Hi,
Training with a partner is much better, but not always possible, especially when the intervals are longer and with a higher intensity . If you are hiking, adding weight to the backpack will make you walk at the same pace and intensity as your training partner, if you are running I wouldn’t take any weight but you can always go forwards and backwards in order to stay close to the person you are training with.
Another strategy if you are running, is adding more time to your training before or after you go with your training partner or doing your strength training before( this last one , will make you also more tired and work in higher zones when running )
I hope it helped
Cheers,
Pedro Carvalho