Exercise and High BG

If competing I trying to run my bg around 7 / 10 ( Mr Redgraves recommendations ) and am monitoring well before I exercise to try and set off around this mark !!!
So in a 3 day event day one is a short 2 lap blast on mountain bikes around a set coarse.
It is day one that I would like to tell you about my bg was 7.7 . My race partner and I set off to the start at 5pm evening event bg all day was good there was no pressure and you could start in your own time as each section is timed. On arriving at the start 20 mins later I was 13.6 so took 1.5 units of QA as new the race should only take us between 30 to 45 mins and didn’t want to go any higher ( I always have torq gels as hypo stops if needed which is a quicker fix than high bg ) off we go up a slight hill it could only of been minutes and instantly felt for a better word knackered heavy legs everything working overtime burning lungs ect I knew High !!! so after a hard frustrating 47 mins finished and had a bg of 24.6 ????
On longer races when this happens I have more patience and can make up for it at the end – I continually get readings in the 20’s.
So just woundered if you might have any other suggestions for me to try. Dafne is working really well when I am Dafne for example through the week at work I am 5’s 6’s and 7’s yay yes of cause there are highs and lows but I stick to my ratio’s and use the adjustment guidelines ect.

Hi, I would say maybe u need to change ur ratio (increase) when checking between ur exercise at least that way it will bring it down and just keep an eye on ur bg level upto 24h. Are u having any sports drinks in between ur exercise and are u washing ur hands when testing that might have an impact on the results?