Vibration as an exercise modality: how it may work, and what its potential might be

Whilst exposure to vibration is traditionally regarded as perilous, recent research has focussed on potential benefits. Here, the physical principles of forced oscillations are discussed in relation to vibration as an exercise modality. Acute physiological responses to isolated tendon and muscle vibration and to whole body vibration exercise are reviewed, as well as the training effects upon the musculature, bone mineral density and posture. Possible applications in sports and medicine are discussed. Evidence suggests that acute vibration exercise seems to elicit a specific warm-up effect, and that vibration training seems to improve muscle power, although the potential benefits over traditional forms of resistive exercise are still unclear. Vibration training also seems to improve balance in sub-populations prone to fall, such as frail elderly people. Moreover, literature suggests that vibration is beneficial to reduce chronic lower back pain and other types of pain. Other future indications are perceivable

Cerebrovascular Hemodynamics, Postural Stability, Gait Dynamics, and Falls in Older Adults

Injurious falls in community-living older adults are associated with standing up suggesting that cerebral hypoperfusion following a postural transition might be a contributing factor. A large population study has recently indicated that one fifth of older adults do not fully recover BP after standing from a supine posture. The purposes of this thesis were to provide a comprehensive assessment between posture-related cerebral hypoperfusion and impaired postural stability, altered gait and falls in older adults. This thesis measured arterial blood pressure regulation and cerebral tissue oxygenation (tSO2) during orthostatic stressors including 3 different transitions to standing in older adults (n=77, ages 69-100 years, average = 86.6±6.6 years) and 2 different transitions to walking in a sub-group of these older adults (n=27, ages 71-101 years, average = 86.8±5.3 years). Primary results included the finding that, like the altered blood pressure responses, 19.5% of older adults had low tSO2 on standing, and they had poorer postural stability. It was also found that a brief 10-s sitting-pause time improved tSO2 and postural stability when performing a supine-sit-stand. Prospective tracking of older adults for 6-months revealed a trend to an increased likelihood of a future fall in those who had the greatest drop in tSO2 on standing. Older adults with low tSO2 (≤60%) during walking had compromised gait dynamics (increased step-step variability). Although gait speed was not directly related to reduced tSO2, the increased mean gait cycle time and stance time associated with changes in OxHb of the older adults with low tSO2 were significantly associated with reduced gait speed. Increased vascular stiffness was associated with lower CBF and altered cerebrovascular hemodynamics while walking as well as lower gait speed. Collectively, the findings from these two investigations support a relationship between cerebral hypoperfusion induced by transitions from supine to upright posture and compromised standing and walking stability with consequences for increased fall risk

Neuromuscular and mobility responses to a vibration session in hypoxia in multiple sclerosis

The aim of this study was to investigate the acute effects of vibration training (WBVT) under hypoxic and normoxic conditions on the voluntary rate of force development (RFD), balance and muscle oxygen saturation (SMO2) in persons with Multiple Sclerosis (MS). 10 participants completed the study (30 % males, 44.4±7.7 years, 164.3±8.9cm, 65.2±11.1kg, 2.5±1.3 Expanded Disability Status Scale, 24.1± 4.0 kg.m− 2 BMI). Maximal force, RFD during isometric knee extension, static balance with eyes open and closed and sit-to-stand test were evaluated before and immediately after one session of WBVT (12 60-s bout of vibration; frequency 35Hz; amplitude 4mm; 1-min rest intervals) under both normoxic and hypoxic conditions. In addition, SMO2 of the gastrocnemius lateralis was assessed during each condition. No changes were found in force, static balance and sit-to-stand test. Time-to-peak RFD increased in the left leg (p = 0.02) and tended to increase in the right leg (p = 0.06) after the hypoxic session. SMO2 resulted in significant increases from the initial to final intervals of the WBVT under both hypoxic and normoxic conditions (p < 0.05). Increases in SMO2 during WBVT demonstrates muscle work that may contribute to the observed muscle adaptations in long-term WBVT programs without inducing decreases in neuromuscular activation, physical function and balance within a session

THE RELATIONSHIP BETWEEN MUSCULOSKELETAL STRENGTH, PHYSIOLOGICAL CHARACTERISTICS, AND KNEE KINESTHESIA FOLLOWING FATIGUING EXERCISE

Fatiguing exercise may result in impaired functional joint stability and increased risk of unintentional injury. While there are several musculoskeletal and physiological characteristics related to fatigue onset, their relationship with proprioceptive changes following fatigue has not been examined. The purpose of this study was to establish the relationship between musculoskeletal and physiological characteristics and changes in proprioception, measured by threshold to detect passive motion (TTDPM), following fatiguing exercise. Twenty, physically active females participated (age: 28.65 ± 5.6 years, height: 165.6 ± 4.3 cm, weight: 61.8 ± 8.0 kg, BMI: 22.5± 2.3 kg/m2, BF: 23.3 ± 5.4%). During Visit 1, subjects completed an exercise history and 24-hour dietary questionnaire, and body composition, TTDPM familiarization, isokinetic knee strength, and maximal oxygen uptake/lactate threshold assessments. During Visit 2, subjects completed TTDPM and isometric knee strength testing prior to and following a fatiguing exercise protocol. Wilcoxon signed rank tests determined TTDPM and isometric knee strength changes from pre- to post- fatigue. Spearman’s rho correlation coefficients determined the relationship between strength and physiological variables with pre- to post-fatigue changes in TTDPM and with pre-fatigue and post-fatigue TTDPM in extension and flexion (α=0.05). No significant differences were demonstrated from pre-fatigue to post-fatigue TTDPM despite a significant decrease in isometric knee flexion strength (P<0.01) and flexion/extension ratio (P<0.05) following fatigue. No significant correlations were observed between strength or physiological variables and changes in TTDPM from pre- to post-fatigue in extension or flexion. Flexion/extension ratio was significantly correlated with pre-fatigue TTDPM in extension (r=-0.231, P<0.05). Peak oxygen uptake was significantly correlated with pre-fatigue (r=-0.500, P<0.01) and post-fatigue (r=-0.520, P<0.05) TTDPM in extension. No significant relationships were demonstrated between musculoskeletal and physiological characteristics and changes in TTDPM following fatigue. The results suggest that highly trained individuals may have better proprioception, and that the high fitness level of subjects in this investigation may have contributed to absence of TTDPM deficits following fatigue despite reaching a high level of perceptual and physiological fatigue. Future studies should consider various subject populations, other musculoskeletal strength characteristics, and different modalities of proprioception to determine the most important contributions to proprioceptive changes following fatigue