The Effect Of The Tonal Continuous Drop-set Mode On Elbow Flexor Hypertrophy

PURPOSE: This within-participant unilateral design study investigated the effect of resistance training with traditional (TRAD) or continuous drop set (DROP) protocols using the Tonal device on elbow flexor hypertrophy. METHODS: Ten recreationally trained males and females trained for ten weeks, with limbs randomized to either TRAD or DROP conditions. In the TRAD condition, participants performed four sets of standing preacher curls and two sets of kneeling lat pulldowns to momentary failure with 3 minutes of interset rest. The DROP condition performed 3 continuous drop set “series” in each session with the same ratio between exercises; which were designed to elicit a similar total number of repetitions in roughly half the total training time. Elbow flexor muscle thickness (MT) was assessed via b-mode ultrasonography at four time points during the intervention. To compare change in elbow flexor size between TRAD and DROP conditions, a linear mixed effect model with nested random intercepts was constructed for analysis. All estimates were compared to a 68% minimum detectable change (MDC) calculated from the typical error of measurement to aid with interpretation. All hypotheses were tested against a significance level of 0.05. RESULTS: Both conditions resulted in significant (p < 0.001) and practically meaningful improvements in elbow flexor size (TRAD = 0.314 cm [95% CI: 0.255, 0.384]; DROP = 0.215 cm [95% CI: 0.159, 0.273]). The contrast between conditions favored the TRAD condition (p = 0.0085), but was predominantly compatible with negligible magnitudes (TRAD - DROP = 0.0988 cm [95% CI: 0.0188, 0.188], pequiv = 0.3525). The secondary analyses revealed that the DROP condition accumulated similar total volume load and repetitions to the TRAD condition in less than half the total training time (DROP = 6.40 ± 0.66 min; TRAD = 16.70 ± 1.16 min). CONCLUSIONS: The continuous drop-set mode protocol performed on the Tonal device seems to be a time-efficient strategy to elicit meaningful elbow flexor hypertrophy; however, traditional set configurations may offer marginally superior outcomes. It remains unclear if the magnitude of these differences are practically relevant. This study will continue until at least the target number of participants are recruited, in line with our pre-registered a-priori precision analysis. Supported by: This study is funded by the company Tonal.