomised and non-randomised trials together. Strength rose by between 9.8 and 31.6 kg (22 to 70 lb) across the lifts measured, "and percent changes were 29 ± 2, 24 ± 2, 33 ± 3, and 25 ± 2, respectively for leg press, chest press, knee extension, and lat pull."⁴ That is roughly a quarter to a third on each machine. Their conclusion: "RE is effective for improving strength among older adults, particularly with higher intensity training."⁴ RE is resistance exercise.

Apply the course's question before you take that home. Whom: people over 50, in studies of mixed design. How long: the studies varied. Measured on what: four machine lifts. Where people were tested on the machines they trained on, which is usual in this field (the 2026 stand defines its strength numbers that way), lesson 4's point applies: part of the gain is skill at the machine. So read it as "older adults got much better at the lifts they trained", which is still a large and useful result. It says nothing about why they got stronger, and this course does not assume the answer is muscle growth; lesson 4 left that dispute open.

What changes with age

Every analysis of older adults read for this course found strength still rises with training: Peterson's here, and in lesson 4's exercise Borde's, averaging about seventy, and Grgic's, aged 75 and over with a separate result for those 80 and over.⁴ The review read on children, later in this lesson, calls supervised training effective as well as safe.¹² For pregnancy and the conditions after it, the sources read are about whether training is safe and what it needs, not about how much it builds. So this lesson's working reading, which is the course's and not any one source's, is that what differs from group to group is mostly what can go wrong along the way, and so the conditions differ.

For older adults, the 2026 stand names one such thing: "It may also be that lifting to fatigue is inadvisable for certain populations (e.g., older individuals) due to risks to vascular health and an increased risk of injury resulting from poor form".¹ Lesson 5 showed that going to failure wasn't needed for gains, so stopping short gives up little.

Falls, and a limit this course has to admit

For many older people the reason to train isn't a bigger lift. It's not falling. WHO's guidelines say older adults should do "varied multicomponent physical activity that emphasizes functional balance and strength training at moderate or greater intensity, on 3 or more days a week", to prevent falls among other things, and lesson 1 promised that this lesson would take that up.⁵

The best single test of it is a 2019 Cochrane review by Sherrington and colleagues: 108 randomised trials, 23,407 people aged 60 and over living in the community, mean age 76, 77 per cent women. This course read its abstract and plain-language summary in full. Across all types of exercise against a control: "Exercise reduces the rate of falls by 23% (rate ratio (RaR) 0.77, 95% confidence interval (CI) 0.71 to 0.83; 12,981 participants, 59 studies; high‐certainty evidence)."⁶

Then it splits the result by type of exercise, and this is where a strength course has to be honest about its own tool. Balance and functional exercise, meaning practice at balance and at everyday movements like standing up and stepping, reduced falls with high certainty. Programmes combining several types, "most commonly balance and functional exercises plus resistance exercises", probably reduced them. And for strength training alone: "We are uncertain of the effects of programmes that are primarily resistance training, or dance or walking programmes on the rate of falls".⁶

Uncertain is not the same as ineffective. It means the review could not tell. The American Heart Association's 2023 statement on resistance training, which this lesson uses again below, is more confident: "RT can reduce the risk of falls and injury from falls (eg, fractures) in older adults. RT programs that incorporate balance-challenge exercises (eg, feet closer together, minimal hand support) may be the most effective in fall prevention."⁹ RT is resistance training. That is a narrative statement citing one reference, not a graded review, and the Cochrane review is the graded test. Where the two overlap they agree: strength work with balance built into it. So if falls are your reason to train, a plan of lifting alone is not what the evidence tested best, and balance work is what WHO's "multicomponent" is asking for. On safety: "Where reported, adverse events were predominantly non‐serious."⁶

Margit: a first month at 72

Margit is constructed for teaching, and no source read for this course describes her.¹⁷ She's 72, has no diagnosed conditions and no symptoms, walks to the shops most days, and has never lifted anything on purpose. A friend broke a hip in a fall last winter, and Margit wants to start before the same happens to her. Take her through it the way this course would, starting with the step you already have the tools for.

Step 2, what the evidence supports for her goal. Her goal is not falling. From the section above, the strongest evidence is for balance and functional exercise, and mixed programmes that add strength work probably help too. So her plan needs both, on three or more days a week in WHO's terms, and strength work on at least two of them.⁵⁶

Step 3, the strength part. Lesson 7's two-day plan was built for a healthy beginner inside the 2026 stand, and Margit is a healthy beginner: four movement slots, two sets each, working towards stopping two or three reps short of failure. One thing changes for her, and one is worth adding. The stopping point matters more, because of the stand's caution about older people and failure. And the AHA's statement gives a lighter starting point for anyone new to resistance training than lesson 7's plan settles at: "When beginning a new RT program, an initial intensity should correspond to 40% to 60% of 1-RM".⁹ Margit has no one-rep maximum to take a percentage of, and this course doesn't ask a beginner to test one, so on this course's reading that means loads she could lift many more times than she does, for the first few weeks. The chair for her squat is one without wheels, backed against a wall.

Step 4, the balance part. The Cochrane review pooled many different programmes, and this course read no programme's detail. The National Institute on Aging's booklet for older adults, read in full, gives a starting place: "Aim for about three sessions of balance exercises each week", with examples such as "Standing on one foot" and "Practicing standing from a sitting position", and a safety tip: "Have a sturdy chair, person, or wall nearby to hold onto for support."⁷ Those are examples, not a programme. Making balance work harder, safely, is for a physiotherapist, a qualified exercise professional, or a class her doctor can point her to.

Put together, a first month could look like this. It is this course's sketch, inside the guidance above, with what each line rests on.¹⁷

• Weeks 1 and 2. Two strength days, say Monday and Thursday, run as lesson 7's first sessions: one or two sets of about five of each movement, well short of hard (lesson 7's first-session convention, kept for two weeks for the AHA's light start). Her walks carry on as before. Balance examples from the booklet on three days, beside the sturdy chair (the NIA's frequency).
• Weeks 3 and 4. The same two days, now two sets each of 8 to 12 reps, at a version she could clearly do many more times (lesson 7's sets and reps, kept light for the AHA's start). Balance on three days, and she has asked her doctor or a physiotherapist about a class (Step 4).
• After the month. She moves towards lesson 7's two or three in reserve, never to failure (the stand's caution), and keeps lesson 7's log.

Low bone mass: two answers that both hold

Osteoporosis is bone thin enough to break easily, and osteopenia is the milder stage before it. The belief is that people with either must not lift anything heavy. There is a trial that seems to say the opposite and a caution that seems to agree with the belief, and the point of this section is that both are right.

The trial is LIFTMOR, by Watson and colleagues in 2018, read at abstract level. Its authors say this kind of training "is not traditionally recommended for individuals with osteoporosis because of a perceived high risk of fracture."⁸ It took 101 postmenopausal women, aged 65 on average, with low to very low bone mass, "screened for conditions and medications that influence bone and physical function", for eight months. One group did "supervised HiRIT (5 sets of 5 repetitions, >85% 1 repetition maximum)", which is heavy lifting with impact work added (HiRIT stands for high-intensity resistance and impact training), twice a week for 30 minutes. The other did low-intensity exercise at home.⁸

Here's the sentence the whole trial rests on, in the authors' own words: "Contrary to current opinion, HiRIT was efficacious and induced no adverse events under highly supervised conditions for our sample of otherwise healthy postmenopausal women with low to very low bone mass."⁸ Every clause after "adverse events" is scope. Highly supervised. Otherwise healthy. This sample.

The caution comes from the AHA's statement, and it is not against lifting for bone. In its own voice the statement says "RT improves bone mineral density in the femoral neck and the lumbar spine in pre- and postmenopausal women."⁹ Its caution is for one group. In a paragraph that opens with people who "should seek physician consultation and medical clearance before starting an RT program", it says people with "severe osteoporosis" among others "may benefit from low- to moderate-intensity RT", and adds: "Machines are likely safer than free weights for these patients, and the guidance of an exercise professional may provide enhanced benefit."⁹

Put them side by side and see what each headline needs to drop.

• "Heavy lifting is safe for women with osteoporosis" drops LIFTMOR's supervision, its restriction to otherwise healthy women, and the severity of the bone loss. The AHA's caution is about severe osteoporosis, and the trial's abstract doesn't show that its result reaches that group.
• "Women with osteoporosis must not lift heavy" drops LIFTMOR's result altogether, in the group it did study.

Kept in scope, they're about different people under different conditions, and there is no contradiction to resolve. This course classes it as established within each scope and contested only if somebody drops the scope. What it means for a reader with low bone mass: heavy lifting with impact work has been shown to help, safely, in one trial, under close supervision, in women otherwise well, and that's exactly the arrangement to ask a doctor and a qualified professional about, before starting and not alone.

Pregnancy

The belief is that pregnant women shouldn't lift. The two guidelines read here encourage it, with conditions, and they're specific about both.

The American College of Obstetricians and Gynecologists' Committee Opinion 804, from 2020, read here in full as its web version: "Women with uncomplicated pregnancies should be encouraged to engage in aerobic and strength-conditioning exercises before, during, and after pregnancy."¹⁰ Its list of exercises found safe and beneficial includes "Resistance exercises (eg, using weights, elastic bands)".¹⁰ The Canadian guideline of 2019, whose recommendations this course read in full on the CSEP guideline page: "All women without contraindication should be physically active throughout pregnancy", and "Pregnant women should incorporate a variety of aerobic and resistance training activities to achieve greater benefits."¹¹ Its abstract sums up the evidence behind it: "The benefits of prenatal physical activity are moderate and no harms were identified".¹¹ WHO recommends the same, and adds a line that marks exactly where this course stops: "Clinical guidance should be sought for women with complications associated with pregnancy or delivery."⁵

The conditions start with the word each recommendation turns on: uncomplicated, without contraindication. Whether a pregnancy is uncomplicated is not something you can decide from a course. ACOG puts the step first: "A thorough clinical evaluation should be conducted before recommending an exercise program to ensure that a patient does not have a medical reason to avoid exercise."¹⁰ That is why the box at the top sends anyone pregnant to a doctor, and why lesson 1's PAR-Q+ says to hold off on stepping up activity while pregnant until you've talked to a practitioner or completed its follow-up form.⁷

The Canadian guideline lists absolute contraindications, the reasons to avoid strenuous exercise altogether. They include "ruptured membranes" (the waters breaking early), "premature labour", "unexplained persistent vaginal bleeding", "preeclampsia" (a pregnancy condition of high blood pressure and strain on organs) and "uncontrolled hypertension".¹¹ Even then it doesn't say stop moving: "Women with absolute contraindications may continue their usual activities of daily living but should not participate in more strenuous activities."¹¹ ACOG's own contraindication tables weren't in the version this course read, so the list above is the Canadian one.¹⁰

Several practical conditions come from the two guidelines. ACOG: "remain well hydrated, avoid long periods of lying flat on their backs", and "Contact activities with high risk of abdominal trauma or imbalance should be avoided."¹⁰ The Canadian guideline adds a symptom rule for lying down: "Pregnant women who experience light-headedness, nausea or feel unwell when they exercise flat on their back should modify their exercise position to avoid the supine position."¹¹ Supine means lying on your back. On effort, ACOG notes that both blunted and normal heart-rate responses have been reported in pregnancy, so "the use of ratings of perceived exertion may be a more effective means to monitor exercise intensity during pregnancy than heart-rate parameters", and it offers the talk test as another way.¹⁰ Both are lesson 2's tools. And "Pregnant women who were sedentary before pregnancy should follow a more gradual progression of exercise."¹⁰

ACOG is also open about a gap, and it's the strongest reason the cautious side has. In its section on elite athletes it says resistance training "was not considered a safe activity in early guidelines for exercise during pregnancy because of potential injury and possible fetal heart decelerations resulting from Valsalva maneuvers. Consequently, there is sparse literature on this topic".¹⁰ The Valsalva manoeuvre is lesson 6's breath-hold under strain, and lesson 6's rule against it applies here too. For elite athletes who want to keep training hard, ACOG advises them "to obtain approval from their health care providers, and to consider decreasing resistance load compared with prepregnant conditions."¹⁰ That is written for athletes, not for every pregnant lifter. But it tells you the permission is broad and the evidence on hard resistance training in pregnancy is thin.

Then the stop signs. ACOG's Box 3 is titled "Warning Signs to Discontinue Exercise While Pregnant", and these are its ten items, word for word:¹⁰

• "Vaginal bleeding"
• "Abdominal pain"
• "Regular painful contractions"
• "Amniotic fluid leakage"
• "Dyspnea before exertion"
• "Dizziness"
• "Headache"
• "Chest pain"
• "Muscle weakness affecting balance"
• "Calf pain or swelling"

Dyspnea is breathlessness, so the fifth means being short of breath before you've started. Some of these overlap with the box at the top of every lesson, and several of them are specific to pregnancy. Any one of them means stop the session and contact whoever is looking after the pregnancy.

Children and adolescents

The belief is that lifting damages the growth plates, the areas of growing cartilage near the ends of a child's long bones, and stunts growth. The review read here in full is Faigenbaum and Myer's 2010 review of resistance training in young athletes, and it's direct: "Of note, injury to the growth cartilage has not been reported in any prospective youth resistance training study that provided professional guidance and instruction." And: "Furthermore, there is no evidence that resistance training will negatively impact growth in height during childhood and adolescence."¹²

So where did the growth-plate worry come from? From real case reports, and the review says what went wrong in them: "most of these injuries were caused by improper lifting techniques, poorly chosen training loads or lack of qualified adult supervision."¹² It gives one case that makes the hazard plain: "a 9-year-old boy died at home when a barbell rolled off the bench press support and fell on his chest while he was “playing” with his older brother’s weights."¹² The danger the evidence points to is lifting without qualified supervision, and at its worst, equipment left where a child can play with it.

Which is why the permission and the condition arrive in the same sentence. Resistance training "can be a safe, effective and worthwhile activity for children and adolescents provided that qualified professionals supervise all training sessions and provide age-appropriate instruction on proper lifting procedures and safe training guidelines."¹² The condition is all sessions, qualified professionals, and instruction that fits the child's age.

What that means in practice: a supervised school or club programme, run by a qualified coach, is what the evidence describes. A bar and plates in the garage is not. And this course doesn't write a programme for a child; the coach does.

Common conditions

Each of these gets the same three questions: what the guidance supports, what condition attaches, and who has to be involved. None of it is a plan. This is a natural place to stop and come back.

Chronic low back pain

The belief is to rest it. The best evidence read here is a 2021 Cochrane review by Hayden and colleagues, abstract and plain-language summary read in full: 249 trials in adults with chronic non-specific low back pain lasting more than 12 weeks, mean age 43.7.¹³ "Non-specific" means, in the usual clinical sense, pain without an identified cause such as a fracture, a tumour or a trapped nerve.

Against no treatment, usual care or placebo, exercise reduced pain by 15.2 points on a 0 to 100 scale ("MD ‐15.2, 95% CI ‐18.3 to ‐12.2"), which the authors call "a clinically important difference", their threshold being 15 points.¹³ MD is the mean difference between the groups. Function improved less: "MD ‐6.8 (95% CI ‐8.3 to ‐5.3); this finding did not meet our prespecified threshold for minimal clinically important difference."¹³ Their conclusion carries its own hedge: "We found moderate‐certainty evidence that exercise is probably effective for treatment of chronic low back pain compared to no treatment, usual care or placebo for pain."¹³ Harms were "mostly minor harms, e.g. muscle soreness".¹³

So exercise helps pain modestly, just past the line the authors set for mattering, and function less. The review does not say which exercise is best. The condition is in the word non-specific: the finding is about back pain without a serious cause, and telling whether yours is that kind is a job for a doctor or a physiotherapist. That is this course's reading of the review's scope, not something the review tells readers to do.

Type 2 diabetes

The American Diabetes Association's 2016 position statement, read in full, supports lifting directly: "Adults with diabetes should engage in 2–3 sessions/week of resistance exercise on nonconsecutive days."¹⁴ Its clearance line is looser than ACSM's, the way WHO's was in lesson 1, and this course keeps the cautious one.

The conditions are specific, and each guards against a particular thing going wrong.

• Low blood sugar. "Exercise-induced hypoglycemia is common in people with type 1 diabetes and, to a lesser extent, people with type 2 diabetes using insulin or insulin secretagogues."¹⁴ Secretagogues are medicines that push the body to release more insulin. It can come late: in the statement's paragraph on low blood sugar at night, hypoglycaemic events "occur typically within 6−15 h postexercise", and "risk can extend out to 48 h".¹⁴ And "Some medications besides insulin may increase the risks of exercise-related hypoglycemia and doses may need to be adjusted based on exercise training."¹⁴ The AHA adds: "Patients should monitor glucose levels before and after RT sessions to prevent exercise-induced hypoglycemia."⁹ Adjusting a dose is a doctor's decision. Some diabetes tablets are secretagogues and some aren't, so for Margit's changed case above, which kind hers is, and whether its dose needs changing, is the question for her doctor.
• High blood sugar. The statement also notes that very intense efforts, heavy powerlifting among them, may push blood sugar up, especially if it starts high, and "Exercising with hyperglycemia and elevated blood ketones is not recommended."¹⁴
• A heart problem that doesn't hurt. The ADA's table of precautions warns that "exercise-induced ischemia may be silent in some with diabetes".¹⁴ Ischaemia is the heart muscle short of blood, which usually causes chest pain. Silent means it may not, so the box's warning signs can't be relied on alone, which is one more reason the box sends people with diabetes to a doctor first.
• Feet and nerves. "Physical activity done with peripheral neuropathy necessitates proper foot care", and the AHA says "Caution is advised for individuals with diabetic neuropathy".¹⁴⁹ Neuropathy is nerve damage, which can blunt the pain that would warn you of an injury.
• Eyes. Lesson 6 gave the ADA's and AHA's limits on breath-holding and high-intensity lifting for diabetic eye disease. They apply here.

High blood pressure

Lesson 6 covered the breathing side (the AHA's low to moderate loads with proper breathing for controlled hypertension, and the ADA's advice to avoid the Valsalva manoeuvre), the extended cool-down for people on blood-pressure medicine, and the PAR-Q+'s 160/90 threshold.⁹¹⁴⁷ Two things to add.

The benefit is real and modest. The AHA reports that resistance training lowers resting blood pressure by about 4 mm Hg systolic and 2 diastolic in healthy adults over 40, and by more in people with high blood pressure: about 6 and 5.⁹ (Millimetres of mercury, mm Hg, is the unit a blood pressure reading is given in.)

ACSM's 2004 position stand on hypertension, read at abstract level, puts resistance work second: endurance activity first, "supplemented by resistance exercise", and says people with controlled high blood pressure and no heart or kidney complications can take part but should be evaluated, treated and monitored closely.¹⁵ That stand is more than twenty years old, and the AHA statement is the newer of the two.

Osteoarthritis

The belief is that exercise wears the joint out. NICE's 2022 guideline, whose recommendations this course read in full, says the reverse: "the core treatments for the condition are therapeutic exercise and weight management (if appropriate), along with information and support."¹⁶ And: "For all people with osteoarthritis, offer therapeutic exercise tailored to their needs (for example, local muscle strengthening, general aerobic fitness)."¹⁶

The condition is in "tailored", and in a warning that saves people from giving up in the second week: "Advise people with osteoarthritis that joint pain may increase when they start therapeutic exercise." NICE goes on to say that "doing regular and consistent exercise, even though this may initially cause pain or discomfort, will be beneficial for their joints".¹⁶ The guideline covers osteoarthritis generally, not the knee in particular, and this course did not read the evidence review behind it. Tailoring is what a physiotherapist or doctor does; the guideline's word "offer" is addressed to them.

Heart disease, and the programmes this course leaves out

People with known heart disease who aren't already exercising are a group ACSM's model sends to a doctor before they start at any intensity, and lesson 1 said this lesson would name the clinical programmes the course leaves out. The main ones are cardiac rehabilitation, which is supervised exercise and education after a heart attack or heart surgery, and physiotherapy. Your doctor or specialist is the route into both. This course read no source on how either is organised, so that is as far as it goes.

The AHA statement does say something useful about the fear. On what the authors call limited data, a review of trials in people with coronary heart disease, 23 trials reporting adverse events with 1,174 people between them, found that "there were 63 nonfatal cardiovascular-related complications during AT training and testing, whereas only 1 occurred during RT training and none during RT testing", AT being aerobic training. The authors hedge it further: "one-third of the studies in this review did not include adverse event information".⁹ And lesson 6's caution from the same statement, about pacemakers and defibrillators before upper-body work, applies here.⁹

The pattern

The whole lesson fits in one table. Read across a row and notice that the right-hand columns are never about whether the body can adapt. The fourth column is this course's reading of what each condition is for, drawn from the sources above rather than stated by any of them.¹⁷

Where the sources measured it, the body adapted, and the conditions exist because each group has its own way of going wrong.

What people get wrong

"Lifting makes women bulky." Appearance wasn't measured; on the measures taken, women's muscles respond much as men's do for where they start.

"Older people can't gain strength." Gains ran to a quarter or a third on each machine in adults over 50, with clear gains past 75 and 80 in lesson 4.

"Lifting will stop an older person falling." The AHA says it can, but the Cochrane authors are uncertain for strength training alone, and both favour balance work built in.

"Women with osteoporosis must not lift." Supervised heavy lifting with impact work raised spine density in one trial of otherwise healthy women; for severe osteoporosis, the AHA says low to moderate loads may help.

"The LIFTMOR trial shows heavy lifting is safe with osteoporosis." Only under close supervision, in otherwise healthy women; it doesn't reach severe osteoporosis or training alone.

"Pregnant women shouldn't lift." ACOG and the Canadian guideline encourage strength work in uncomplicated pregnancies, after a clinical evaluation, with ten signs that mean stop.

"Children shouldn't lift, it stunts growth." No growth-plate injury in supervised prospective studies, and no evidence of an effect on height, with qualified supervision as the condition.

"Rest a bad back." For chronic non-specific low back pain, exercise probably reduces pain, by a modest amount.

Practice

Connections

Back. Lesson 1's screening model did most of the sorting in this lesson, and its box is the thread through every section. Lesson 4's question, trained whom, for how long, measured on what, explained why each group here needed its own evidence: the main literature trained young, often male, untrained people for a few months. Lesson 5's finding that failure isn't needed became a safety margin for older adults, lesson 6's breathing guidance became part of the conditions for high blood pressure, diabetes and pregnancy, and lesson 7's two-day plan became the frame for Margit's first month. Lesson 8's line between soreness and a warning sign is what Wen needs. From earlier courses, Memory's sample question is the first half of this lesson's opening section.

Forward. Lesson 10 is the last: it joins this course's question to the institute's claim sort and uses it on the popular claims about training, including the ones about appearance that this lesson set aside. First Aid and CPR, later in this term, starts from the warning signs in the box.

Go deeper

• US National Institute on Aging, Exercise and Physical Activity for Older Adults,
  2025. Free PDF, read here in full. Written for older adults themselves, by a government research body, and plainer than anything else cited in this lesson. Its balance pages are the starting place Margit's Step 4 uses.
• ACOG Committee Opinion 804, "Physical Activity and Exercise During Pregnancy and the Postpartum Period",
  2020. Free; this course read the full web text, though its contraindication tables weren't in the version read. Written for clinicians, which is useful: it shows what your doctor is being asked to check.
• Faigenbaum and Myer, "Resistance training among young athletes: safety, efficacy and injury prevention effects", British Journal of Sports Medicine, 2010. Free and read here in full. The growth-plate question traced to its case reports, and the supervision condition argued rather than asserted.
• Hayden and colleagues, "Exercise therapy for chronic low back pain", Cochrane, 2021. This course read the abstract and plain-language summary. The summary is written for patients, and it's a model of saying how big an effect is as well as whether there is one.

Sources

1. B. S. Currier, A. C. D'Souza, M. A. F. Singh and others, S. M. Phillips (last author), "Resistance training prescription for muscle function, hypertrophy, and physical performance in healthy adults: an overview of reviews", American College of Sports Medicine position stand, Medicine & Science in Sports & Exercise 58(4), 2026, pp. 851 to 872, doi 10.1249/MSS.0000000000003897, PMC12965823. Read level: full text of the article (introduction, methods, all results sections, Table 1 to Table 6 as rendered, discussion, limitations, disclosures); supplemental appendices not opened. Supports: "across all ages", the safety sentence, and the caution about lifting to fatigue in older people.
2. D. Montero and C. Lundby, "Refuting the myth of non-response to exercise training: 'non-responders' do respond to higher dose of training", Journal of Physiology 595(11), 2017, pp. 3377 to 3387, doi 10.1113/JP273480, PMC5451738. Read level: full text, read for the abstract and key points, Methods (participants, design, the non-response rule), the Figure 1 legend and the Limitations. Supports: the sample of young men and the authors' limitation.
3. B. M. Roberts, G. Nuckols and J. W. Krieger, "Sex differences in resistance training: a systematic review and meta-analysis", Journal of Strength and Conditioning Research 34(5), 2020, pp. 1448 to 1460, doi 10.1519/JSC.0000000000003521, abstract only; M. J. Hubal, H. Gordish-Dressman, P. D. Thompson and others, "Variability in muscle size and strength gain after unilateral resistance training", Medicine & Science in Sports & Exercise 37(6), 2005, pp. 964 to 972, PMID 15947721, abstract only. Supports: the outcome counts and summary sentence from Roberts, which reports effect sizes rather than per cents; Hubal's sex findings in both absolute and relative terms, and its conclusion on relative size and strength; and the point that neither tests "bulky". Nuckols, a co-author of Roberts, is the practitioner whose work lesson 7 uses.
4. M. D. Peterson, M. R. Rhea, A. Sen and P. M. Gordon, "Resistance exercise for muscular strength in older adults: a meta-analysis", Ageing Research Reviews 9(3), 2010, pp. 226 to 237, doi 10.1016/j.arr.2010.03.004, PMC2892859. Read level: full text (via NCBI). Supports: the 47 studies, 1,079 participants aged 50 or over, the design mix, the gains in kilograms and per cent, and the conclusion. Also, from lesson 4's exercise: R. Borde, T. Hortobágyi and U. Granacher, "Dose-response relationships of resistance training in healthy old adults: a systematic review and meta-analysis", Sports Medicine 45(12), 2015, pp. 1693 to 1720, PMC4656698, full text, mean age 70.4; and J. Grgic and others, "Effects of resistance training on muscle size and strength in very elderly adults: a systematic review and meta-analysis of randomized controlled trials", Sports Medicine 50(11), 2020, pp. 1983 to 1999, abstract only, aged 75 and over with a subgroup of 80 and over.
5. World Health Organization, *WHO guidelines on physical activity and sedentary behaviour*, Geneva, 2020, ISBN 9789240015128, handle 10665/336656. Read level: full text downloaded; the adult, older-adult, pregnancy and chronic-condition recommendation boxes and good practice statements read closely. Supports: the older-adult multicomponent recommendation and the pregnancy sentence on clinical guidance.
6. C. Sherrington, N. J. Fairhall, G. K. Wallbank and others, "Exercise for preventing falls in older people living in the community", Cochrane Database of Systematic Reviews 2019, CD012424, doi 10.1002/14651858.CD012424.pub2, PMC6360922. Read level: abstract and plain-language summary read in full. Supports: the sample, the overall result, the results by type of exercise, and the adverse-events sentence.
7. Screening. D. Riebe, B. A. Franklin, P. D. Thompson and others, "Updating ACSM's recommendations for exercise preparticipation health screening", Medicine & Science in Sports & Exercise 47(11), 2015, pp. 2473 to 2479, doi 10.1249/MSS.0000000000000664, abstract only, with the algorithm read in full as reproduced in G. P. Whitfield, D. Riebe, M. Magal and L. Liguori, Medicine & Science in Sports & Exercise 49(10), 2017, pp. 2056 to 2063, PMC7059860, full text. US National Institute on Aging, Exercise and Physical Activity for Older Adults, 2025 (linked in Go deeper), full text. D. E. R. Warburton and others, on behalf of the PAR-Q+ Collaboration, The Physical Activity Readiness Questionnaire for Everyone (PAR-Q+), 2025, full text (all four pages). Supports: the branches applied to Margit, the NIA's older-adult sentence as lesson 1 quoted it and its balance pages (frequency, examples, the sturdy-chair tip), the PAR-Q+'s over-45 condition, pregnancy delay rule and blood pressure threshold.
8. S. L. Watson, B. K. Weeks, L. J. Weis, A. T. Harding, S. A. Horan and B. R. Beck, "High-intensity resistance and impact training improves bone mineral density and physical function in postmenopausal women with osteopenia and osteoporosis: the LIFTMOR randomized controlled trial", Journal of Bone and Mineral Research 33(2), 2018, pp. 211 to 220, doi 10.1002/jbmr.3284. Read level: abstract only. Supports: why the trial was novel, the sample and its screening, the two programmes, the bone density results, the adverse event and the authors' scope sentence.
9. A. E. Paluch, W. R. Boyer, B. A. Franklin and others, "Resistance exercise training in individuals with and without cardiovascular disease: 2023 update", American Heart Association scientific statement, Circulation 149(3), 2024, pp. e217 to e231, doi 10.1161/CIR.0000000000001189, PMC11209834. Read level: full text. Supports: falls, bone density in women, the starting intensity, the severe osteoporosis sentences and the paragraph on consulting a physician they sit in, glucose monitoring, the neuropathy caution, controlled hypertension, the blood pressure reductions in healthy adults over 40 and in hypertension, extended cooldowns, the complication counts with their lead-in and hedge, and the pacemaker caution.
10. American College of Obstetricians and Gynecologists, Committee on Obstetric Practice, "Physical activity and exercise during pregnancy and the postpartum period", Committee Opinion No. 804, April 2020, acog.org. Read level: full text of the web version. Contraindication tables did not come through in the text extraction and were not read. Supports: the recommendation for uncomplicated pregnancies, the clinical evaluation, Box 1's resistance exercises, Box 3's ten warning signs, hydration and lying flat, contact activities, perceived exertion and the talk test, the gradual progression for sedentary women, and the elite-athlete passage on resistance training.
11. M. F. Mottola, M. H. Davenport, S. M. Ruchat and others, "2019 Canadian guideline for physical activity throughout pregnancy", British Journal of Sports Medicine 52(21), 2018, pp. 1339 to 1346, doi 10.1136/bjsports-2018-100056. Read level: abstract read; the recommendations and contraindication lists read in full on the CSEP guideline page. Supports: the abstract's summary of benefits and harms, the recommendations quoted, the absolute contraindications and the supine position.
12. A. D. Faigenbaum and G. D. Myer, "Resistance training among young athletes: safety, efficacy and injury prevention effects", British Journal of Sports Medicine 44(1), 2010, pp. 56 to 63, doi 10.1136/bjsm.2009.068098, PMC3483033. Read level: full text. Supports: the growth cartilage and height sentences, the injury rates and the retrospective design of that study, the causes of the reported injuries, the case of the 9-year-old, and the supervision condition. An international consensus statement on youth resistance training followed: R. S. Lloyd, A. D. Faigenbaum, M. H. Stone and others, "Position statement on youth resistance training: the 2014 international consensus", British Journal of Sports Medicine 48(7), 2014, pp. 498 to 505, doi 10.1136/bjsports-2013-092952, abstract only. The abstract doesn't give its recommendations, so this lesson reports none.
13. J. A. Hayden, J. Ellis, R. Ogilvie, A. Malmivaara and M. W. van Tulder, "Exercise therapy for chronic low back pain", Cochrane Database of Systematic Reviews 2021, CD009790, doi 10.1002/14651858.CD009790.pub2, PMC8477273. Read level: abstract and plain-language summary read in full. Supports: the sample, the pain and function results with the authors' threshold, the conclusion and the harms. The gloss on "non-specific" and the reading that telling which kind of pain you have is a clinician's job are this course's, as the body says.
14. S. R. Colberg, R. J. Sigal, J. E. Yardley and others, "Physical activity/exercise and diabetes: a position statement of the American Diabetes Association", Diabetes Care 39(11), 2016, pp. 2065 to 2079, doi 10.2337/dc16-1728, PMC6908414. Read level: full text read from the PMC HTML page. Supports: the resistance recommendation, hypoglycaemia and its timing, medicines, high blood sugar with intense exercise, silent ischaemia, foot care with neuropathy, and the Valsalva advice.
15. L. S. Pescatello and others, "Exercise and hypertension", American College of Sports Medicine position stand, Medicine & Science in Sports & Exercise 36(3), 2004, pp. 533 to 553. Read level: abstract only. Supports: resistance exercise as a supplement to endurance activity, and evaluation and monitoring for people with controlled hypertension.
16. National Institute for Health and Care Excellence, *Osteoarthritis in over 16s: diagnosis and management*, NICE guideline NG226, 19 October 2022, recommendations. Read level: recommendations chapter, full text; evidence review C not read. Supports: recommendations 1.2.2, 1.3.1 and 1.3.3, and the point that the guideline covers osteoarthritis generally.
17. The course's own constructions, each labelled where it appears in the body. Margit is invented, and the body says so where she first appears; her first month is this course's sketch, labelled line by line with what it rests on. Kofi, Ines, Wen and Leon are invented, as the exercise says. The working reading that what differs between these groups is mostly what can go wrong, and the table's column on what each condition guards against, are this course's summary of the sources above, said as such in the body.