MySQL 8.0

By using db<>fiddle, you agree to license everything you submit by Creative Commons CC0.
CREATE TABLE excercises (primaryMuscleGroup VARCHAR(255),
                         motionName VARCHAR(255));
INSERT INTO excercises VALUES

( 'Chest'              , 'Dips'                 ),
( 'Chest'              , 'Chest Press'          ),
( 'Chest'              , 'Push Up'              ),
( 'Chest'              , 'Flye'                 ),
( 'Legs'               , 'Squat'                ),
( 'Legs'               , 'Lunge'                ),
( 'Back'               , 'Deadlift'             );

CREATE TABLE fitnessRecords (name  VARCHAR(255), motionName VARCHAR(255));
INSERT INTO fitnessRecords VALUES
( 'John Smith'         , 'Dips'                 ),
( 'Sally'              , 'Squat'                ),
( 'Wallace'            , 'Lunge'                ),
( 'Christoph'          , 'Deadlift'             );

SELECT * FROM excercises;
SELECT * FROM fitnessRecords;


primaryMuscleGroup
motionName


Chest
Dips

Chest
Chest Press

Chest
Push Up

Chest
Flye

Legs
Squat

Legs
Lunge

Back
Deadlift




name
motionName


John Smith
Dips

Sally
Squat

Wallace
Lunge

Christoph
Deadlift


SELECT *
FROM excercises t1
WHERE NOT EXISTS ( SELECT NULL 
                   FROM fitnessRecords t2
                   JOIN excercises t3 USING (motionName)
                   WHERE t2.name = 'John Smith'
                     AND t1.primaryMuscleGroup = t3.primaryMuscleGroup )


primaryMuscleGroup
motionName


Legs
Squat

Legs
Lunge

Back
Deadlift


SELECT *
FROM excercises t1
WHERE NOT EXISTS ( SELECT NULL 
                   FROM fitnessRecords t2
                   JOIN excercises t3 USING (motionName)
                   WHERE t2.name = 'Sally'
                     AND t1.primaryMuscleGroup = t3.primaryMuscleGroup )


primaryMuscleGroup
motionName


Chest
Dips

Chest
Chest Press

Chest
Push Up

Chest
Flye

Back
Deadlift
primaryMuscleGroup	motionName
Chest	Dips
Chest	Chest Press
Chest	Push Up
Chest	Flye
Legs	Squat
Legs	Lunge
Back	Deadlift