2016 W2x POL
2016 M8+ St.Paul
2016 LM4- DEN
2016 W8+ Cornell

Biomechanics of technical drills. Part 2.

Biomechanics of technical drills. Part 2.

Here is the further analysis and discussion on biomechanics of technical drills, which started in the previous Newsletter. Fig.1 shows force curves during selected eight drills, described before:

As the catch angle and stroke length increase during the slide progression sequence (from “Arms+Trunk” to “Full length” drills), the peak force increases three times (a), but the forces during the last 30-35deg of the drive remain nearly the same (b). The “force catch slip” (the angle travelled by the oar until the force increases up to a fixed value of 200N as a sum of two oars) is getting nearly three times shorter (c) with slide progression (Table 1 in the attachment), which could be explained by a heavier gearing ratio at longer angles and a more effective “catch through the stretcher” (RBN 2006/09, 2014/04). Contrarily, the catch force gradient up to 70% of maximal force is getting slightly longer because peak forces increase.

Both the best “slip” and “gradient” were found during the “catch only” drill, which confirms its effectiveness for developing a “front-loaded” drive, and during the “quarter slide lift-up” (d). However, in the last case, it is explained by the oar inertia at a very high stroke rate of 67spm, when a rower has to apply high force even before the catch to overcome oar inertia. In all quarter-slide drills, there was a gap in the force curve after the catch (e), which means these drills are the most difficult for coordination of the blade entry and rower’s acceleration.

Fig. 2 shows blade work of the same eight drills, as above, which could be understood as a travel of the blade centre relative to water level. It illustrates the fact discussed in the last Newsletter: at shorter catch angles, the slip is getting longer (worth). (Slip is the blade travel from the catch to the point of vertical angle = -3deg, where the blade is fully buried). This happens because of a higher “skying” of the blade before catch (Fig.2, a), and faster horizontal blade velocity after the catch (Fig.3, a), so the blade travels longer horizontally while entering the water with the same vertical velocity. Contrarily, at the end of the drive, the blade velocity is higher at a longer stroke length (Fig.3, b), so the release slip is getting longer during full-length drills.

Maximal leg velocity increases in the “slide progression” sequence of the drills (Fig.4, a). During the “catch only” drill, the values and pattern of the legs velocity were very similar to that of the full length rowing (b), which means the “catch only” drill helps to develop an effective “front-loaded” drive. The highest peak leg velocity was found in “Legs+Arms” drill, but its pattern was very different: the peak occurred much later towards the end of the drive (c). (The most optimal pattern is a quick leg acceleration at the catch followed by a continuous deceleration during the drive, when contribution of the upper body increases.) Only during this drill, that the Rowing Style Factor was higher than 100% (Table 1 in RBN 2016/12), which means it stimulates “slide shooting”, so the drill “Legs+Arms” cannot be recommended for developing the correct drive pattern.

The last column in the Table 1 below shows Handle Drag Factor HDF (RBN 2011/01), which indicates the feeling of “heaviness” in each kind of rowing. The highest HDF=16.9 was found in the “Push for 10”  – a very short high intensity piece at a high rate of ~ 40spm and full stroke length. This means the “Push for 10” could be recommended for specific strength/power training, and could be more effective for this purpose, than “Power strokes” at low rate (HDF=7.2). Surprisingly, the lowest HDF≈4 was found in “Legs+Arms” and “Feet out” drills – both with low trunk activity. The reason for this phenomenon is not clear yet, and it should be investigated further.

Table 1. Extended biomechanical characteristics of rowing drills (average of four scullers in M4x).