The Sit-to-Stand (STS) task is an essential activity of independent daily living. It is commonly transferred into the clinic as five-times STS task (FTSTS) for assessment and prognosis of balance and muscle efficiency in the lower extremities of various populations. Research has shown that for activities such as the STS task, a certain level of attentional demand is required to perform the multiple components of a transitional movement. However, to our knowledge, the changes that occur in body mechanics with greater repetitions and the effects of dual tasking while performing FTSTS are currently unknown. PURPOSE: To determine the effects of dual tasking and multiple repetitions on the FTSTS task in healthy, young adults. METHODS: 10 healthy adults (mean age 24 (4.1) years) participated. Each participant stood up and sat down five times as fast as possible as part of FTSTS assessment. Three trials were completed without a cognitive task (SingleTask) and then with a concurrent cognitive task of counting backwards by 3 starting from a random number (DualTask). Time to complete FTSTS was measured. Impulse (Ns/BW), peak force (N/BW), and power (Nm/BW.s) variables were calculated using ground reaction force measurements. A 2-way ANOVA and paired samples t-test were conducted. RESULTS: Participants took significantly longer to complete FTSTS while dual tasking (8.16 [1.77]s) compared to SingleTask (7.38 [1.08]; p = .05). Concentric impulse significantly increased from 0.55 (0.02) during SingleTask to 0.59 (0.03) during DualTask (p = .022), however, power significantly decreased from 0.99 (0.04) during SingleTask to 0.92 (0.05) during DualTask (p = .017). FTSTS concentric, eccentric, and total impulse significantly increased from 1st to 5th repetition respectively: 0.56 (0.03) to 0.59 (0.03; p = .005), 0.49 (0.03) to 0.56 (0.04; p = .013), 1.05 (0.05) to 1.15 (0.06; p = .006). Also, standing peak force significantly decreased from 1st repetition (1.39 [0.03]) to 5th repetition (1.34 [0.03]; p = .004). The mean peak force standing decreased more from 1st to 5th repetition under SingleTask (1.39 [0.04] to 1.32 [0.03]) compared to DualTask (1.39 [0.03] to 1.35 [0.03]; p = .044). CONCLUSION: The force characteristics are altered by both dual tasking and number of repetitions during the FTSTS task in healthy, young adults.
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