The effect of test modality on dynamic exercise biomarkers in children, adolescents, and young adults.

Cardiopulmonary exercise testing (CPET) modalities, treadmill (TM), and cycle ergometer (CE), influence maximal gas exchange and heart rate (HR) responses. Little is known regarding CPET modality effect on submaximal biomarkers during childhood and adolescence. Ninety-four healthy participants (7-34 y.o., 53% female) performed TM and CE CPET to address two major gaps: (1) the effect of modality on submaximal CPET biomarkers, and (2) estimation of work rate in TM CPET. Breath-by-breath gas exchange enabled calculation of linear regression slopes such as V˙ O2 /ΔHR and Δ V˙ E/Δ V˙ CO2 . Lean body mass (LBM) was measured with dual X-ray absorptiometry. We tested a novel TM CPET estimate of work rate based on TM velocity2 , incline, and body mass (VIM). Like the linear relationship between V˙ O2 and work rate in CE CPET, V˙ O2 increased linearly with TM VIM. TM Δ V˙ O2 /ΔHR was highly correlated with CE (r = 0.92), and each increased substantially with LBM (P < 0.0001 for TM and CE). Δ V˙ O2 /ΔHR was to a small (~8.7%) but significant extent larger in TM (1.6 mL/min/beat, P = 0.04). In contrast, TM and CE Δ V˙ E/Δ V˙ CO2 decreased significantly with LBM, supporting earlier observations from CE CPET. For both CE and TM, males had significantly higher Δ V˙ O2 /ΔHR but lower Δ V˙ E/Δ V˙ CO2 than females. Novel TM CPET biomarkers such as ΔVIM/ΔHR and ∆ V˙ O2 /ΔVIM paralleled effects of LBM observed in CE CPET. TM and CE CPET submaximal biomarkers are not interchangeable, but similarly reflect maturation during critical periods. CPET analysis that utilizes data actually measured (rather than estimated) may improve the clinical value of TM and CE CPET.

Does transcutaneous electrical nerve stimulation improve the physical performance of people with knee osteoarthritis?

BACKGROUND: : According to a recent metaanalysis study, there is strong evidence to support the view that transcutaneous electrical nerve stimulation (TENS) is an effective treatment for managing osteoarthritis (OA) knee pain. However, there is limited evidence showing its effectiveness in improving physical function. This study examined whether TENS alone can improve physical function in terms of range of knee motion and the Timed-Up-and-Go Test. METHODS: : Subjects were randomly allocated into 2 groups receiving TENS at 100 Hz or a placebo TENS. Outcome measures included: 1) visual analog scale for measuring the intensity of the present pain, 2) Timed-Up-and-Go Test, and 3) range of knee motion (ROM). Repeated-measures analysis of variance and Pearson correlation were used for data analyses. RESULTS: : By day 10, TENS produced a significantly greater increase in maximum knee ROM than the placebo group (P = 0.033). TENS also significantly increased the pain-limited knee ROM across sessions, but the between-group difference was short of significance (P = 0.067). The decrease in time in performing the Timed-Up-and-Go Test was also not significantly different between the 2 groups. A moderate correlation was observed between the reduction in pain scores and the improvement in the Timed-Up-and-Go Test. CONCLUSIONS: : Our findings suggested that TENS did improve some of the physical parameters but over 10 days was unable to produce significant improvement in functional performance among people with knee OA. A larger-scale study with the assessment of other functional outcomes may be required to clarify if TENS could improve function in people with knee OA. Also, exercise can be considered to be an important adjunct treatment to TENS to improve function significantly.

Optimal stimulation frequency of transcutaneous electrical nerve stimulation on people with knee osteoarthritis.

OBJECTIVE: This is a double blind study that examined the optimal stimulation frequency of transcutaneous electrical nerve stimulation in reducing pain due to knee osteoarthritis. SUBJECTS: Thirty-four subjects were randomly allocated into 4 groups receiving transcutaneous electrical nerve stimulation at either: (i) 2 Hz; (ii) 100 Hz; (iii) an alternating frequency of 2 Hz and 100 Hz (2/100 Hz); or (iv) a placebo transcutaneous electrical nerve stimulation. METHODS: Treatment was administered 5 days a week for 2 weeks. The outcome measures included: (i) a visual analogue scale; (ii) a timed up-and-go test; and (iii) a range of knee motion. RESULTS: The 3 active transcutaneous electrical nerve stimulation groups (2 Hz, 100 Hz, 2/100 Hz), but not the placebo group, significantly reduced osteoarthritic knee pain across treatment sessions. However, no significant between-group difference was found. Similarly, the 3 active transcutaneous electrical nerve stimulation groups, but not the placebo group, produced significant reductions in the amount of time required to perform the timed up-and-go test, and an increase in the maximum passive knee range of motion. CONCLUSION: Our findings suggested that 2 weeks of repeated applications of transcutaneous electrical nerve stimulation at 2 Hz, 100 Hz or 2/100 Hz produced similar treatment effects for people suffering from osteoarthritic knee.