CrossFit: How much weight should I lift? (Part 1)
I get asked all the time “how much weight should I lift?” “Should I be using the prescribed (Rx) weight for this WOD, or should I scale it?” Ultimately it depends on your individual goals and the training phase.
Its worthwhile knowing that strength training imposes a physical stress on your body, and when managed correctly you will see positive adaptations. Physical stress damages muscles tissue and our bodies need adequate rest and recovery to adapt. There are many variables that contribute to the amount of stress being applied. The number of sets, the number of repetitions, the tempo of the exercise, the rest between sets, the weights lifted, and the rest between training session are some key factors. Learning to manage the training stimuli is critical to your success in the box.
How much weight should you really be lifting while performing strength training and do you know if you can Rx (use the prescribed weight) the workout of the day (WOD)?
When deciding what weight to use you should first consider the number of times you are going to be picking that sucker up. One could argue that there is an inverse relationship between the number of reps and the weight being lifted (i.e. as the number or reps decreases the weight will increase). It sounds like an obvious process, but don’t be fooled in thinking that this is a linear relationship or that every athlete is the same. Many other variables including training age, sleep, nutrition, muscle fibre type, rest and recovery will affect the outcome.
Each individual needs to learn his or her individual strengths and weaknesses. Some athletes will excel at lifting heavy weights for low reps, but may suck at lifting lighter weights for high reps. While other athletes who struggle to lift heavy, may have the capacity to move a lighter weight for countless reps. Other elite athletes might be awesome at both. Some athletes might be stronger at pushing exercises and others may be stronger at pulling exercise. Everyone is an individual and hence the need to record your own progress.
One of the main tools I continue to use when selecting a weight for a personal training client is the Poliquin Principles. These principles certainly apply to Crossfitters as CrossFit is a sport of strength.
1. The number of repetitions dictates the load – Table 1 shows some estimated percentages of weight an athlete should be able to lift for a certain number or repetitions. Repetition Max (RM) is used to describe the intensity of the exercise.
In my experience these estimates are pretty accurate for most athletes during a strength training session with adequate rest between sets. These estimates are not accurate for CrossFit WODs as adequate rest intervals do not exist when racing the clock. These valuable estimates can be used to help decide if the prescribed (Rx) WOD weight is beyond an athlete’s current strength capability.
Using the following WOD as an example:
21-15-9
- Dead lift 102/70kg
- Box Jumps 30/24”
Let’s say we have a female member with a 1RM deadlift of 75kg. Using the estimations, we calculate that she will only be able to deadlift 70kg for her 2RM (75kg x 94.3% = 70kg). She must lower the weight for this workout. “What weight should I use?” I hear her ask. This depends on her training goal. Is she training to get stronger, or is she training for body composition goals?
2. The number of repetitions for a given time under tension dictates the training effect – Obviously everybody wants to be able to complete the WOD with the prescribed weight. But when this weight is beyond and athlete’s capability they MUST learn to scale it (an injured athlete gets zero results). By using the RM percentages we can estimate our female client should be able to lift:
9RM = (75kg * 76.5%) = 57.38kg
15RM = (75kg * 66.2%) = 49.65kg
20RM = (75kg * 60.6%) = 45.45kg
The question remains, is this member training for strength gains or body composition improvements?
- Improvements in neural adaptations and maximal strength are achieved by a lower number of repetitions performed with a heavy weight.
- Improvements in muscular adaptation and greater gains in strength-endurance are best achieved with higher repetitions performed with a medium to light weight.
Note: Body composition is the ratio of lean muscle mass to body fat (your body fat percentage). If your goals are body composition focused your aim is to build/maintain lean muscle mass and burn body fat (point b. above)
If the client’s goal is to improve her strength she might consider using a weight close to her 9RM. She will obviously need to break the larger sets (21,15) into smaller more manageable chunks (maybe sets of 5-6reps) with a small amount of rest between each chunk. Yes, the WOD will take longer to complete and she might not put the fastest time on the board. At the end of the day it’s not always about the clock! Is lifting a lighter weight for a shorter period of time going to deliver the best strength gains?
If her goal is more body composition driven she might consider using a weight somewhere between her 15-20RM estimates. This will allow the athlete to perform a higher number of reps before needing to put the bar down. This time her WOD will be faster, but her strength gains will not be as significant.
The Training Phase
Just because your primary goal is body composition does not mean you should never lift heavy weights for low repetitions. In physics Work = Force x Distance, and the more work you can accomplish the quicker you will achieve your body composition results. Adding phases of strength training into the programme will increase force production and allow for a higher volume of work to be accomplished in the following phases of training. Remember, only muscle can generate force, fat does sweet FA. You want to loose some body fat? Get stronger!
On the opposite side of the coin a strength athlete should also practice moving light-medium weights with speed. Strength is about force production and the weight lifted is only part of the equation. Force = Mass x Acceleration and hence both the weight (mass) and speed (acceleration) factor can be trained to increase force output. If CrossFit is your sport you need to practice moving large loads over long distances as efficiently as possible.
Switching the training phase from accumulation (high repetitions) to intensification (lower repetitions) keeps the body guessing and prevents stagnation. Our bodies quickly adapt to the training stress and if we are going to continually make gains the training protocol must change.
Take away points
There are a number of factors that can affect the amount of weight we can lift. Every athlete will have his or her good days and bad days in the gym, so don’t be too hard on yourself. We all have our own strengths and weaknesses. Your deadlift might be better than your training partner’s, but their back squat might be better than yours. You need to start paying attention to the weights you have lifted and make a note of these. What is measured can be improved and these figures can be used to estimate the weights you should be lifting during each phase of your training programme.
Always remember to train with a purpose. What are your goals? The competitive side of CrossFit is an awesome motivational tool and we all know how much harder we work when we race the clock. Do your best to select a weight that is going to challenge you and deliver the results you are striving for. Do not be afraid to change the weight during the workout if it is too heavy. Technique comes before intensity and volume and I will cover this very point in part 2.
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