If you work out regularly, you've probably wondered at one point or another if improving your flexibility can help you get stronger. And, does flexibility help you gain muscle? Does increased flexibility help you lose fat? Does flexibility help you improve your performance? What is the best way to improve your flexibility? What about stretching? The list of questions goes on.

The answer to most, if not all of these questions normally always starts with, 'it depends'.  

As with everything, context is key. Take for example the first question of whether flexibility helps you get stronger. Well, this really depends on your current levels of flexibility and what getting stronger actually means to you.  

If you had a goal of increasing your 3 competition lifts as a powerlifter, then I would likely advise you that increasing your flexibility is likely to produce limited returns if any for your overall goal (2).  However, if your goal was to increase your strength for holding complex gymnastic positions then my answer may be completely the reverse (2). So, context really is key.

Define flexibility in physical fitness

Define flexibility in physical fitness

Flexibility is defined as the range of motion of the muscle(s) and connective tissues at a joint or group of joints (1). This might be something like whether or not a person can touch their toes. As a Personal Trainer, it's in my opinion that if you find yourself struggling to touch your toes, then you probably should spend some time improving your overall flexibility regardless of your training goals.

The more flexible the better, right? Well, that is something that is up for debate too. This could be true up to a point, but once a person reaches a certain level of flexibility it can lead to negative effects (3,4,6). Let me explain.

We have what is known as an active range and a passive range of motion (4). The former refers to the range where we have full control of muscular contraction at this range and the latter is where we can take our muscles/joints (possibly with assistance) but don’t have absolute control. Generally, we will need assistance or a prop to take us here. Think of yourself doing the splits, unless you are a gymnast of course.

If we allow ourselves to go to the end of our passive range this can lead to issues with stability and subsequently increase the injury risk (2,11). As such, a ‘flexible muscle/joint’ is not always a healthier muscle/joint (11,2). However, you can argue that a distinct lack of flexibility could also lead to increased injury risk (3). Like most things, getting the balance is key.

Types of flexibility training

Types of flexibility training

When most think of increasing flexibility they think of static stretching (SS). This can be a useful tool, but there other techniques that you may or may not be aware of. The most recognised of these are dynamic stretching (DS) and Proprioceptive Neuromuscular Facilitation (PNF).

DS is a movement in which there is momentum and a deliberate muscular activation that replicates a movement that the exerciser is going to perform during his session (11).  An example of this would be a walking lunge as the DS and then either the same exercise, but under load or something like a loaded back squat.

PNF (2,11) is generally regarded as a more advanced method of flexibility training and involves a stretch and contraction of either the target muscles or target muscles and their antagonist (the opposite muscle-quad/hamstring). 

*Click here for a full demonstration of both variations.

Benefits of flexibility

Benefits of flexibility

All techniques have their merit and from an anecdotal perspective, I can report success using all 3 variations to good effect. What the general consensus of the research shows is that there is a limited positive association between increased flexibility and injury prevention (2,4).

It also shows a pretty strong correlation between reduced muscle stiffness when any of the closed forms are performed regularly pre and/or post-exercise (5). What it doesn’t show is any significant difference in reducing DOMS (Delayed Onset of Muscle Soreness) (10) regardless of which modality you choose (10). On a purely anecdotal perspective, I see a reasonable amount of improvement of DOMS from SS post-training (next 24 hours), but I suspect this could well be largely a result of a placebo effect.

It also appears to facilitate a feeling of relaxation with most clients, but this tends to happen after 2-4 weeks of consistent stretching (2/3 times a week for 10 mins post-training).

In certain sports flexibility certainly has a significant role. Sports such as gymnastics, diving, weightlifting, martial arts and figure skating require those who take part to have very advanced flexibility (2). However, it is important to realise that although these athletes have this in their active range and as such the injury risk is minimised. It is also important to realise that achieving optimal rather than maximum flexibility is the athlete's aim. Anything past optimal may result in reductions in strength, power and speed (4).

Testing flexibility is something that can be done to a high scrutiny in a lab setting and to a less accurate degree in the gym based setting. Tests such as the ‘sit and reach’ test as well the 'shoulder flexibility' test are both tests most of us have either taken part in or are at least aware of. The ease of administering these tests is fairly high. However, the validity of their use is strongly held into question (7,8,9). Personally, I rarely use any form of flexibility testing with clients for this reason.

My standpoint on flexibility is I am an advocate of increasing a person's range of motion but only to where they have complete control. The majority of people I see are very inflexible and this is inhibitory to their performance in the gym and their overall goals (improving their body shape and health). Once a client reaches a satisfactory level of flexibility I then switch the focus to maintaining this and driving all their efforts to gain strength, building muscle and losing fat.

READ NEXT: Tried and tested remedies and products to help you increase flexibility.

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A Personal Trainer explains the benefits of improving flexibility and how to reach your optimal level to help you exercise better and reach your goals.


1. Committee on Fitness Measures and Health Outcomes in Youth; Food and Nutrition Board; Institute of Medicine; Pate R, Oria M, Pillsbury L, editors. Fitness Measures and Health Outcomes in Youth. Washington (DC): National Academies Press (US); 2012 Dec 10. 7, Health-Related Fitness Measures for Youth: Flexibility. Available from: https://www.ncbi.nlm.nih.gov/books/NBK241323/
2. Acute effects of muscle stretching on physical performance, range of motion, and injury incidence in healthy active individuals: a systematic review. David G. Behm, Anthony J. Blazevich, Anthony D. Kay, Malachy McHugh Applied Physiology, Nutrition, and Metabolism, 2016, 41:1-11.
3. Garber CE, Blissmer B, Deschenes MR, Franklin BA, Lamonte MJ, Lee IM, Nieman DC, Swain DP. American College of Sports Medicine. American College of Sports Medicine position stand. Quantity and quality of exercise for developing and maintaining cardiorespiratory, musculoskeletal, and neuromotor fitness in apparently healthy adults: Guidance for prescribing exercise. Medicine and Science in Sports and Exercise. 2011;43(7):1334–1359.
4. Kay AD, Blazevich AJ. Effect of acute static stretch on maximal muscle performance: A systematic review. Medicine and Science in Sports and Exercise. 2012;44(1):154–164.
5. Kay AD, Blazevich AJ. Moderate-duration static stretch reduces active and passive plantar flexor moment but not achilles tendon stiffness or active muscle length. Journal of Applied Physiology: Respiratory, Environmental and Exercise Physiology. 2009;106(4):1249–1256.
6. Ahlquist A, Hagman M, Kjellby-Wendt G, Beckung E. Physical therapy treatment of back complaints on children and adolescents. Spine. 2008;33(20):E721–E727.
7. Castro-Piñero J, Artero EG, España-Romero V, Ortega FB, Sjostrom M, Suni J, Ruiz JR. Criterion-related validity of field-based fitness tests in youth: A systematic review. British Journal of Sports Medicine.
8. España-Romero V, Artero EG, Jimenez-Pavon D, Cuenca-Garcia M, Ortega FB, Castro-Piñero J, Sjostrom M, Castillo-Garzon MJ, Ruiz JR. Assessing health-related fitness tests in the school setting: Reliability, feasibility and safety; the ALPHA Study. International Journal of Sports Medicine. 2010;31(7):490–497.
9. Freedson PS, Cureton KJ, Heath GW. Status of field-based fitness testing in children and youth. Preventive Medicine. 2000;31(2):S77–S85. 
10. Herbert RD, de Noronha M, Kamper SJ. Cochrane Database of Systematic Reviews. 7. 2011. Stretching to prevent or reduce muscle soreness after exercise.
11. https://people.bath.ac.uk/masrjb/Stretch/stretching_4.html#SEC32

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