Written by Chris Teh

The benefits of strength training have been known for some time with research now confirming why it's essential to include strength training in any exercise program. Resistance or strength training improves sports performance, prevents injury, improves bone density and helps recovery from muscle and joint damage. However, what is the right load to use, how many repetitions are best, and how often should the exercises be performed in a week? In this blog, we will answer these questions and help you understand the reasoning behind the load and dosage we give you.

The main factors to consider when planning to increase muscle strength are:

  • The intensity of training i.e the load lifted appears to be the most important factor for the development of strength. Strength is represented by one-repetition maximum (1RM). This is the maximum weight that a muscle can move with just one repetition. However, the literature suggests that a load of approximately 80-85% of 1RM, so that it limits the exercise to 4-8 repetitions, is best for the development of strength. In practice, lower loads of 60-80% of 1RM are used for 6-12 reps per set. Care needs to be taken not to handle loads that are too heavy and may cause injury. We start with low loads for injury recovery or post-surgery and gradually increase it. 
  •  Progressive overloading of the muscle is needed above the point of what it's used to to continue strengthening.
  •  Muscle size is closely related to strength. Therefore, larger muscles need to be stronger.

Progressive overloading is one of the main principles of strength training. In simple terms, this means changing some of the factors of an exercise program in order to increase its difficulty over time. This leads to a gradual improvement in strength gains as the body adapts to the extra load placed on it. Some of these factors are:

  • increasing the weight/resistance
  • increasing the number of sets or repetitions
  • increasing the time under tension
  • reducing the rest time between sets

Each of these factors can be modified to overload your training progressively and will lead to more significant results. However, it is important to modify only one or two factors at a time as modifying too many at once may result in over-training and lead to injury of the muscles or joints. Let's go through these factors in further detail and apply them to a real-life scenario.

For example, Jack is a 26-year-old male recovering from a recent shoulder injury. He is using a green theraband to perform his shoulder exercises and a 5kg weight to perform biceps curls. He currently performs 8 repetitions and 3 sets of each exercise every second day, at a steady/controlled pace. He is resting for 2 minutes between each set.

1. Increasing the weight/resistance

Increasing the weight/resistance of an exercise will place more load on the joints/muscles and make the exercise more difficult. If Jack has been using a 5kg dumb-bell, we may increase this to 6kg and increase the resistance of the theraband from green to blue.

2. Increasing the number of sets/repetitions

The number of repetitions/sets of an exercise can be adjusted to train strength, hypertrophy (muscle building) or endurance. Generally speaking, 10-12 reps of 3 sets will train strength + hypertrophy whilst performing 15+ reps per set will increase endurance. Jack is performing 8 repetitions and 3 sets of his exercises. We could progress Jack by increasing this to 10-12 repetitions and 3 sets.
In general, low repetitions with a heavy weight increase strength, whereas high repetitions with a low weight increases endurance. Therefore, as repetitions increase there is a transition from strength to endurance, but research shows that high reps and lower weights still achieve strength gains. This is important to consider when an injury, joint damage or age doesn't allow you to increase your load.

3. Increasing the time under tension

There is no evidence to show one singular conclusive method/program that is the best for rehabilitation of hamstring strains. However, there is a general consensus on key elements that should be included in a rehabilitation program that will lead to optimal results. These elements include a combination of strengthening, trunk stability/control, neuromuscular control and sports specific training. It is important that all of the above elements are addressed before any athlete returns back to high-level competition as failing to do so can increase the risk of re-injury.

The rehabilitation of a hamstring strain can be broken down into various “phases” that are progressed as the athlete achieves certain goals.

  • Phase 1-  light running drills, stretching and strengthening exercises for the hamstring. Once goals have been met, move into “phase 2”
  • Phase 2 -  addition of change of direction drills and more difficult strengthening exercises.
  • Phase 3 - weight training and sport-specific drills and eventually return to sport.

4. Reducing the rest time between sets

Time under tension refers to how much time your muscles are put under load during the exercise. Increasing the time under tension requires your muscles to work harder and promotes further growth. Currently, Jack is performing his exercise at a steady/controlled pace. If we wanted to make this even more difficult, we would slow it down further and ask him to perform the exercises at half the speed. Doing exercises slowly makes the muscles work harder, giving you more significant strength gains.

5. How often should you exercise?

Recovery is also an important consideration in a strength training program. Muscle growth and adaptation occur between training sessions and therefore, a rest period is necessary to allow for this. With higher resistance and more intense training, a rest period of 48-72 hours is recommended with best results obtained if strength training is performed 2-3 times a week. However, you can exercise more frequently or even go to the gym daily as long as different muscle groups are worked.

Keep these principles in mind when you're doing your next strength training session. As already mentioned, only change one or two of these factors at a time as changing too many can lead to over-training and ultimately do you more harm than good. We recommend you see your physio, exercise physiologist or personal trainer to help you develop a strength training program so that you exercise effectively and safely.


  1. Bloomfield J et al. 1994. Applied Anatomy & Biomechanics in Sport
  2. Perry Marc, 2018, High reps vs low reps: which is better.
  3. Burd N.A. et al, 2012, Bigger weights may not beget bigger muscles: evidence from acute muscle protein synthetic responses after resistance exercise . Applied Physiology, Nutrition and Metabolism