In 2013 I was kindly invited by my colleague Dr. Urs Granacher in Potsdam to give a talk to his institution about science in sport. During my stay we discussed about many aspects of sports science and spent a lot of time talking about bilateral deficit and the fact that there was not much research on assessing it in various populations and also on the effectiveness of various training interventions on this interesting neuromuscular phenomenon. In particular, I was concerned with the amount of training prescriptions characterised by exercises involving two limbs, while most movements are performed with one limb. Also, we discussed how this was relevant for the elderly, as the risk of falls is large for older people and falls occur normally when most of the weight is supported by one leg.
Discussions moved to actions, and the project has been now published on Plos One. The abstract is below and if you want to read the article you can click on the image.
Abstract
The term “bilateral deficit” (BLD) has been used to describe a reduction in performance during bilateral contractions when compared to the sum of identical unilateral contractions. In old age, maximal isometric force production (MIF) decreases and BLD increases indicating the need for training interventions to mitigate this impact in seniors. In a cross-sectional approach, we examined age-related differences in MIF and BLD in young (age: 20–30 years) and old adults (age: >65 years). In addition, a randomized-controlled trial was conducted to investigate training-specific effects of resistance vs. balance training on MIF and BLD of the leg extensors in old adults. Subjects were randomly assigned to resistance training (n = 19), balance training (n = 14), or a control group (n = 20). Bilateral heavy-resistance training for the lower extremities was performed for 13 weeks (3 × / week) at 80% of the one repetition maximum. Balance training was conducted using predominately unilateral exercises on wobble boards, soft mats, and uneven surfaces for the same duration. Pre- and post-tests included uni- and bilateral measurements of maximal isometric leg extension force. At baseline, young subjects outperformed older adults in uni- and bilateral MIF (all p < .001; d = 2.61–3.37) and in measures of BLD (p < .001; d = 2.04). We also found significant increases in uni- and bilateral MIF after resistance training (all p < .001, d = 1.8-5.7) and balance training (all p < .05, d = 1.3-3.2). In addition, BLD decreased following resistance (p < .001, d = 3.4) and balance training (p < .001, d = 2.6). It can be concluded that both training regimens resulted in increased MIF and decreased BLD of the leg extensors (HRT-group more than BAL-group), almost reaching the levels of young adults.
Sports & Fitness Science 
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