Alexis M. Leveille
WHAT STRETCHING DOES:
Stretching makes you more flexible. This is true and proven, you can absolutely reach further into your Range Of Motion (ROM) if you stretch regularly (1).
WHAT STRETCHING DOESN’T DO:
1. Stretching ALMOST NEVER makes your muscles longer, at least probably not the way 99.9% of people do it (2).
2. Stretching DOES NOT reduce injury risks according to a 2014 systematic review (2).
3. Stretching DOES NOT meaningfully reduce post-exercise muscle soreness according to a 2011 systematic review (3).
4. Stretching DOES NOT improve performance, and actually might make it worse SOMETIMES (5).
HOW DOES STRETCHING IMPROVE FLEXIBILITY THEN?
The main proposed mechanism behind the improvements in flexibility observed with stretching is that doing it regularly desensitizes your nervous system to that painful position. Basically, you get used to the pain of stretching, and your nervous system also sends fewer pain signals, so you can go further into your ROM (5).
Indeed, studies show that, despite the improved flexibility, when muscles are observed with ultrasound imaging, stretching does not change their fascicle length (FL) (muscle length) (1 & 5).
In fact, the only study showing that you can achieve significant long-term increases in FL via stretching is when the stretches are held for VERY long periods (6). Brace yourselves… that study asked he participants to maintain each stretch at least 450 consecutive seconds and that was at a very high stretching intensity 3X per week (for 8 weeks) which meant that for each stretch, participants had to reach the pain threshold… and stay there for over 7.5 minutes… (YIKES!).
WHAT ARE ECCENTRICS?
Eccentrics are a form of strengthening referring to the portion of the movement where your muscle is contracting while lengthening under an external load (gravity or added weights). For instance, when you go down during your back squat, your quads are contracting while getting longer (eccentric phase) whereas when you go up, your quads are contracting while getting shorter (concentric phase)
Let's look at biceps curls: the eccentric portion is when the dumbbell goes down whereas the concentric phase is when the weight goes down. An analogy I like is that if that the eccentric portion is like sliding down a rope, the concentric portion is going up the rope.
WHAT DO ECCENTRICS DO?
1. They ACTUALLY and CONSISTENTLY make your muscles longer as measured by ultrasound according to all six high quality studies included in a 2012 systematic review (1). More precisely, eccentrics create micro tears in your muscles which then grow back stronger AND longer via a process called sarcomerogenesis (more contractile units in series making the muscle longer, stronger and more extensible). This is relevant because unlike (most) static stretching it allows you to ACTUALLY make your muscles longer (and faster and way more comfortably then maintaining a 7.5 minute static stretch into pain!).
2. They make you stronger as much as other types of strengthening exercises if not more, according to a a 2009 systematic review (7).
3. The lead to hypertrophy (muscle growth) as much as other strengthening exercises (7).
4. Since they are strengthening exercises, they can reduce overuse injury by as much as 50% and traumatic injuries by 66% according to the 2014 systematic review investigating injury prevention programs (2). N.B.: that same review revealed a 0% difference in injury prevention for stretching.
5. They improve power, speed and strength performance for athletes according to a 2017 systematic review (8).
HOW SHOULD DO I DO ECCENTRICS IF I WANT TO BECOME MORE FLEXIBLE?
Although the protocols and dosage used by the various studies included in the (O’Sullivan et al., 2012) review (1) were variable, most of them shared the following characteristics: .
A) High loads: since your goal is to create microscopic muscle tears via eccentric contractions, you want the weights to be heavy enough that you are near the volitional failure point (the point where you can’t lift the weight anymore nor control its descent).
B) Slow eccentric phase (usually defined as at least 3 s).
C) Some of the studies included an isometric (muscle contraction without any joint movement) pause of a few seconds at the end of the movement, when the muscle is in a stretched position. .
D) Number of reps was variable, usually going from 5-10, so I suggest you stick to what your prefer as the number of reps is usually not that big of a factor for muscle changes (at least regarding hypertrophy and strength) as long as you reach volitional failure or close (1-2 reps left in the tank at most) (9).
I criticize stretching a lot and it’s not because I have a personal vendetta against it or anything; I just like to use my time efficiently, and I think that stretching is not as useful nor as effective as most people think it is if you compared to other things (like eccentrics) that can achieve similar objectives (increased flexibility) in less time, with less pain and with much more widespread benefits, i.e., actual muscle lengthening, drastic reduction in injury, improved sports performance, strength and hypertrophy and reduced mortality.
In short, I don’t think stretching is useless, I just think it’s superfluous and that it doesn’t do what most people think it does and - consequently - leads to a lot of people wasting (regarding their objectives) 30 min in the gym stretching rather than doing something more productive (like more strengthening or cardio). If you really like to stretch for the sake of it, go ahead, but I think it should not be a priority for most people, especially when their time is limited.
- O'sullivan K, Mcauliffe S, Deburca N. The effects of eccentric training on lower limb flexibility: a systematic review. Br J Sports Med. 2012;46(12):838-45.
- Lauersen JB, Bertelsen DM, Andersen LB. The effectiveness of exercise interventions to prevent sports injuries: a systematic review and meta-analysis of randomised controlled trials. Br J Sports Med. 2014;48(11):871-7.
- Herbert RD, De noronha M, Kamper SJ. Stretching to prevent or reduce muscle soreness after exercise. Cochrane Database Syst Rev. 2011;(7):CD004577.
- Barbosa GM, Trajano GS, Dantas GAF, Silva BR, Vieira WHB. Chronic Effects of Static and Dynamic Stretching on Hamstrings Eccentric Strength and Functional Performance: A Randomized Controlled Trial. J Strength Cond Res. 2019;
- Weppler CH, Magnusson SP. Increasing muscle extensibility: a matter of increasing length or modifying sensation?. Phys Ther. 2010;90(3):438-49.
- Freitas SR, Mil-homens P. Effect of 8-week high-intensity stretching training on biceps femoris architecture. J Strength Cond Res. 2015;29(6):1737-40.
- Roig M, O'brien K, Kirk G, et al. The effects of eccentric versus concentric resistance training on muscle strength and mass in healthy adults: a systematic review with meta-analysis. Br J Sports Med. 2009;43(8):556-68.
- Douglas J, Pearson S, Ross A, Mcguigan M. Chronic Adaptations to Eccentric Training: A Systematic Review. Sports Med. 2017;47(5):917-941.
- Lacerda LT, Marra-lopes RO, Diniz RCR, et al. Is Performing Repetitions to Failure Less Important Than Volume for Muscle Hypertrophy and Strength?. J Strength Cond Res. 2019.