There are many types of measurable strength – maximal strength, speed-strength, strength endurance, relative strength, starting strength, etc, etc. – that can factor into your sport performance abilities. Training with weights or heavy objects is not the end-goal of too many sports; Power lifting, Olympic lifting, and Strongman being the main exceptions. Training with weights CAN, however, provide protection from injury, allow a greater display of force and/or speed in your sport performance, and improve your general conditioning (GPP) and work capacity. All of these factors lead to improved sport results, and can be improved upon through weight training.
So how do you best fit this into your sport training? Well, we’ve written a book on this and it’s included in the Faster Swimming Manual, so the following description is basic…Our Training recommendations involve lifting heavy weights, lifting moderate weights explosively, and lifting moderate weights for higher repetitions. Heavy lifting increases maximal and starting strength; explosive lifting increases speed-strength and force production; repletion lifting increases strength endurance and work capacity. Relative strength is your strength level in relation to your own body and is addressed in our program in the weight room (pull-ups, dips, hanging leg raise, etc) and in the dryland program – which also focuses on strength endurance, core strength, and to an even greater degree on work capacity and active range of movement. All of these methods will lead to some degree of muscle gain (hypertrophy) which further increases your capacity to produce useable force in your sport. One of the basic principles at work within all of this is that of progressive overload; you must continually and progressively increase loads (poundage and/or speed) to adapt to a higher level.
Injury prevention can also be addressed with weight training. Training with weights in a balanced program will lead to greater overall body-strength and control, which leads to more efficient and coordinated movement which leads to fewer injuries. Specific injury-prone areas for a given sport can also be addressed and strengthened as needed. Using swimming as an example, the shoulders are a frequent site of injury. Injury prevention can be addressed through specific exercises (Cuban press, faces pull, pull-ups, rack pull-ups, pullovers, etc) and through repetition and movement work with bands (internal/external rotation, distraction, etc.).
All of this can be fit into brief (around 1 hour) workouts, done 2-4x per week, to increase your durability and sport performance – which you can learn more about here (link).
So, back to the original question – How strong is “strong enough”? As long as weight training is not interfering with sport practice and/or competition, it is our view that you can always improve performance by getting stronger. Again – the end-goal is increased performance in your sport, and being able to display more force and speed while lessening your chance of injury will lead to this. Combine this type of weight training with appropriate and balanced sport training and you are on your way to improved performance!!