What do we measure?

GRASPOR measures the two most critical factors in an athlete’s performance; Muscle Oxygen & Muscle Activation. Below we will cover what, how and why we measure with GRASPOR.

Even though Muscle Oxygen & Muscle Activation are closely linked individually. They can give us useful information and help us understand what to improve and what the weakness is. 

Muscle Oxygen:

GRASPOR measures the oxygen saturation in your muscles. Oxygen levels in the muscles are critical because oxygen is essential to produce energy in the muscles. Without oxygen, the muscle can only produce energy for a short duration of time. This also means that you stress you muscles with a high load if you work with low oxygen. Therefore, knowing the oxygen level is very useful.

Muscle Oxygen is the balance between oxygen delivery and oxygen consumption in the muscle. Muscle Oxygen varies from person to person, but most people will have values between 50-70% at rest.

Muscle Oxygen vs Pulse oximetry

Pulse oximetry is the oxygen saturation in the arteries, blood oxygen. It only represents the oxygen supply, which is useful for a general health assessment. Its commonly measured with wrist smartwatches or fingertip pulse-oximeter but has no value for training optimization.

Besides measuring oxygen saturation, GRASPOR also measures oxygenated haemoglobin and deoxygenated haemoglobin.

So, when knowing the level of oxygenated haemoglobin and deoxyhemoglobin, you can figure out if it´s the demand or supply that is your limitation.

Deoxygenated haemoglobin example

If you do 6x 6 minutes with stable power during the efforts, see that the Deoxygenated haemoglobin increases, it will indicate that your muscles require more oxygen to produce the energy needed to sustain the power. If the amount of oxygenated haemoglobin is stable, it means that the oxygen demand increases.

Oxygenated haemoglobin example

If you do 6x 6 minutes with stable power output and see that the oxygenated haemoglobin drops during the efforts when the deoxygenated haemoglobin is stable, it often means that the muscles are fatigued. In that case,  the muscles struggle to pull oxygen from haemoglobin cells into the muscles through the capillaries. This indicates a supply issue.

The oxygenated haemoglobin can also tell you if your muscles need higher stress during the warm-up procedure. If you see that the oxygenated haemoglobin increases in the efforts after you completed your warm-up, your body needs efforts with a higher power or longer duration during the warm-up.

How do we measure?

GRASPOR measures Muscle Oxygen by near-infrared spectroscopy, which via LEDs, it shines a light into the muscles tissue. The light is absorbed by the haemoglobin in the muscle tissue. Detectors measure the intensity of the light that is returned.

Since the oxygenated and deoxygenated haemoglobin has different absorption spectra in the near-infrared wavelength range, the muscle oxygen can be calculated.

Muscle Activation:

GRASPOR measures the Muscle Activation of the quadriceps and hamstring.

When you want to perform a movement, your brain needs to send an electrical signal to the muscle. Then another signal is activated over the muscle; this electrical impulse causes the muscle to contract. When the muscle contracts, a movement will happen.

It is the force of this contraction that deliveries the power down into the pedals. On the GRASPOR sleeve, there is an electrode placed on both the front and the back of the leg. These electrodes measure the electrical signal that is triggered over the muscle when activating. We measure the intensity of the signals.

Muscle Activation calibration

Before you start training, you need to calibrate your Muscle Activation.

During the calibration, you need to make a maximal voluntary contraction on both your quadriceps and hamstring. After this, GRASPOR knows your Muscle Activation range from 0-100 per cent, and your level of contraction will be shown in this range.

Why this calibration?

When you fatigue, the intensity of the electrical signal will increase to make your muscle contractions equally as powerful. This means that you can use Muscle Activation to tell if your muscular system is fatigued.

Muscle fatigue day 2-day example

If you for two days in a row perform a 10-minute threshold effort, with a focus on how your Muscle Activation act, you will notice one thing:

On the first day, you do a fully recovered max voluntary contraction in the Muscle Activation calibration. In contrast, the next day, your muscles will be fatigued by the effort from the day before.

So, on day one, you activate your quadriceps 30% and your hamstrings 40% during your 10-minute effort.

On day 2, the Muscle Activation calibration is not done with fully recovered legs. This means that the Max voluntary contraction is not as high as the day before, and the range is not as extensive as the day before.

This means that by day 2, you activate your quadriceps 40% and your hamstring 45% during the 10-minute effort.

The increase in the activation means that your muscles require more energy to activate, though the average power is the same during the 10-minute effort. This leads us back to what we read in the Muscle Oxygen section and why Muscle Oxygen and Muscle Activation is highly related.

Because when the muscle is fatigued, the intensity of the signals increases and requires more energy to produce the muscle contraction.

The imbalance between Quadriceps & Hamstring example:

Since GRASPOR measures the activation level on both Quadriceps and Hamstring, it can help you understand if one of the muscle groups is stronger than the other.

If you start 6x 6 minutes threshold efforts at 30% activation on quadriceps and 40% on hamstrings.

However, then you experience your quadriceps activation increases, so you, after the 4th effort, experience  40% activation on both your quadriceps and hamstrings. This is often a sign that your quadriceps are weak, and you need to improve your quadriceps strength.

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