If you’ve watched German tennis star Alexander Zverev play a tennis match, it is likely that you will observe him regularly peer into his bag during breaks - leading to rumours that he may be illegally receiving coaching tips via social media.\[1]

![](/img/zverev-diabetes.jpeg "Zverev glances at his kit bag during a tennis match")

Germany’s Davis Cup captain, Michael Kohlmann in an interview with DW (German media) last year stopped such rumours dead in their tracks - “He's always checking his blood sugar level then \[when he looks into the bag]. I sit right there, and I can see exactly what he's doing.”

Zverev has been diagnosed with Type 1 Diabetes since the age of three.

French Open 2023 witnessed a spat between match officials and Zverev as he proceeded to inject his insulin during a match.

"The officials said I need to leave the court," Zverev said after his fourth round win over Grigor Dimitrov on Monday. "During my last match, they told me then this would count as a toilet break."

"I replied: 'Guys, come on! I only have two toilet breaks in a match but in a best-of-five-match sometimes I have to inject four, or five times.'"

"So I told them that it can not be like this because this would mean that something is not allowed what is necessary for my well being, for my life."

"They said it looks weird when I do this on court. If I don't do it, my life will be in danger. But they said it looks weird. This discussion makes no sense."

At the time his diagnosis doctors believed it was impossible for someone with Type I diabetes to reach the highest level of their sport.

"I think today I can rightfully say they were wrong," Zverev said.



**How does Type 1 Diabetes affect the body?**

For people with Type 1 diabetes, the body is unable to produce insulin, leading to an accumulation of sugar as the body’s cells are unable to absorb sugar. This can reduce the level of consciousness or in more severe cases cause diabetic coma (complete loss of consciousness). Thus, it is essential for type 1 diabetics to inject themselves with insulin daily.



**Exercise & Diabetes Management**

Although there is no cure for diabetes, the condition can be very much kept in check.

For an athlete at any level to achieve their full potential, it is vital to get to know their bodies extremely well.  Sport empties the sugar stores in the muscles and liver, and the body must replenish them after any sporting activity.

It's important to take a very close look at how each individual reacts to the respective stresses. Maintaining glucose levels in the normal range is a major challenge during training & competition. The intensity and duration of exercise determines the insulin regimen - eating a meal 1 to 3 hours before exercise, exercising after the peak action of subcutaneous insulin injection, and delaying exercise until glucose and ketones are under control\[2].

Before exercising and depending on the predicted intensity - athletes should modify insulin dosage accordingly. Typically, this reduction ranges from 20% to 50%. A recent table was proposed in order to better adjust carbohydrate intake and insulin dosing (Table 2) \[3].

![](/img/screenshot-2023-09-26-at-5.54.47-pm.png "Extra carbohydrate and insulin adjustment for different physical activity depending on duration and intensity percentage of maximal heart rate")



Taking into account the peak action of each insulin, it has been advised to decrease the dose of the specific insulin that would peak during an upcoming sporting event. For a morning workout, the morning dose of short-acting insulin (regular insulin; onset 1–2 hours, peak 2–4 hours) should be reduced, whereas an afternoon activity requires reduction of the morning dose of intermediate-acting insulin (NPH or lente insulin; onset 1–3 hours, peak 4–10 hours). The physician must understand that some trial and error occurs to meet each individual athlete's insulin and carbohydrate modifications.



**Pitfalls to avoid**

The worst you can do is ‘ignore’ the condition (Type 1 Diabetes). Sports or any another activity should always be dealt wisely and approached not just as a part of your treatment, but also as part of your life.



**References:**

\[1] French Open: Zverev diabetes causes friction, DW, September 2023

\[2] Managing the Athlete with Type 1 Diabetes, Current Sports Medicine Reports 5(2):p 93-98, April 2006.

\[3]\[7] Grimm JJ, Ybarra J, Berne C, et al.: A new table for prevention of hypoglycemia during physical activity in type 1 diabetic patients. Diabetes Metab 2004, 30:465–470.


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