If someone watches you while you train, your performance will improve. This is known as the Hawthorne effect (also referred to as the observer effect), and it’s one of the key benefits of personal training.

The Science Behind Supervised Training

A study published in Medicine & Science in Sports & Exercise examined the impact of direct supervision on strength performance:

The influence of direct supervision of resistance training on strength performance
Mazzetti SA, Kraemer WJ, Volek JS, Duncan ND, Ratamess NA, Gómez AL, Newton RU, Häkkinen K, Fleck SJ.
Med Sci Sports Exerc. June, 2000. 32(6): 1175-84.

Purpose

The study aimed to compare changes in maximal strength, power, and muscular endurance after 12 weeks of periodized heavy-resistance training under direct supervision (SUP) versus unsupervised training (UNSUP).

Methods

• Participants: 20 moderately trained men (average age 24.6 years)
• Groups: Supervised (SUP) vs. Unsupervised (UNSUP)
• Training Program: Both groups followed the same linear periodized resistance training program, progressing through preparatory (10-12 RM), hypertrophy (8-10 RM), strength (5-8 RM), and peaking (3-6 RM) phases using free weights and machines.
• Assessments: Participants were tested on maximal squat and bench press strength (1-RM), squat jump power, bench press muscular endurance, and body composition before and after the 12-week program.

Results

• The supervised group had significantly greater training loads per week for both squat and bench press exercises.
• The rate of strength increase (kg per set) was higher in the supervised group.
• Maximal squat and bench press strength gains were significantly greater with supervision.
• Squat and bench press 1-RM, as well as mean and peak power output, improved in both groups.
• The supervised group showed significant increases in body mass, fat-free mass, and strength gains compared to the unsupervised group.

Conclusion

Direct supervision in resistance training led to greater strength gains and a faster rate of progress than unsupervised training.

Why Supervision Matters

Supervision not only enhances performance but also provides accountability, proper technique correction, and motivation. Even experienced lifters benefit from having someone oversee their training.

To explore why supervision can be so impactful, check out Alex Hutchinson’s article: Will I Get a Better Workout if I Hire a Personal Trainer?.