Treadmill

1. A treadmill, comprising:

a tread platform comprising two longitudinal frame bars bilaterally disposed at a bottom side thereof;

a swing unit pivotally mounted at a bottom side of said tread platform and biasable relative to said tread platform between an outer position relatively closer to respective rear ends of said longitudinal frame bars and an inner position relatively far from said rear ends of said longitudinal frame bars; and

two inclination angle adjustment blocks, each said inclination angle adjustment block comprising a core shaft defining an axis line, and a plurality of bearing faces connected to one another and respectively disposed in parallel to said axis line and adapted for selectively supporting said tread platform on a ground, said bearing faces defining with said axis line a respective vertical distance, at least two said vertical distances being different, the core shafts of said inclination angle adjustment blocks being pivotally coupled to said swing unit to support said inclination angle adjustment blocks at an outer side relative to said longitudinal frame bars of said tread platform;

wherein each said inclination angle adjustment block comprises a plurality of petals connected to one another around the core shaft thereof, and the petals of each said inclination angle adjustment block having different sizes.

2. The treadmill as claimed in claim 1 , wherein said swing unit comprises an axle transversely disposed at a bottom side relative to said longitudinal frame bars of said tread platform, said axle having two opposite ends thereof respectively protruding over the respective longitudinal frame bars, and two links extended from the periphery of said axle and respectively pivotally connected to said longitudinal frame bars of said tread platform; said core shafts of said inclination angle adjustment blocks are pivotally mounted on said axle near the two opposite ends thereof.

3. The treadmill as claimed in claim 2 , wherein said swing unit further comprises two cushion members respectively mounted on said axle between said inclination angle adjustment blocks and said links and adapted for stopping against said longitudinal frame bars respectively.

4. The treadmill as claimed in claim 1 , wherein said swing unit comprises two axles disposed at a bottom side relative to said longitudinal frame bars of said tread platform, each said axle having an outer end thereof respectively protruding over the corresponding longitudinal frame bar, and two links respectively extended from said axles and respectively pivotally connected to said longitudinal frame bars of said tread platform; the core shafts of said inclination angle adjustment blocks are pivotally mounted on said axles near the outer end of the respective axle.

5. The treadmill as claimed in claim 4 , wherein said swing unit further comprises two cushion members respectively mounted on said two axles between said inclination angle adjustment blocks and said links and adapted for stopping against said longitudinal frame bars respectively.

6. The treadmill as claimed in claim 1 , wherein each petal of each said inclination angle adjustment block comprises a straight segment defining one said bearing face.

7. The treadmill as claimed in claim 1 , wherein each petal of each said inclination angle adjustment block comprises an arched segment, a straight segment connected between said arched segment and said bent segment, the straight segment of one said petal and the arched segment of one adjacent said petal defining one said bearing face.

8. The treadmill as claimed in claim 1 , wherein said swing unit further comprises two cushion members respectively disposed below said longitudinal frame bars of said tread platform and adapted for stopping against said longitudinal frame bars respectively.