Here is the full list of all 43 Get Fit With Mel B achievements worth 1,000 gamerscore.
Complete your first workout
Do 1000 press-ups
Do 1000 long-arm crunches
Raised a fitness level by 10
Raise fitness level by 25
Exercise every day for two weeks
Complete 100 reps
Complete 500 reps
Complete 1000 reps
Collect over 350 stars in a Dance Aerobics workout
Do 20 good reps in a row
Do 10 perfect reps in a row
Won a gold medal in a workout
Win a gold medal for all challenges
Burn off a chocolate bar
Burn off a pizza
Burn off a Christmas dinner
Follow the menu every day for a week
Complete a 60 minute aerobics workout with a score over 90%
Practise five different exercises
Create a custom fitness workout
Create a custom aerobics workout
Complete a Fitness workout
Complete a Dance workout
Complete a Cardio Workout
Complete an Advanced Cardio Workout
Complete a Combat Workout
Complete 20 Fitness workouts
Complete 20 Dance workouts
Complete 20 Cardio workouts
Complete 20 Advanced Cardio workouts
Complete 20 Combat workouts
Reach level 60 in any category
Reach level 70 in any category
Reach level 80 in any category
Reach level 90 in any category
Reach level 100 in any category
Reach level 70 in three categories
Reach level 80 in three categories
Reach level 90 in three categories
Reach level 100 in three categories