Calculating training intensities

Heart rate is the number of times the heart beats each minute, measured in beats per minute (bpm). For these training calculations, maximum heart rate is estimated using:

$$\text{Maximum heart rate} = 220 - \text{age in years}$$

The training zones are percentages of this estimated maximum:

Aerobic activity uses oxygen to release energy and supports sustained exercise. Anaerobic activity releases energy without oxygen and is important during short, intense efforts. The zones help select an intensity suited to developing these different capabilities.

To calculate a zone, first find maximum heart rate, then calculate both boundaries. A percentage becomes a decimal by dividing it by 100: for example, 60% becomes 0.60.

Consider a 20-year-old marathon runner aiming to develop aerobic fitness. Their estimated maximum heart rate is:

$$220 - 20 = 200\text{ bpm}$$

Their lower aerobic threshold is:

$$200 \times 0.60 = 120\text{ bpm}$$

Their upper aerobic threshold is:

$$200 \times 0.80 = 160\text{ bpm}$$

Their aerobic training zone is therefore 120–160 bpm. This gives a target range to compare with their heart rate during training, rather than a single heart rate they must maintain exactly. A heart-rate monitor can help them check whether their effort falls within that range.

For an anaerobic target, the same method applies, but the boundaries use 0.80 and 0.90. The 80% boundary is shared by the two zones. Maximum heart rate and the resulting zones are estimates, not exact measurements of an individual’s response.

Adapting a circuit to its fitness aim

Circuit training involves completing exercises at a series of stations. A circuit is not automatically designed for one particular fitness component: its time, rest and content determine what it targets.

Time includes how long the performer spends at each station and how long the whole circuit lasts. Longer periods of repeated activity can emphasise sustaining effort, whereas shorter work periods can allow a focus on demanding efforts.

Rest is the recovery period between stations. Shorter rests reduce recovery and make maintaining repeated effort more demanding. Longer rests allow more recovery before the next demanding exercise. The rest period should suit both the participant and the fitness aim.

Content means the exercises selected for the stations. Choosing exercises that challenge different capabilities changes the purpose of the circuit. For example, repeated manageable resistance exercises can target muscular endurance, while heavier resistance exercises with fewer repetitions can target strength.

These choices need to work together. A circuit intended to develop muscular endurance should provide opportunities for repeated muscular effort, with station times, resistance and rest arranged to support that aim. Changing only the station duration cannot compensate for exercises that do not match the intended fitness component.

Establishing one repetition maximum

In weight training, one repetition maximum, often shortened to one rep max or 1RM, is the greatest weight a performer can lift for one complete repetition of a particular exercise. One repetition includes the complete lifting and lowering movement. The result is specific to the exercise: a performer does not have one universal maximum for every lift.

To establish one rep max, the performer completes one repetition with a selected weight, using equipment such as a barbell or bench-press machine. If successful, they attempt a heavier weight. This process continues until the heaviest weight that can be lifted for one full repetition is identified. If the next weight cannot be lifted successfully, the previous successfully completed weight is the one rep max.

This describes a supervised assessment, not an invitation to attempt maximum lifts independently. Appropriate technique and support, including a spotter when needed, are important.

Using one rep max to choose a training load

Once one rep max is known, a training weight can be calculated as a percentage of it:

$$\text{Training weight} = \text{one rep max} \times \frac{\text{chosen percentage}}{100}$$

If one rep max is measured in kilograms, the calculated training weight is also in kilograms. To identify the 70% boundary, multiply one rep max by 0.70.

For strength/power, use a high weight with a low number of repetitions: above 70% of one rep max, with approximately three sets of 4–8 repetitions. Strength concerns producing force; power concerns producing force quickly.

For muscular endurance, use a lower weight with a higher number of repetitions: below 70% of one rep max, with approximately three sets of 12–15 repetitions. Muscular endurance concerns continuing repeated muscular contractions over time.

The percentage and repetition pattern must match. A relatively heavy load challenges force production, while a lighter load allows more repeated contractions. Expressing the load as a percentage of one rep max also means that two performers with different maximum lifts can train at a similar relative intensity.

• Aerobic: 60–80% of maximum heart rate; multiply by 0.60 and 0.80.
• Anaerobic: 80–90%; multiply by 0.80 and 0.90.
• Express heart-rate answers in bpm. These are estimated zones.

Circuit fitness aims

Adapt all three to the performer and aim:

• Time: duration at stations and of the circuit.
• Rest: recovery between stations.
• Content: exercises chosen to target the intended fitness component.

Weight-training intensity

Establish 1RM by increasing the weight attempted for one complete repetition. Use the heaviest successfully completed lift, not an unsuccessful attempt.

$$\text{Training weight} = \text{1RM} \times \frac{\text{percentage}}{100}$$