Developing a powerful, well-balanced lower body requires more than heavy bilateral lifts like squats and deadlifts. Unilateral exercises—movements that train one side at a time—are essential for building muscle symmetry, improving joint stability, and enhancing athletic performance.
They also help correct strength imbalances that can limit bilateral lifts and increase injury risk.
This article examines three of the most effective unilateral lower-body exercises, explains their biomechanical benefits, and provides science-backed programming recommendations to maximize muscle and strength development.
Why Unilateral Training is Critical
Unilateral training offers unique benefits beyond what bilateral exercises can deliver. Research has consistently shown that asymmetries between limbs are common and can affect performance and injury risk. A systematic review by Bishop et al.(2018) found that strength imbalances exceeding 10–15% can impair performance and increase injury susceptibility.
Unilateral movements also place higher demands on stabilizing muscles, particularly in the hips and core, due to the reduced base of support. This is supported by electromyography (EMG) research showing greater gluteus medius activation during single-leg compared to double-leg exercises (Distefano et al., 2009).
Additionally, unilateral training can enhance balance, coordination, and proprioception, which are important not only for athletes but also for general population strength training (Huxel Bliven & Anderson, 2013).
Exercise 1: Bulgarian Split Squat
Biomechanical Overview
The Bulgarian split squat (BSS) is a single-leg squat variation with the rear foot elevated. This position increases the range of motion (ROM) at the working leg’s hip and knee joints while reducing spinal loading compared to bilateral squats.
Biomechanically, the BSS produces high quadriceps activation while also significantly engaging the gluteus maximus and hamstrings, particularly when the torso leans slightly forward (McCurdy et al., 2010). The elevated rear foot also shifts the center of mass forward, increasing knee extensor demand.
Scientific Evidence
Research comparing unilateral squats to bilateral squats shows that the BSS can elicit similar or even greater hypertrophy and strength gains for the working leg. A study by Kipp et al.(2021) found that unilateral squat variations like the BSS matched back squats in quadriceps hypertrophy when training volume was equated.
Furthermore, EMG data indicate high activation of both the quadriceps and gluteals in the BSS, with the added benefit of improved balance and stability through increased activation of hip abductors (Distefano et al., 2009).
Programming Guidelines
- Sets/Reps: 3–5 sets of 6–12 reps per leg
- Load: 65–85% of unilateral 1RM
- Tempo: Controlled eccentric (2–3 seconds) to maximize muscle tension
- Progression: Increase load via dumbbells, kettlebells, or barbell positioning (front rack or back rack)
Exercise 2: Single-Leg Romanian Deadlift (SLRDL)
Biomechanical Overview
The SLRDL targets the posterior chain—primarily the hamstrings and gluteus maximus—while challenging hip stability and proprioception. The movement involves hinging at the hip on one leg while the non-working leg extends backward, maintaining a neutral spine throughout.
Because the movement is performed on one leg, there is an increased demand for hip abductors and adductors to stabilize the pelvis, as shown in EMG research (Bishop et al., 2018).
Scientific Evidence
Hamstring injury prevention is closely linked to eccentric hamstring strength. Opar et al.(2015) demonstrated that eccentric loading increases fascicle length in the biceps femoris, which is protective against strain injuries. The SLRDL provides both eccentric and isometric loading in a functional context.
Additionally, single-leg hinge variations train the glutes in hip extension while reducing axial load, making them joint-friendly alternatives to heavy deadlifts. The balance component also improves neuromuscular coordination, which is associated with reduced fall and injury risk in both athletes and older adults (Muehlbauer et al., 2012).
Programming Guidelines
- Sets/Reps: 3–4 sets of 8–10 reps per leg
- Load: Moderate (50–70% of unilateral 1RM) to maintain technique
- Tempo: 3–4 second eccentric phase for maximal hamstring tension
- Progression: Increase load or add instability (e.g., deficit SLRDL)
Exercise 3: Lateral Lunge (Side Lunge)
Biomechanical Overview
The lateral lunge moves the body in the frontal plane, targeting the adductors, glutes, quadriceps, and hamstrings. This is crucial because most lower-body training occurs in the sagittal plane, leaving lateral hip and thigh muscles underdeveloped.
By stepping laterally and shifting the hips back, the lateral lunge increases hip abduction and adduction loading, which strengthens muscles that stabilize the knee and hip during multidirectional movement (Ebben et al., 2009).
Scientific Evidence
Research indicates that frontal-plane training improves change-of-direction ability and injury resilience in athletes. Dos’Santos et al.(2019) found that strengthening the hip adductors through exercises like lateral lunges can reduce groin strain risk.
The lateral lunge also recruits the vastus medialis oblique (VMO), important for patellar tracking and knee stability, making it valuable for athletes and individuals with a history of knee issues.
Programming Guidelines
- Sets/Reps: 3–4 sets of 8–12 reps per side
- Load: Moderate to heavy (dumbbells/kettlebells)
- Tempo: Controlled descent into lunge, explosive push-off back to start
- Progression: Add load, increase step distance, or use deficit platform
Practical Integration into Training
To maximize results, these three exercises can be integrated into lower-body or full-body sessions 2–3 times per week. An example structure for a lower-body hypertrophy session could be:
- Bulgarian Split Squat – 4×8 per leg
- Single-Leg Romanian Deadlift – 3×10 per leg
- Lateral Lunge – 3×12 per side
This approach ensures all major lower-body muscle groups are targeted across multiple planes of motion while balancing strength, stability, and hypertrophy goals.
Conclusion
Unilateral exercises are not secondary to bilateral lifts—they are a cornerstone of balanced, high-performance lower-body development. The Bulgarian split squat, single-leg Romanian deadlift, and lateral lunge provide a comprehensive stimulus for muscle growth, joint health, and athletic function. Backed by biomechanical analysis and peer-reviewed research, these exercises should be staples in any serious lower-body training program.
Bibliography
- Bishop, C., Turner, A. and Read, P. (2018) ‘Effects of inter-limb asymmetries on physical and sports performance: a systematic review’, Journal of Sports Sciences, 36(10), pp.1135–1144.
- Distefano, L.J., Blackburn, J.T., Marshall, S.W. and Padua, D.A. (2009) ‘Gluteal muscle activation during common therapeutic exercises’, Journal of Orthopaedic & Sports Physical Therapy, 39(7), pp.532–540.
- Ebben, W.P., Fauth, M.L., Garceau, L.R. and Petushek, E.J. (2009) ‘Kinetic quantification of plyometric exercise intensity’, Journal of Strength and Conditioning Research, 23(3), pp.757–764.
- Huxel Bliven, K.C. and Anderson, B.E. (2013) ‘Core stability training for injury prevention’, Sports Health, 5(6), pp.514–522.
- Kipp, K., Kiely, M.T., Giordanelli, M.D., Geiser, C.F. and Suchomel, T.J. (2021) ‘Comparisons between bilateral and unilateral squat training on measures of strength, hypertrophy, and power’, Journal of Strength and Conditioning Research, 35(8), pp.2163–2170.
- McCurdy, K., Langford, G.A., Doscher, M., Wiley, L.P. and Mallard, K.G. (2010) ‘The effects of short-term unilateral resistance training on measures of strength and power’, Journal of Strength and Conditioning Research, 24(1), pp.9–15.
- Muehlbauer, T., Gollhofer, A. and Granacher, U. (2012) ‘Associations between measures of balance and lower-extremity muscle strength/power in healthy individuals across the lifespan’, Gerontology, 58(3), pp.197–203.
- Opar, D.A., Williams, M.D. and Shield, A.J. (2015) ‘Hamstring strain injuries: factors that lead to injury and re-injury’, Sports Medicine, 45(1), pp.23–41.
- Dos’Santos, T., Thomas, C., Comfort, P. and Jones, P.A. (2019) ‘The effect of training interventions on change of direction biomechanics associated with increased anterior cruciate ligament loading: a systematic review and meta-analysis’, Sports Medicine, 49(12), pp.1837–1859.
Key Takeaways
| Exercise | Primary Muscles Targeted | Key Benefits | Recommended Sets/Reps | Progression Methods |
|---|---|---|---|---|
| Bulgarian Split Squat | Quadriceps, Gluteus Maximus, Hamstrings, Hip Abductors | Builds unilateral leg strength, increases ROM, improves balance | 3–5 sets × 6–12 reps/leg | Increase load, change barbell position |
| Single-Leg Romanian Deadlift | Hamstrings, Gluteus Maximus, Hip Stabilizers | Improves posterior chain strength, enhances hip stability | 3–4 sets × 8–10 reps/leg | Increase load, use deficits |
| Lateral Lunge | Adductors, Gluteus Maximus, Quadriceps, Hamstrings | Strengthens frontal-plane movement, reduces groin injury risk | 3–4 sets × 8–12 reps/side | Increase load, extend step distance |
image sources
- Lunge: Gustavo Fring / Pexels
