Stretching Scientifically

Stretching Scientifically by Thomas Kurz is, according to some (including Jujimufu from Legendary Flexibility), the definitive book on stretching.

Also see this old school video for the book.

Here are my notes from the book:


  • The goal is strength and flexibility (together)
    • I like this approach versus something like yoga wherein much of it you only work on flexibility without strength
  • The goal is also to be able to do a full stretch without warm-up (e.g. splits)

Chapter 1 – Flexibility in Sports

There are six kinds of flexibility

  1. Dynamic active flexibility (only using muscles of the moving body part)
    • e.g. kicking high, moving arms around
  2. Dynamic passive flexibility below pain threshold (with external assistance)
  3. Dynamic passive flexibility over the main threshold (max limit with external assistance)
  4. Static active flexibility (only using muscles of stretched body part to hold a stretched position)
    • e.g. raise one leg, stretch arms behind back
  5. Static passive flexibility below pain threshold (with external assistance)
    • e.g. hold leg when raised, press arm against wall
  6. Static passive flexibility over the main threshold (max limit with external assistance)

But in training you normally only practice the bold ones.

There is a difference between the passive (more) and active (less) flexibility, this is called the ‘flexibility reserve’.

You want to do stretches specific for your sports. So for me that is weightlifting (and somewhat powerlifting) in which I will mostly need dynamic active flexibility, e.g. having flexiblity and strength in a snatch or squat.

Too much flexibility (without strength) is detrimental to your sports performance. Luckily I won’t have this problem for some time, but good to keep in mind. Olympic weightlifting is mentioned on page 8, again not an issue I currently have (being too flexible).

There is no clear connection between flexibility and injury. This really differs between sports and athlete.

An imbalance in muscle strength is not good for injury risk. So also do stretches in the opposite/non-used direction to keep balance.

Do stretches after sports, besides some warm-up (before). Do stretches a few hours after sports if you went hard (you don’t want to compound the damage you’re doing to your muscles).

Chapter 2 – How to Stretch

The goal is to do stretches at full length without warming up, but don’t abuse that.

It should be easy to do (stretch, gain flexibilty), but common mistakes are:

  • wrong warm-up: static stretching doesn’t warm you up enough!
  • wrong training load: don’t overdo it!
  • wrong sequence of efforts: (explained in other book…)
  • wrong methods: again overtraining

Methods of stretching:

  • Dynamic stretching: moving parts of your body and gradually increasing reach, speed of movement, or both
    • E.g. leg raises, arm swings
    • Sets of 8-12 reps
    • If tired after few sets, stop! (fatigue is bad – decrease in the amplitude of your movements)
    • Do only number of reps that you can do without diminishing range of motion
    • If you reach the maximum range you have, do only a few more reps (so stop before the range becomes smaller again)
    • Don’t stop at end of range (that is static active stretches), move in&out
    • Goal/outcome: increase dynamic active flexibility
    • Ballistic stretching, with momentum (and weight) is counterproductive
    • Control the movement, even when going fast
  • Static active stretching: moving your body into a stretch and holding it there through the tension of the muscle-agonist (the muscles under stretch) in this movement.
    • 15 second is good
  • Relaxed stretching for static passive flexibility: best for increasing static passive range
    • Can be good against cramped muscles, but should be used sparingly (will damage them further)
  • Isometric stretching for static passive flexibility: same as above, plus strong tensions of stretched muscles (cause postcontractive relaxations)
    • tense the antagonist (muscle oppose to it)
    • Contract-relax (like videos from BodyweightWarrior)
    • Isometric stretching is best for increasing passive range of motion
    • Don’t overdo the training, don’t be very sore afterward (loss of strength and range of motion)

Do isometric stretching on day of strength workout (e.g. few hours after, or end of workout), static relaxed stretches on other days. Total days 3-5!

To develop passive mobility up to 90% of what is anatomically possible, for ankle and knee joints it usually takes up to 30 days, spine 60, hip 60-120. Wow! that is quick!

  • Passive stretches increase passive range, and also active range (but at same percentage, e.g. 80%)
  • Strength exercises close this gap
  • Doing both is best of course

How to do strength exercises for flexibility:

  • Weight that stretches, but isn’t too heavy
  • Start at stretched position, stop there for 3-5 seconds
  • Range of motion should be higher each rep

Early morning stretching

  • Make it part of your routine if you need flexibility (so do it)
  • Before breakfast
  • Few sets of dynamic movements
  • But first do non-maximum-stretch warm-up (e.g. jumping jacks/squats – or others for other bodyparts)
  • No isometric stretches in morning if you do strength later on
  • 30 minutes max for beginners, few minutes if already flexible
  • You shouldn’t get tired (no fatigue)
  • Goal: reset nervous regulation of the length of your muscles for the rest of the day

Stretching in your workout

  • Dynamic stretches at beginning of workout (as part of warm-up routine)
  • Static stretches in cooldown (isometric I would guess is best)
  • 10 minutes dynamic stretching in warm-up
  • Resemble the movement you will do in the workout
  • Start with warm-up of limbs (joint rotations – start in fingers, then hand, then arm)
    • End at toes (or other way around)
  • Then 5 minutes of jogging (in place) with some twists, leans, arm swings, skips, etc
  • Then dynamic stretches
    • leg raises (10-12 reps) to the front, sides and back
    • Arm swings (5-8 reps)
    • As many sets as to reach maximum range (30+ reps at least, or less if really trained)
  • Don’t do static stretches in warm-up!
  • Then do very specific stretches (e.g. pass-through, barbell on knee stretch, overhead squats)
    • Warm up for each exercise that needs stretching
  • After exercises, do the isometric or relaxed stretching
    • Caution: pick only one isometric stretch per muscle group and repeat 2-5 times, go to max of mobility
    • Then relaxed stretching
  • Then walk for a few minutes to help the neural regulation of your muscles to return to normal

Much less work is required to maintain flexibility, than to get it.

Don’t use partners in stretching, this is dangerous!

(parts about kids and elderly)

Note: one of each type of stretch for a given group of muscles is usually enough. So, in a workout you would do one dynamic, one isometric, and one relaxed stretch for e.g. hamstring.

Chapter 3 – Dynamic Stretching

Dynamic flexibility, is best made through dynamic stretching. It depends on the ability to combine relaxing the extended muscles with contracting the moving muscles.

Don’t do dynamic stretching when muscles are tired.

It’s most effective if you do it daily, two or more times a day! (30 reps).

You can reach your potential in 8-10 weeks, after that change is slow (not muscles but ligaments/bones).

Dynamic stretching is done in sets, increasing in range, 5-15 reps per set.

The bigger the muscle, the more reps/sets are needed. But stop at fatigue.

Do it in the morning and before sports (i.e. that way I can do it two times most days).

Start slow, then increase range. Lead/lift the limbs instead of throwing them. Control throughout the full range.

Breathe as you stretch (in and out timed to back/forth). Breathe out when flexing your spine/compressing rib cage.

Examples of dynamics stretches (bold what could be useful):

  • Neck: nothing special besides warm-up (joint rotations)
  • Arms:
    • Arm rotations (circles)
    • from hug-self to arms in back, face palms up for extra stretch
    • min 10 reps per set, 30-40 reps total
  • Legs: many sets needed in beginning, eventually only one
    • Kick them up high
    • Or to the side
    • Or kick back, body leaning forward and supported (e.g. hands on chair)
    • support can also be used for first two
    • min 15 reps per set, 30-40 reps total
  • Trunk: best sitting down, rotate trunk
    • Rotate sideways
    • Side-bends
    • Forward bends (back rounded)
    • Bends on the back (lay on stomach, hands ground)
    • min 30 reps (total?), 40-70 recommended

Chapter 4 – Static Active Stretching

Static active stretching refers to stretches where you are actively supporting the body part with that muscle/body part itself but trying to go to the maximum stretch possible, you can move back and forth a bit.

Think of it like the last chapter, but try and hold at the extended position.

I think this applies somewhat to holding the positions of weightlifting, but maybe also that these can be best done during weightlifting itself.

Not sure really if I need this.

Chapter 5 – Isometric Stretching

Static stretching (this chapter and the next) are concerned with lengthening the maximum flexibility (and the active ones to make the gap smaller).

Static stretching may increase when your muscles are somewhat fatigued. This is why you should do static stretching at the end of a workout.

Isometric stretching is the fastest method of developing static passive flexibility. It also improves active flexibility as well as strength in concentric, isometric, and eccentric actions. There are indications that it causes longitudinal growth of muscle fibers.

It’s not for kids. And not if muscles are weak. And not if doing it with too much force/weight.

Pick one isometric stretch per muscle group and repeat it 3-5 times. Using as many tensions per repetition as it takes to reach the limit of mobility that you now have.

  • 4x per week
  • 10-15 minutes per day
  • tensions of 5-6 seconds (x3-5 reps)
  • increase tension per second (max at 3-4 seconds to end)
  • longer tension if progressing
  • if plateau, then focus on strength, flexibility will follow again
  • if overstretched, do only relaxed stretching (next chapter)
  • don’t do if you feel sore

Weekly training tips. Do speed/technical session day before strength/endurance (heavy) day.

There are three methods of doing isometric stretches:

  1. Stretch the muscle, wait for the body to adjust, x3, do short strong tensions, and quick relaxations, x3-5, then hold last tension 30 sec
  2. Stretch as far as you can, hold tension until muscle spasms, decrease stretch, repeat and hold up till 5 min (wtf XD)
  3. (this one is recommended) Stretch but not to maximum, tense for 3-5 sec, then within 1-5 sec, stretch again, tense again, repeat until can’t stretch further
    • (works better because tension can be higher when not maximally stretched)
    • For the greatest effect during a stretch tense the muscles opposing the stretched ones
    • Increase time of last tension to 30 seconds (over time)
    • Rest at least 1 minute, repeat set (3-5 sets total)


  • Breathe normally, abdominal
  • Inhale prior to tension
  • Exhale or hold when tensing
  • Exhale during the last (long) tension

Selecting stretches depends on which muscle you feel first when trying to do a movement. E.g. when trying to hold a barbell/stick overhead in a squat (narrow grip), what is holding you back first/most? (ankles)

The stretches (ones that are somewhat applicable)

  • Hands: hold back or forth, tense against the other hand holding it
  • Arms, shoulders, chest: hold stick overhead, tense all stretched muscles, make grip more narrow, repeat (hold 30 sec)
  • Arms, shoulders, chest: hold stick behind back, one arm up, one arm down, do on both sides, without stick eventually
  • Inner thigh: sumo squat (for side splits), toes forward, chest up, buttocks at same level as knees, tense inside of tighs (relax, go wider, repeat)
    • Other version: with chair/surface on one side, raise higher
    • Or do a full side split: tense side of thighs again.
  • Outer thigh: to balance the last one, outer thigh and hip stretches – lay on back, stretch one leg across, tense and stretch further (use yellow band to stretch)
  • Front/back thigh: for front-splits, see page 76 (sit on knee and bend forwards, or grab leg behind you standing or same sitting position)
  • Calf: grab foot, pull towards you, resist with foot, relax (pull toes closer), repeat, last tension 30 sec
  • Calf: can also do deep squats and lunges for this!
  • Hamstrings: legs and chest closer to each other either standing (one leg raised on chair/platform), sitting (bend upper body forward), or laying down (pull leg towards you)
    • Keep back straight
    • Again, tense, relax, deeper, repeat
    • Tip: do good mornings for hamstring flexibility and strength
  • Trunk: side bends (standing or sitting), move only to the side (not forward/backward/twist)
  • Lower back/hamstrings: sit or stand and grab back of legs, tense against them (standing one leg, or both, or sitting both)
  • Abdomen stretch: lay face down, push up with arms, tense abdomen and relax, repeat
    • Make more intense by grabbing feet (counter spasms in back with counter-stretch)

You need enough rest between isometric stretches, and supplement them with the dynamic stretches.

Chapter 6 – Relaxed Stretching

Relaxed stretches are less effective than isometric stretches. But, they can be done when you’re tired. Alas you don’t develop strength with relaxed stretches, and take a long time to develop flexibility.

Do relaxed stretches at the end of the workout (after isometric, before walking a few minutes). You can also do them whenever without warm-up.

Relaxed stretches decrease strength for 5 minutes and contractile force up to 60 minutes.

Instead of tension on the muscles (isometric stretches), find positions where you can fully relax them (e.g. in splits, support your body weight).

If you’ve found the fully stretched position, staying in it for 30 seconds is optimal. Can repeat after 60 seconds.

See page 87 (pdf, 77 of book) for the relaxed stretches.

Chapter 7 – Sample Workout Plans

The order of stretches is: dynamic, static active, isometric, relaxed. You don’t always need to do all of them (e.g. static active probably not so much).

The rest of the chapter is examples of one workout (the stretches before and after) for different sports.

Chapter 8 – All the Whys of Stretching

strong opinion

The chapter lists more reasons why you should want flexibility (e.g. longer range of movement is stronger movement, lower injury risk).

Warm-up needs to be specific for the muscles you will use (e.g. jogging is good for ankles, not for trunk).

“Flexibility improves from day to day, strength from week to week, speed from month to month, endurance from year to year”

Flexibility is not inborn, but requires (and works by) training.

Static stretching (isometric, relaxed) stretching after a workout helps because it allows more blood flow and relieves muscle cramps.

Muscles can typically stretch between 70-130% of resting length. By stretching you increase the amount of sarcomeres (thus lengthening the muscles).

The chapter also includes two tests to see if your ligaments can support front- and side splits.

Your muscles are probably already long enough, it’s just the mind-body connection that you need to work on (and that is why dynamic stretches are good at working on closing that gap).

Chapter 9 – Q&A on Stretching

Some Q&A.

One note: do relaxed stretching after endurance (burpees?) workout, not isometric.

No rest needed between dynamic exercises (i.e. go back and forth between legs).

After doing 3-5 sets per muscle(group) of isometric stretches (after workout), do about 1-2 minutes of relaxed stretching.

Preferably only do static stretches at the end of a workout (with warm muscles).

Again note on training schedule (more in other book), first technical/speed, then strength, then endurance.

Stretches (really hard) are not good in between sets of strength exercises.