Deep-water running can maintain run fitness for 4-6 weeks in trained runners; evidence for the elliptical and cycling is much weaker
Interpretation
Two small trials in healthy trained runners agree: VO2max, threshold and economy were maintained over 6 weeks of deep-water running versus treadmill running (Wilber 1996, 16 men), and 5-km time, VO2max and lactate threshold were maintained when deep-water running replaced all running for 4 weeks (Bushman 1997, 11 runners, 10 men, no control). A review (Reilly 2003) concludes trained athletes maintain aerobic performance for up to 6 weeks. Maximal heart rate is lower in water (87.2% of treadmill, Dowzer 1999). Elliptical evidence is one 3-week study in recently trained adults (Joubert 2011), and cross-training transfer never exceeds sport-specific training (Tanaka 1994). Participants were mostly men, healthy rather than injured, and not triathletes.
Practical implication
An injured triathlete cleared by a clinician can use deep-water running, run by effort rather than land heart-rate zones, to hold run fitness for several weeks, while knowing this is extrapolated from small 1990s trials in healthy male runners. Maintained fitness does not mean tissues are ready for impact; return to running gradually.
Sources
6 sources, independently verified.
Six weeks of matched treadmill or deep-water running, 5 days a week, alternating 30 min at 90-100% and 60 min at 70-75% VO2max. VO2max (58.4 to 60.1 vs 58.7 to 59.6 ml/kg/min), ventilatory threshold and running economy did not differ within or between groups. Healthy men, not injured.
Four weeks of deep-water running only (20-24 sessions) replaced land running. 5-km treadmill time (1,142.7 vs 1,149.8 s), VO2max (63.4 vs 62.2 ml/kg/min), lactate-threshold velocity and submaximal oxygen uptake did not change significantly. No control group.
Review: maximal oxygen uptake, ventilation and heart rate are lower in water than on land; blood lactate is higher at matched submaximal oxygen uptake; training studies confirm efficacy, clearest in water-based tests; trained endurance athletes maintain aerobic performance for up to 6 weeks; reduced spinal loading supports injury-prevention use.
In maximal tests, peak oxygen uptake was 75.3% (deep water) and 83.7% (shallow water) of treadmill values, and peak heart rate 87.2% and 94.1%. Authors judged water running an adequate training stimulus.
After 4 weeks of running, 3 weeks of running (n = 7), elliptical training (n = 7) or no training (n = 6). Estimated VO2max fell 0.8%, 1.5% and 4.8% respectively, none significantly; treadmill test time fell significantly only with no training. Very short, recently trained participants, estimated VO2max.
Some transfer of VO2max training effects exists from one mode to another, more noticeable when running is the cross-training mode; swim training may give minimal transfer; cross-training effects never exceed those of sport-specific training; cross-training may be a useful supplement during injury rehabilitation, overtraining or psychological fatigue. Abstract read on Springer; no numerical effect sizes in the abstract.