By Amjad Saleh, Exercise Physiologist
Whenever we start an exercise program we find ourselves asking “how long until I get stronger?” Or if you were me, “how long until I can bench 100 kg?” After reading this article I hope you leave with a little more understanding about what strength means, which exercises are best for improving strength and a brief timeline of the physiological reasons for strength gains.
Strength is the maximal force a muscle or muscle group can generate against a resistance in a single contraction. However, strength testing can be done by measuring one repetition maximum (1RM) up to 10RM just depending on the patient’s goals, type of training program and training experience (i.e. it would be a lot safer to perform a 10RM on an elderly patient with osteoporosis who has never participated in an exercise program).
Progressive Resistance Exercise (PRT) or more simply, weightlifting is the best modality of exercise to increase strength. Exercises need to consist of 3 – 4 sets with 4 – 12 repetitions each set. Resistance at each set needs to be at least 70% of maximal strength and the warm up set of 50 – 60% of maximal strength. Rest periods of at least 30 – 120 sec between sets to allow neuromuscular recovery. Resistance training programs are best performed at least 2 times per week. For example; I conduct a 10RM bench press to measure upper body strength and find my 10RM is 70 kg. Therefore, you will perform 1 – 2 warm up sets at 35 kg x 10 reps (60% of max) then 2 – 3 sets at 55 kg x 8 repetitions (80% of max). Higher repetitions (8-12 reps) will result in more hypertrophy and lower repetitions (4-8 reps) will provide more strength gains. The key is to progressively overload the intensity as strength increases.
So how long does it take to begin to see any strength gains, the short answer is about 2 weeks in the normal, untrained population groups. Timing may not be as straight forward in certain neurological populations due to contractures, spasticity, impaired motor unit activation, central fatigue and many other factors but rest assured that research shows that PRT improves strength in all population groups regardless of disease. Even in the case of a non-functional limb, research has shown strength improvement of 11% by performing strength training on the non-affected limb!
Strength improves firstly due to neural factors followed by structural changes within the muscle. Below outlines the physiological changes that correlate to strength gains over 8 weeks;
1. Neural factors account for approximately 90% of strength gained in the first 2 weeks. Neural strength gains are due to increased efficiency in neural recruitment patterns, increased motor neuron excitability, increased CNS activation, improved motor unit synchronization and decreased neural inhibitory reflexes. Neural adaptions play a particularly important role in strength & power improvements in the elderly.
2. In weeks 2 – 4, strength gains are approximately 50/50 due to neural adaptions and muscle fibre adaptions. In this this period we have more psychologic disinhibition
and learning factors that help improve strength further. i.e. as training progresses, the individual will become more accustomed to equipment and proper form therefore having less fear of injury or unpleasant thoughts that may affect his/her training. This results in less protective inhibition from the CNS allowing greater strength capacity.
3. After about 4 weeks most of the strength gains will be due to muscle fibre adaptions such as hypertrophy. Changes in muscle size are only detectable after at least 3 weeks and the remodeling of muscle architecture precedes gains in muscle cross-sectional area. Resistance training increased protein synthesis and satellite cell proliferation which are essential to muscle hypertrophy. Other physiological changes to muscle structure include an increase in enzymes responsible for creatine and carbohydrate breakdown, increased metabolic rate, increased ligament and tendon strength and an increase in bone mineral density.
If you would like to know more about how strength training can help you then feel free to speak to one of our exercise physiologists today. They can help create an individualised strength program tailored just for you and any condition you may have and even run small groups especially focused on strength training.