Stretching is the subject of almost endless debate amongst coaches, Personal Trainers and injury specialists. Conflicting research combined with personal opinion mean the jury is still out with regards to the full benefits of stretching. This article looks at the concept of stretching, and assesses objectively the current thinking on its positive and negative effects on physical conditioning.
Stretching seems to be an almost permanent fixture in sporting warm ups, and has been for many years. The progressive increase in the range of movement in muscles and joints is considered to be one of the most fundamental aspects of pre-exercise routine. The thinking behind this rationale is that these tissues are likely to undergo frequent stretching as part of the forthcoming activity, so progressive pre-event stretching prepares the tissues for this.
Some competitors like to stretch before exercise, considering it a vital element of a warm up and a preventative measure regarding injuries. However, recent research has shown that this is unlikely to have any effect on the reduction of injury, and can even lead to a reduction on performance. A significant body of evidence now shows that pre–exercise stretching actually reduces performance in strength based activities.
The preferred pre-exercise warm up is cardiovascular exercise – increasing the blood and oxygen flow to the muscles. The muscles can need three or four times the blood flow when exercising, due to elevated oxygen requirements and the need to remove toxins. To warm up for flexibility, the stretches should generally mimic the exercise about to be undertaken. Short runs with exaggerated leg lifts, lifts with lighter weights, gentle swings with a golf club, for example. A warm up for a resistance training session requires activation of the tissues in a slightly different way, such as performing repetitions in a slow, controlled motion with a lighter weight than usually required (around 25-50%).
Recent research by the American College of Sports medicine suggests that pre-exercise stretching can actually hamper performance. The findings reported that stretching damages the muscle proteins, making it impossible to recruit these proteins for later performance. This finding has been reinforced by further studies reporting a decline in muscle contractile force for up to an hour post-stretching. The research highlights a negative correlation between duration of the stretch and the subsequent performance of the muscle – the longer the muscle is stretched, the greater the decline in its performance.
Physiologically speaking, muscle tissues consist of thick and thin actin and myosin contractile filaments. When the muscle contracts, these filaments are connected by ‘cross bridges’, which pull the filaments across each other. The net result of this process is a shortening of the muscle, as you can see for yourself when you contract your bicep muscle group, for example.
Visualise a strong piece of rope, which is actually thinner cord wound together and wrapped around each other. Then it is tacked together with fine cord. It is this fine cord that allows the muscle to move via contraction for the chosen exercise, but unfortunately these same cords are damaged by stretching. For strength training in particular it is well known that the muscles actually do suffer damage to promote growth – but this is not desirable if athletic performance is required. The damage caused during resistance training is slightly different in that it is coupled with a relative hormonal response, which doesn’t occur with simply stretching the muscle beyond its normal range.
Stretching after exercise, particularly weight training, is largely regarded as useful to prevent injury and immobility. Without stretching, the frequently hypercontracted muscles become used to their new shortened state and range of movement. The muscle fibres become tough and inflexible and can often affect posture. Post exercise stretching will actually enhance muscle growth, providing it is performed with care.
The best times to stretch are immediately after a set, and at the very end of the session. By moving along the lactic acid caused by the exercise, stretching can actually prolong the workout by delaying fatigue, and can reduce the onset of DOMS.
Benefits of Stretching
Muscles automatically contract after stretching, due to the action of muscle receptors (spindles), which are a kind of safety mechanism to reduce injury. By regular stretching, this contraction is performed more and more efficiently. Eventually, the receptors permit the greater movement, leading to better sports performance; better training without the receptors inhibiting the muscle action. Comparing the range of movement of a yoga enthusiast and a bodybuilder shows the long term effect of gentle stretching.
Sports injury therapists, such as physiotherapists or massage therapists use many muscle stretching techniques in their work. It is important however to differentiate the stretching used by a therapist and that of a fitness enthusiast. A therapist is using stretching to regain flexibility in an otherwise inflexible body part. The stretching is to return the injured area to normal function, or to re-establish a balance in the muscles. It is common knowledge that many injuries and problems are a result of muscle imbalances and tightness that a therapist may treat with stretches or massage, which is another way of reducing muscle tension and stretching the muscle tissue. Massage is also known to promote blood flow and again aid in toxin removal and speed the healing process.
The general consensus is that stretching does have health and fitness benefits, but the problem is that they are often used wrong or without correct thinking. For the regular fitness enthusiast, the best time to stretch is post exercise – gentle post exercise stretching has been shown to improve toxin removal and retain muscle flexibility. Stretching before a warm up is at best pointless, and at worst downright dangerous – stretching a ‘cold’ muscle has been linked to an increased risk of muscle injury such as tears and strains. If you MUST stretch pre-exercise, perform a gentle warm up of sorts beforehand.
Tips for post exercise stretching
- Stretch after workout, occasionally between sets/exercises if resistance training.
- Keep to within an acceptable range of movement – don’t stretch too far.
- Hold for up to 30 seconds allowing the muscle to relax rather than try to contract.
- Don’t cause discomfort.
- Breathe normally.
- Release the stretch slowly.
- Use a form roller to aid stretching and massage muscle
Types of Stretching
Stretches exercises are divided into specific categories, some more effective or desirable than others:
- Ballistic stretches – using momentum to force a joint past its normal range of movement. Examples are bouncing into a toe touch, or a deeper squat. Ballistic stretches are undesirable and a recipe for injury.
- Dynamic stretches – slow, smooth controlled stretches, such as arm circles or side bends.
- Active stretches – using muscles to hold the stretch position. Difficult to hold for long. Example is the ballerina extending the leg to the front.
- Passive stretches – using another part of the body to hold the stretch. For example, seated and pulling forwards by holding the lower leg. This can be useful after injury to work the injured muscle tissue.
- Isometric stretching – using a partner or a piece of apparatus to facilitate the stretch. A gym towel being used to flex the shoulders or upper arms, for example.
- Proprioceptive neuromuscular facilitation (PNF) – probably the most effective type of stretching, it is a combination of isometric and passive stretching. It is effective because it tires out the fast twitch muscle fibres which contract to resist stretching, and also trains the muscle receptors (spindles) to accept the greater muscle length. PNF stretching is the accepted method of stretching by most professional athletes and clubs, and has been often found to be the most effective by various independent studies. PNF stretching is demanding on the muscles, and should not be carried out intensely. Once or twice a session is sufficient.
The research highlights both positive and negative effects of stretching. Almost all of the negatives however surround the misuse of stretching. A carefully administered stretching routine, performed at the right time and within an acceptable range of movement can improve joint mobility and improve post-exercise recovery time. On the other hand, stretching can be dangerous and lead to a sharp decline in performance if not used correctly.
Perhaps the discovery that will shock the majority is that pre-event stretching has been shown to be almost useless in preventing injury. Pre-event stretching may increase joint mobility, which in turn could lead to reduced injury, but this is merely an indirect consequence – stretching of muscle tissue has been shown to be redundant as an injury-prevention strategy.
The advice is simple – using the guidelines above, liaise with a suitably-qualified professional to work out an effective stretching plan for you. If injured, only use the stretching techniques provided by a suitably-qualified Physiotherapist or Personal Trainer. For general muscle and flexibility maintenance, regular form roller use or a deep-tissue sports massage is an effective way of safely keeping muscles in good condition.