Power vs strength training to improve muscular strength, power, balance and functional movement in individuals diagnosed with Parkinson's disease

Background: Declines in strength and power are cardinal symptoms of Parkinson's disease (PD), a progressive neuromuscular disorder. Progressive resistance training (PRT) has been shown to reduce a wide variety of PD-related motor deficits; however, no study has examined differences between the two most common RT methodologies utilized in this population, high-load, low velocity strength training (ST) and low-load, high-velocity power training (PT). The primary purpose of this study was to compare the effects of ST and PT on measures of strength, power, balance and functional movement in persons with PD. Method: Thirty-five persons with mild to moderate PD (Hoehm and Yahr Stages = 1-3; UPDRS Part III = 30.6 +/- 14.0) were randomized into either a ST or PT group involving 12 weeks of supervised PRT (2 visits per week). Leg press (LP) and chest press (CP) muscular strength (1RM) and muscular peak power (PP) were assessed before and after the twelve week training period as primary outcome measures. In addition, secondary measures of balance (Berg Balance Assessment (BBA), dynamic posturography (DMA), Modified Falls Efficacy Scale (MFES)), functional movement (timed up-and-go), and quality of life (PDQ-39 summary index and Mobility subscore) were obtained at the same time points, given the impact of PD symptoms on fall probability and independence. Results: Repeated measures ANCOVA revealed significant improvements in LP 1RM (M-diff = 54.89 kg, 95% CI: 43.38, 66.40; p < .05; d = 3.38) and CP 1RM (M-diff = 7.33 kg, 95% CI: 4.75, 9.91; p < .05; d = 2.02). Additionally, significant improvements were seen in LPPP (M-diff = 112.27 W, 95% CI: 56.03, 168.51; p < .05; d = 1.42) and CPPP (M-diff = 52.1 W, 95% CI: 23.38, 80.86; p = .001; d = 1.29). No significant improvements were seen for any secondary outcome measures, however BBA scores were shown to significantly decrease following the intervention (M-diff = -1.686, 95% CI: -2.89, -0.482; p = .007 d = -0.96), although this change did not reach clinical significance (clinically meaningful change = +/- 4.0). In addition, the ST group demonstrated significantly poorer PDQ-39(SI) scores (M-diff = 4.96, 95% CI: 0.54, 9.38; p = .029), whereas the entire sample showed significantly poorer PDQ-39(MOB) scores (M-diff = 4.80, 95% CI: 0.17, 9.43; p = .043; d = 0.71). Conclusions: Both ST and PT appear to be effective at reducing the neuromuscular deficits associated with PD; however, the use of these interventions for improving functional performance was not supported.