Here's a 30-minute strength workout for the gym that targets all major muscle groups. It's important to note that before starting any new exercise routine, it's recommended to consult with a healthcare professional or a certified fitness trainer to ensure it aligns with your personal fitness goals and abilities.

Warm-up (5 minutes): Start with a dynamic warm-up to increase blood flow and prepare your body for the workout. Examples of warm-up exercises include:

1. Jogging or brisk walking on the treadmill for 5 minutes.
2. Arm circles - Stand with your feet shoulder-width apart and extend your arms out to the sides. Make small circles with your arms, gradually increasing the size of the circles.
3. Leg swings - Stand next to a wall or support and swing one leg forward and backward, gradually increasing the range of motion. Repeat on the other leg.

Strength Workout (25 minutes):

1. Squats (4 sets, 8-10 reps): Start with squats to target your lower body, specifically your quadriceps, hamstrings, and glutes. Stand with your feet shoulder-width apart, lower your hips back and down as if sitting into a chair, and then push through your heels to return to the starting position. You can use a barbell, dumbbells, or just your body weight for resistance.

2. Push-ups (3 sets, 10-12 reps): Push-ups are a great compound exercise that primarily targets your chest, shoulders, and triceps. Begin in a high plank position with your hands slightly wider than shoulder-width apart. Lower your chest towards the floor while keeping your core engaged, and then push back up to the starting position.

3. Bent-over rows (3 sets, 10-12 reps): Bent-over rows engage your back muscles, specifically your lats, rhomboids, and traps. Hold a dumbbell in each hand, hinge forward at the hips with a slight bend in your knees, and let your arms hang down. Pull the dumbbells up towards your chest, squeezing your shoulder blades together, and then lower them back down.

4. Overhead press (3 sets, 10-12 reps): The overhead press targets your shoulders, triceps, and upper back. Hold a barbell or dumbbells at shoulder height with palms facing forward. Press the weight directly overhead, fully extending your arms, and then lower it back down to shoulder height.

5. Lunges (3 sets, 10-12 reps per leg): Lunges work your quadriceps, hamstrings, glutes, and calves. Stand with your feet hip-width apart, step forward with one leg, and lower your body until both knees are bent at a 90-degree angle. Push through your front heel to return to the starting position, and repeat on the other leg.

Cool-down (5 minutes): Finish your workout with a cool-down to gradually decrease your heart rate and stretch your muscles. Examples of cool-down exercises include:

1. Walking on the treadmill at a slower pace for 5 minutes.
2. Standing quad stretch - Stand tall, bend one knee, and grab your ankle or foot with the same-side hand. Pull your heel towards your glutes, feeling a stretch in the front of your thigh. Repeat on the other leg.
3. Standing forward fold - Stand with your feet hip-width apart, hinge at the hips, and let your upper body hang forward. Allow your head and neck to relax. Hold for 20-30 seconds.

Remember to listen to your body, use proper form, and adjust the weights or repetitions as needed. It's also essential to rest and recover adequately between workouts to prevent injuries and promote muscle growth.